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Subsections

Parasites and Protozoa

A great deal of chronical diseases is caused by parasites and pathogenic protozoa due to consumption of infected water and foods, mainly in underdeveloped countries.


Endamoeba histolytica

The vegetative form of Endamoeba histolytica is motile and uninucleate. It multiplies by fission and is able to invade the mucosa of the large intestine where it causes ulcerations.

The invasion of the mucosa of the colon takes place by using histolytic enzymes what gave the name to the species. It comes to abscesses and destruction of the intestinal capillarities raspberry red bloody stool is the result.

It may be carried to the liver, lung or brain and causes abscesses in those organs.
In the intestine, the ameboid form may develop into cyst, a spherical body containing four nuclei and one or more rod shaped chromatoid bodies.Cysts are resistant to chemical and physical agents.

Ninety per cent of infected people are not obviously ill. Only about 10 per cent have active dysentery, discharging trophozoites (motile cells).AS trophozoites die outside of the body and are killed by gastric juice and bile if they are ingested, the disenteric cases are not important as source of infection. The cysts however are able to survive for sometime outside the body and can pass uninjured through the alimentary canal to the ileum. Here each cyst gives rise to eight small infective trophozoites.

Important source of infection are cyst passers which do not have signs of any disease but produce great amount of cysts which are spread by contaminated food and polluted water. If polluted water is used to irrigate plantations of vegetable and salads and human faecis are used as fertilizer the spread of Endamoeba histolytica can take place in large group of persons. Imported vegetables and salads should therefore carefully rinsed or better cooked when the origin of it is unknown.

With modern logistic service throughout the world, contaminated food can easily be imported from the most exotic parts of the world. Amebiasis is considered to be a tropical disease however occasional epidemics in the temperate zone are possible. The cyst-passers state is common in all parts of the world. About 10% of Americans are carriers.Also in Germany cyst carriers of Endamoeba histolytica are present. The incidence is highest in areas where sanitation is poor.

In concentration camps, prisons and in homes with poor sanitation like favelas direct transfer and flies spread the disease. [1].


Prophylaxis of amebiasis

Improve the sanitary facilities, boil the infected water before drinking, avoid ingestion of infected vegetables, cook all meals and make combat to flies.

It is obvious that there must be a decline of resistance of the human body to open the way to an infection. It is also admitted that warm climate rises the disposition to the disease. Other factors which help the eclosion of the disease are bacterial infections, disorders of nutrition and cold. Endamoeba histolytica was first seen and described in feces of diseased persons in 1875 by Lösch.
The disease in Germany is also known as Amöbenruhr called after the region around the river Ruhr in Germany where great epidemics took place around 1875.

Other amebae


Endamoeba gingivalis

It is harmless and lives around gums and teeth.


Endamoeba hartmanii

Is a small ameba which may live in the intestines producing subclinical or mild infections.


Dientamoeba fragilis

Is an intestinal form causing infections.It is not common.


Endamoeba coli

It is not pathogen.


Endolimax nana

It is not pathogen.


Iodameba bütschlii

It is not pathogen.

Free-living amoebae as human pathogens

Free-living amoebae belonging to the genus Acanthamoeba are the causative agents of granulomatous amoebic encephalitis (GAE), a fatal disease of the central nervous system (CNS), amebic keratitis (AK), a painful sight-threatening disease of the eyes, cutaneous lesions and sinusitis in AIDS patients and other immunocompromised individuals.

Spiny surface structures called acanthopodia distinguish Acanthamoeba from other free-living amoebae that infect humans, such as Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea

Cysts are resistant to biocides, chlorination, and antibiotics and survive low temperatures (0 to 2°) Meisler et al., however, have shown that treatment with Freon or methylene oxide or autoclaving destroys cysts. Excystment occurs when trophozoites emerge from the cyst under suitable environmental conditions.

Mazur et al. demonstrated that cysts retained viable amoebae for over 24 years after storage in water at 4° and were tested for pathogenicity by intranasal inoculation of mice. Fewer deaths were recorded for mice inoculated with amoebae which had been encysted for 24 years than for mice inoculated with the same environmental isolates when tested initially.

Marciano-Cabral and Cabral 2003 conclude that it is becoming increasingly apparent that free-living amoebae cause human disease. Furthermore, with increasing awareness of the potential of free-living amoebae to cause disease, amoebae from other genera may be found to be causative agents of human infections. [2]


Primary amoebic meningoencephalitis kills 10 in Pakistan

Primary amoebic meningoencephalitis caused the death of 10 Pakistan in the city of Karachi from March to September. According to the WHO people don't usually get the brain-affecting form of the disease by drinking water, but by swimming in dirty water or cleaning their nostrils with contaminated water. From the nostrils, the parasite (Naegleria fowleri) travels to the brain where it destroys tissue. [3]

Symptoms include fever, nausea, vomiting, stiff neck and headaches. The amoeba, Naegleria fowleri, lives in warm, unclean water. It can infect the human nervous system, though this occurs rarely. In those cases it is difficult to treat and can lead to death in about a week, says Musa Khan, in charge of WHO's Disease Early Warning System in Pakistan.

The disease has killed people in other countries as well. About 300 cases of Primary Amoebic Meningoencephalitis (PAM) have been reported in the world, mostly in USA, Australia, and Europe. These infections are nearly uniformly fatal with only few survivors of PAM reported. [4]

Free-living amoebae are widely distributed in soil and water. Small number of them was implicated in human disease: Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris and Sappinia diploidea. Some of the infections were opportunistic, occurring mainly in immunocompromised hosts (Acanthamoeba and Balamuthia encephalitis) while others are non opportunistic (Acanthamoeba keratitis, Naegleria meningoencephalitis and some cases of Balamuthia encephalitis). Although, the number of infections caused by these amoebae is low, their diagnosis was still difficult to confirm and so there was a higher mortality, particularly, associated with encephalitis. [5]

In 2010 a case of Primary amebic meningoencephalitis (PAM) in Minnesota after freshwater exposure occurred 550 miles north of the previously reported northernmost case in the Americas. Kemble et al advert clinicians to be aware that Naegleria fowleri-associated PAM can occur in areas at much higher latitude than previously described. [6]

Vaccine to treat Naegleria fowleri infection [7]

Kim et al. 2012 evaluated the immune responses as DNA vaccination in Naegleria fowleri infection unsing nfal vaccination. The nfa1 gene of N. fowleri is located on pseudopodia and plays an important role in the pathogenesis of Naegleria fowleri. The authors suggest that this method may become a treatment of Naegleria fowleri infection.

Image fowleri
Picture: Life cycle Naegleria fowleri
http://www.dpd.cdc.gov/dpdx/HTML/FreeLivingAmebic.htm
Life cycle Naegleria fowleri
Naegleria fowleri has three stages in its life cycle: cysts 1, trophozoites 2, and flagellated forms 3. The trophozoites replicate by promitosis (nuclear membrane remains intact). Naegleria fowleri is found in fresh water, soil, thermal discharges of power plants, geothermal wells, and poorly-chlorinated swimming pools. Trophozoites can turn into temporary non-feeding flagellated forms which usually revert back to the trophozoite stage. Trophozoites infect humans or animals by penetrating the nasal mucosa 5 and migrating to the brain 6 via the olfactory nerves causing primary amebic meningoencephalitis (PAM). Naegleria fowleri trophozoites are found in cerebrospinal fluid (CSF) and tissue, while flagellated forms are occasionally found in CSF. Cysts are not seen in brain tissue.

Acanthamoeba

Acanthamoeba lenticulata causes cutaneous lesions and sinusitis in AIDS patients and other immunocompromised individuals. Disseminated acanthamebiasis (DA), which is defined as widespread extracerebral disease, is extremely rare, but its incidence has increased in recent years such as occurred on account of organ transplants such as lung and kidneys.

Marciano-Cabral 2007 reports a fatal case of disseminated acanthamebiasis in a heart transplant recipient and identify Acanthamoeba lenticulata (genotype T5, commonly found in the environment) as the cause of disease. Disseminated acanthamebiasis is difficult to diagnose, being made postmortem in most of the cases. [8]

Acanthamoeba spp. are free-living amoebae found in soil, water, air, humans, and various animals. All known species of Achantamoeba spp are listed in the Taxonomy Browser of NCBI:
http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=5754


Giardia lamblia

Giardia lamblia is a pathogenic protozoa living in the duodenum often without symptoms. Giardia lamblia adheres to the surface of the epithelian cells of the mucosa of the duodenum.
When millions are present the mucosa is completely covered. Fat absorption and digestion is disturbed. Dietary deficiency, diarrhea and bad smelling flatulence takes place.
The disease is spread over cysts in Water and foods.

Coinfections of Giardia intestinalis and Helicobacter pilori

The protozoan parasite Giardia intestinalis and the pathogenic bacterium Helicobacter pylori, both in association are found infesting concomitant in high number of mostly children in densely populated regions. [9]

Ankarklev et al. 2012 examined children living in urban Kampala, Uganda, Giardia intestinalis was found in 20.1% of the children. Helicobacter pylori was found in 44.3% children with a 3-fold higher risk of concomitant Giardia intestinalis and H. pylori infections compared to non-concomitant infections.

Giardia intestinalis multi-locus genotyping (MLG) analysis found assemblage B to be the most frequent Giardia infestation in Kampala children. The assemblage B was highly variable without association with Hellicobacter pilori but presents a risk factor for concomitant infections.

Giardiasis in U.S.A. [10]

Giardia lamblia is a protozoan which is also known as Giardia lamblia or Giardia duodenalis. Giardiasis does not spread via the bloodstream, nor does it spread to other parts of the gastro-intestinal tract. It remains confined to the lumen of the small intestine.

Giardiasis is a nationally notifiable gastrointestinal illness. Yoder analysed the reported cases of giardiasis through CDC's National Notifiable Diseases Surveillance System. In the period of 2009 until 2010 there was a slight increse of number of cases which peaked during early summer through early fall, with higher frequency in northern states. The highest frequency of Giardiasis was found in young children. This may have its origin in higher contact with contaminated water or ill persons.


Cryptosporidium

Oocysts of Cryptosporidium are widespread in the environment and can be found in lakes and streams. It is found in North America and Caribian islands, infesting animals which just had been born and adult animals which produce oocysts and serves as a source of infection for neonates.

Breakdowns of public sewage systems have occasionally resulted in community outbreaks of cryptosporidiosis. Diarrhea, some weight loss and abdominal cramping are the sign of the disease. Many cases of cryptosporidiosis are caused by contamination by pet animals or by contact with other humans.


Balantidium coli

It is a very large protozoan which may cause severe ulcerations of the large intestine. Cysts and motile forms are found in feces. Hogs harbor commonly Balantidium coli.Infection of men is caused by contaminated food and water.

Importance of Giardia and Cryptosporidium in water manegement [11]

From approximately 40 names of Giardia spp only five to six morphologically distinct species are recognised. Giardia lamblia (=G. intestinalis, =G. duodenalis) infect humans and other mammals, Giardia muris is found from other mammals, Giardia ardeae and Giardia psittaci from birds, Giardia agilis from amphibians and Giardia microti from voles. Recent studies demonstrated genetic heterogeneity among Giardia isolates and brought a better understanding of the role of wild and domestic animals as sources of human infection.

Genotypes of Giardia duodenalis [12]

According to Caccio and Rian there are seven genetic groups within the species Giardia duodenalis identified by molecular assays. The groups A and B are found in both humans and animals, and the remaining groups C to G are host-specific. Sequence-based surveys have identified a number of genotypes within assemblages A and B in animal species which may be infectious to humans.

Eimeria

Eimeria is a genus of parasites that includes various species responsible for the poultry disease coccidiosis.

Human infections

Five genera are known to cause infections in humans: Cryptosporidium, Cyclospora, Isospora, Sarcocystis and Toxoplasma. Of these the first three normally are confined to the gastrointestinal tract and cause diarrhoea and abdominal pain. The other two invade the body tissues and many be found in multiple organs. [13]

Coccidiosis [14]

Coccidiosis is a parasitic disease of the intestinal tract of animals, caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue. Diarrhea, which may become bloody in severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic; however, young or immuno-compromised animals may suffer severe symptoms, including death.

While coccidian organisms can infect a wide variety of animals, including humans, birds, and livestock, they are usually species-specific. One well-known exception is toxoplasmosis caused by Toxoplasma gondii.

Genera and species that cause coccidiosis:

Genus Isospora is the most common cause of intestinal coccidiosis in dogs and cats and is usually what is meant by coccidiosis. Species of Isospora are species specific, meaning they only infect one type of species, such as Isospora canis, Isospora ohioensis, Isospora burrowsi, and Isospora Neorivolta which infects dogs. Isospora felis and Isospora rivolta infect cats. The most common symptom is diarrhea.

Genus Cryptosporidium contains Cryptosporidium parvum and Cryptosporidium Muris infecting cattle and other mammals including humans. Cryptosporidium hominis is specific for immunocompromised individuals, such as humans, dogs and cats.

Genus Hammondia does not cause disease. It is transmitted by ingestion of cysts found in the tissue of grazing animals and rodents. Hammondia heydorni infecting dogs. Hammondia hammondi and Hammondia pardalis infecting cats.

Genus Sarcocystis infect carnivores such as dogs and cats that ingest cysts from various intermediate hosts.

Genus Toxoplasma has one important species, Toxoplasma gondii. Cats are the definitive host but all mammals and some fish, reptiles, and amphibians can be intermediate hosts. Only cat feces will hold infective oocysts but infection through ingestion of cysts can occur with the tissue of any intermediate host.


Eimeria Transcript Database

The assembled transcripts of the three Eimeria species Eimeria acervulina, Eimeria maxima and Eimeria tenellaare are published in the the Eimeria Transcript Database (EimeriaTDB).

The Eimeria Transcript Database (EimeriaTDB) is an integrated resource of cDNA sequencing and annotation data of Eimeria spp. of domestic fowl. EimeriaTDB is maintained by the Coccidia Molecular Biology Research Group at the Institute of Biomedical Sciences, University of São Paulo, Brazil. [15]

Parasites of the genus Eimeria infect a wide range of vertebrate hosts, including chickens. The Eimeria Transcript Database contains the transcriptomes of Eimeria acervulina, Eimeria maxima and Eimeria tenella, All cDNA reads have been assembled, and the reconstructed transcripts. The main goal is to offer a public repository of sequence and functional annotation data of reconstructed transcripts of parasites of the genus Eimeria. [16]

New Zealand native passerines are hosts to a large variety of gastrointestinal parasites, including coccidia. Schoener et al. 2013 found a prevalence of coccidian infection in the New Zealand bird species up to 38 %, primary of the family Eimeriidae. [17]

The prevalence of coccidia infection in goats were found by Balicka-Ramisz et al. 2012 to be up to 100% in Poland and Ukraine. Nine Eimeria spp. were identified in feces samples in Western Pomerania and Lviv regions: E. arloingi, E. chrisienseni, E. jolchijevi, E. ninakohlyakimovae, E. alijevi, E. capina, E. caprovina, E. hirci, E. apsheronica. The prevalence of infection in Western Pomerania of adult goats was 74% and 100% in kids. The results of the present investigation have implications for the control of coccidial infections in goats in Europe. [18]

Toxoplasmosis and Neosporosis in beef cattle in Thailand

Wiengcharoen et al. 2012 report that beef cattle in Thailand had a greater exposure to Toxoplasma gondii than Neospora caninum, and they should be regarded as a potential source of Toxoplasma gondii infection to humans. According to the authors neosporosis, despite low prevalence, is still a risk for morbidity among cattle, including abortions in Thailand. [19]


Moisture and temperature influences Coccidiosis in poultry [20]

Coccidiosis is one of the most prevalent diseases in poultry. Abd El-Wahab et al. report that floor heating with exposure to wet litter increased the Eimeria adenoeides oocyst count in the excreta of secondary infected birds compared with poults which were not exposed to wet litter. Floor heating decreased foot pad dermatitis scores compared with groups in housings without floor heating. The authors stress that the process of sporulation is affected by moisture and temperature of the litter.


Diagnostic marker for cattle neosporosis [21]

Neospora caninum infects domestic and wild canids as well as many warm-blooded animals. He et al. 2013 present a specific diagnostic assay using the N. caninum 40-kD surface antigen (p40), similar to NcSAG1 and NcSRS2. The authors writ that the assay is an excellent marker for the diagnosis of neosporosis in cattle.

Giardia and Cryptosporidium

Giardia and Cryptosporidium are common enteric parasites of domestic animals, particularly dogs, cats and livestock. The epidemiology of infections was recently cleared using molecular epidemiological. [22]

These data support the hypothesis that Cryptosporidium hominis is spread only between humans. However domestic livestock, predominantly cattle is reservoir for Cryptosporidium parvum. Transmission takes place by direct contact with infected cattle but also indirectly through drinking water. Giardia duodenalis zoonotic transmission is not considered as a major risk for human infections. [23]

Cryptosporidium has become the most important contaminant found in drinking water, and 12 waterborne outbreaks in North America since 1985 with a mortality rate in the immunocompromised the ranged from 52% to 68%. The immunofluorescence antibody assay (IFA) using epifluorescence microscopy has been used to examine the occurrence of Cryptosporidium in sewage. [24]

O'Handley and Olson 2009 describe the effects of giardiasis and cryptosporidiosis in ruminats. The authors report that Giardia duodenalis infections are acquired during the first few months of life, tend to be chronic, and may be a production-limiting disease of ruminants. Cryptosporidia parvum infections causes diarrhoea in neonatal ruminants and Cryptosporidia andersoni, is seen as an emerging disease of cattle. [25]

Giardia and Cryptosporidium spp agents of waterborne diseases [26]

Brandonisio 2006 stresses that Giardia and Cryptosporidium spp. are parasitic protozoa which are frequent etiologic agents of waterborne diseases, particularly in Italy The author reviews current methods for evaluating the presence of Giardia cysts and Cryptosporidium oocysts in water and new methods for cyst/oocyst removal from drinking water and wastewater.

The resistant stages produced by Cryptosporidium and Giardia (oocysts and cysts, respectively) are remarkably stable, and can survive for weeks to months in the environment. The infective dose is low, even a single oocyst or cyst may cause an infection. Most faeces that contain (oo)cysts end up in the environment and can be spread to foods by irrigation or by direct contact, and can persist in the water, as routine treatments eliminate only a fraction of these stages. [27]

Smith and Nichols 2006 refer to the reasons why outbreaks of water- and foodborne diseases caused by Cryptosporidium, Giardia and Toxoplasma are successful. They are pathogen for many hosts including man and have a low infectious dose their infectious stages are small and resistant to the linking media, and they resistant to usual water disinfectants. The authors also refers to infection of humans by the microsporidia, Balantidium and Blastocystis being transported by food and water. [28]

Fayer, Dubey and Lindsay 2004 drawed attention upon Giardia, Cryptosporidium, Toxoplasma and the worldwide pollution of coastal marine environment when great amounts of feces from humans, their pets, and their domesticated animals enter estuaries and coastal waters. The authors stress that sewage carries encysted zoonotic protozoan parasites contaminating bathing beaches, are filtered and concentrated by shellfish eaten by humans and marine mammals, and infect a wide range of marine animal hosts. [29]

Appelbee and colleagues looked at the diversity of free-living and captive terrestrial and marine mammalian wildlife species infected with Giardia and Cryptosporidium. The authors highlight the importance of environmental pollution with human and domestic-animal fecal material as a pathway for wildlife infections with protozoan parasites such as Giardia and Cryptosporidium. Molecular-genotyping techniques offer deeper insights to host specificity and possible transmission routes of these parasites. [30]

Methods for the diagnosis of Cryptosporidium and Giardia [27]

Caccion 2004 highlights the necessity of the accurate identification of a parasite at the species and/or genotype level in human and veterinary parasitology, including the diagnosis, the taxonomy, the treatment and the control. Giardia and cryptosporidium, despite differing in biology, share a complex series of transmission routes turning molecular assays very useful to clarifie their epidemiology.

The author stresses that PCR does not provide information on the viability and infectivity of the pathogen. These informations may be obtained using indirect methods, such as inclusion/exclusion assays using vital dyes or the Reverse-Transcriptase PCR (RT-PCR) RT which usually targets the heat shock protein (hsp) 70 gene. Heat shock proteins hsps are efficiently formed by stressed organisms, such as (oo)cysts exposed to a thermal shock. The hsps wehich are formed under such conditions increase the detection sensitivity and are an index of viability of the cysts.

The real-time PCR allows the continuous monitoring of amplicon which are pieces of DNA formed during the amplification reaction, quantitative aspect of the infection could be studied with exquisite sensitivity.

Molecular characterization of Giardia duodenalis and Cryptosporidium spp [31]

A high prevalence of G. duodenalis of 42.0%, Cryptosporidium parvum 21.7% and Cryptosporidium bovis 1,4% was found by Coklin and colleagues 2007 in Canadian cattle in Ontario. Mainly calves were affected. Molecular characterization of the genotypes confirmed a frequent infestation of humans by these parasites.

Methodology used by the authors

Following DNA extractions from faecal samples, nested-PCR protocols were used to amplify fragments of the 16S rRNA gene andthe heat-shock protein 70 (HSP-70) gene for determining the prevalence of G. duodenalis and Cryptosporidium spp. infections, respectively. Genotypes of G. duodenalis, and species of Cryptosporidium, were determined by means of DNA sequencing of amplicons, and subsequent sequence alignment.

The authors concluded that there risk of transmission of Giardia duodenalis and Cryptosporidium parvum between cattle and humans by contaminated water or food, or direct faecal-oral transmission.

In 2009 Coklin and colleagues found 6.2% infections of Cryptosporidium parvum in dairy calves in Prince Edward Island, Canada. The authors stress the potential risk of zoonotic transmission between dairy calves and humans in this region.The presence of oocysts in the fecal samples was determined , using immunofluorescence microscopy. Molecular characterization was done using a nested-PCR protocol to amplify fragments of the Cryptosporidium heat-shock protein 70 gene, followed by DNA sequencing. [32]

New sub-genotype of Cryptosporidium parvum [33]

In cattle from the Qazvin province , Iran 72.6% of the positive samples as Cryptosporidium parvum, 17.7% as Cryptosporidium andersoni, 7.8% as Cryptosporidium bovis were found by Keshavarz and colleagues. The authors report the finding of a novel genotype of C. parvum possessing a single mutation on MboII restriction. This new sub-genotype represented 1.9% of the analysed samples. The authors used microscopic characterization and ocysts were analyzed using PCR assay of 18S SSU rRNA, restriction fragment length polymorphism (RFLP) and sequencing.

In Teheran Pirestani and colleagues 2007 found a zoonotic or 2 genotype (C. parvum) in isolates from bovine samples. In human samples anthroponotic or 1 (C. hominis) and zoonotic genotype or 2 (C. parvum) were found. Ooicysts were isolated and genotyped by means of a Nested-polymerase chain reaction/restriction fragment length polymorphism analysis of the 18s rRNA gene. [34]

Eastwood and colleagues 2008 identified two subgenotypes of Cryptosporidium hominis and four subgenotypes of Cryptosporidium parvum species from humans from farms in New South Wales. All four of the C. parvum subtypes found in humans were also found in the cattle. This suggests that zoonotic transmission is an important factor of Cryptosporidium transmission in rural regions. PCR sequence analysis of the 18S rRNA was used to determine species/genotype and subgenotype by sequence analysis of the GP60 gene. [35]

Geurden and colleagues 2009 report that Cryptosporidium and Giardia are frequently found in the stool of domestic ruminants, especially young animals. The authors assessed the occurrence of these protozoan in captive wild ruminats at the Antwerp Zoo (Belgium) where 8.9% for Giardia duodenalis assemblage A and American bison (Bison bison) calves on a commercial breeding farm and 23.2% for Giardia duodenalis assemblage A and E.

Cryptosporidium-positive cases were 7.5% in the Antwerp Zoo animals and 3.7% in the Bisons from the breeding farm. The authors concluded that captive wild ruminants can serve as reservoir Cryptosporidium and Giardia. Detailed methodology is described by the authors. [36]

Solar UV inactivates Cryptosporidium oocysts [37]

King and colleagues 2008 found that natural sunlight inactivated up to 90% of Cryptosporidium parvum oocysts in drinking water and environmental waters within the first hour. The solar ultraviolet UV-B wawelength had the highest germicidal effect, whereas dissolved organic material decreased the effect of solar light.

Water treatments to control Cryptosporidium and Giardia [38]

Betancourt and Rose 2004 report that Cryptosporidium parvum oocysts are particularly more resistant than Giardia lamblia cysts to removal and inactivation by conventional water treatment (coagulation, sedimentation, filtration and chlorine disinfection). Success of conventional treatment depends on the effectiveness of coagulation pretreatment and properly functioning conventional filters. Additional disinfection procedures, such as chlorination, chlorine dioxide, ozonation and ultra violet [UV] irradiation) disinfection procedures by chemical or physical methods are required.

The effectiveness of inactivation of protozoan parasites in food, water and environment [39]

According to Erickson and Ortega 2006 treatments used to inactivate protozoan parasites (Giardia, Cryptosporidium, and Cyclospora) in food, water, and environmental systems include freezing, heating, filtration, sedimentation, UV light, irradiation, high pressure, and ultrasound. The authors stress that ozone is a more effective than chlorine or chlorine dioxide. However, one should have in mind that synergistic effects of sequential inactivation treatments of conventional systems may increase their efficiency.

Effect of temperature on the die-off rate for Cryptosporidium parvum oocysts in water, soils, and faeces [40]

Oocysts survival in water: Cryptosporidium parvum oocysts are inactivated when exposed to a temperature of 72.4° for 1 min or 64.2° for more than 2 min. The lowest die-off rate was found at 4°. Freezingt is predicted to inactivate 99.99% of oocysts in 853 days at -4° or 64 days at -22°.

The die-off rate for oocysts in river water at 5° is similar to that in autoclaved river water, but at 15°, oocyst die-off occurs more rapidly in natural than in autoclaved river water. The difference is perhaps due to increased biological or biochemical activity at 15°.

Oocysts survival in soil

Desiccation is probably lethal to oocysts. Reports say that decreasing the soil water potential by adjusting NaCl solution linearly increases the rate of population degradation.

Oocysts survival in faecis

Temperature is a key factor influencing oocyst survival in feces. A strong exponential relationship between the die-off rate and the temperature was found, being stronger in faeces than in water. The viability of oocysts excreted by calves in solar housing did no differ from those in conventional housing.

Cryptosporidium, a major cause of diarrhoeal disease

Cryptosporidium and Giardia are the most common cause of protozoal diarrhea worldwide. One to ten Cryptosporidiumm oocysts or Giardia cysts are sufficient to get sick. Cryptosporidium oocysts and Giardia cysts can resist to different physical and chemical treatments. In water, they can persist in different forms a few months. Contamination of foods occur by unhygienic food handling or by the environment. Cryptosporidium oocysts and Giardia cysts can survive to different food process.

Cryptosporidium and Giardia present anthroponotic, zoonotic transmission, waterborne and foodborne transmission. The oocysts and cysts can survive for weeks to months in the environment. Faeces that contain oocysts or cysts may be spread to foods by irrigation or by direct contact. Routine treatments of drinking water eliminate only a fraction of these stages.

The detection by immunofluorescence methods like ELISA or by microscopy method are not recommended due to genetic diversity, lack of sensitivity and subjectivity of the analyse. Molecular techniques (real time RT-PCR) are the methods of choice for Cryptosporidium and Giardia detection after DNA extraction and purification from the sample, and special commercial kits were developed. [41]

Molecular tools improving detection and understanding of Cryptosporidium infections [42]

A review conducted by Xiao 2009 highlights molecular tools detecting and differentiating Cryptosporidium at the species/genotype and subtype levels in humans and animals. These molecular epidemic studies show the importance of Cryptosporidium infections and improves the understanding of their sources. The author stresses the importance of genotyping and subtyping tools to improve the understanding of the epidemiology of cryptosporidiosis.

Understanding of the different metabolic pathways of Plasmodium and Cryptosporidium [43]

According to Mogi and Kita 20101 the Apicomplexans, obligate intracellular parasites, have undergone a reductive evolution like the Plasmodium, which in the blood stages of mammalian hosts, has its mitochondrial enzymes down-regulated and its energy metabolism relies mainly on glycolysis. Mitosomes of Cryptosporidium parvum and Cryptosporidium hominis (in humans) lack mtDNA and other metabolic pathways, which are still present in mitosomes of Cryptosporidium muris (in rodents). The authors write further that Cryptosporidium and Perkinsus use pyruvate-NADP(+) oxidoreductase (PNO), malate-quinone oxidoreductase(MQO), and alternative oxidase (AOX). All apicomplexan parasites and dinoflagellates share MQO. The authors hope that understanding mitochondrial metabolic pathways of Plasmodium, Cryptosporidium and Perkinsus will help the development of new chemotherapeutics

Detection of mutations in the 60 kDa glycoprotein gene (gp60) of Cryptosporidium [44]

Pangansa and colleagues 2010 assessed the effectiveness of a PCR-based restriction endonuclease fingerprinting (REF) method for the detection of mutations in the 60 kDa glycoprotein gene (gp60) of Cryptosporidium. This gene displays substantial intraspecific variability in sequence, particularly in a TCA microsatellite region, and is used as a marker in molecular epidemiological studies of Cryptosporidium hominis and Cryptosporidium parvum. REF is useful to detect the nucleotide variability in the gp60 gene within each of the two species. The authors highlight the high-throughput potential and relatively low-cost of REF for genetic analyses of C. hominis and C. parvum, and to identifying sources of infection. REF may also be useful to study other protozoan and metazoan parasites.

Cryptosporidium, the the major cause of dysentery [45]

According to Jex and Gasser 2010 the prevention of cryptosporidiosis in humans should focus on prevention and control strategies and epidemiology using the 60-kDa glycoprotein gene (gp60) as genetic marker for Cryptosporidium infections. The authors provide a global analysis which reveals a low diversity of Cryptosporidium, however, there is a limited knowledge about the genetics of cryptosporidiosis in developing nations in Africa and Asia, and about many animals infection sources. The authors call for comparative genome sequence surveys based on gp60 data to improve intervention strategies against cryptosporidiosis.

Importance of specific methods to detect diarrhoea agents among tourists [46]

Agnamey and colleagues 2010 report diarrhoea among tourists returning from West Africa due to Cryptosporidium hominis and Isospora belli. The authors stress the importance of the detection of coccidiosis in diarrhoeic travellers with the use of specific methods.

New Cryptosporidium parvum subgenotype IIn in Indian children [47]

Analysing diarrhoeal stools from hospitalized Indian children aged under 5 years Agnamey and colleagues 2010 found that 2.7% were positive for Cryptosporidium. Microscopy, PCR-RFLP and/or sequencing at the SSU rRNA and Cpgp40/15 loci for species determination and subgenotyping were used. Cryptosporidium hominis was the most frequent genus and subgenotypes Ie, Ia, Ib and Id was spread over all places. The authors report a novel Cryptosporidium parvum subgenotype, IIn. The rate of cryptosporidiosis was reported to increase during hotter and drier weather.

Norway sheep are reservoir of zoonotic Cryptosporidium [48]

Robertson and colleagues 2010 assessed cryptosoridiosis and giardiasis of Norwegian lamb farms using immunofluorescent antibody test detecting Cryptosporidium oocysts and Giardia cysts. Findings of Giardia were 31% and 24% for Cryptosporidium. PCR analysis targeted glutamate dehydrogenase and beta-giardin genes for Giardia, and SSU rRNA and actin genes for Cryptosporidium. Only one isolate of Giardia was Assemblage B (zoonotic), but 35 isolates of Cryptosporidium were cervine genotype (potentially zoonotic). The authors concluded that sheep in Norway are a reservoir of zoonotic Cryptosporidium, but Giardia are of no concern.

Genotypes of Cryptosporidium parvum from calves and sheep in Spain [49]

In Galicia, Spain 49.2% of diarrhoeic calves and 30.7% lambs were tested positive for Cryptosporidium by microscopy and molecular tests. Cryptosporydium parvum from calves belonged to the subtype IiaA15G2R1, and one was of the novel subtype IIaA13G1R1. In sheep the subtipes IiaA16G3R1 and IIaA15G2R1suggest a limited genetic diversity in calves. The authors stress that calves and lambs should be considered as zoonotic reservoirs.

Seasonal variation of the genetic morfology of Cryptosporidium with implication on parasite control in preweaned cattle [50]

Szonyi and colleagues 2010 report that 5% Cryptosporidium parvum-like species and 1% Cryptosporidium andersoni were found using the flotation method. C. parvum-like species was found in 26% of the samples among preweaned calves in summer, compared with 11% in winter, and no oocysts of C. parvum-like in cattle older than 5 months were detected. The 18s rRNA gene revealed that in the summer, 42% of the C. parvum-like oocysts were zoonotic, compared with less than 74% during the rest of the year. Better understanding of management practices or ecological factors will improve the control of this parasite in preweaned calves say the authors.

Cattle may be a source of Cryptosporidium in Hungary [51]

Plutzer and Karanis 2007 determined the genotype and subtypes of Cryptosporidium from faecal samples from calves with diarrhoea in Hungary Genomic DNA was extracted and nested PCR amplified the partial SSU rRNA and GP60 genes digested by SspI, VspI and MboII restriction enzymes. Cryptosporidium parvum IiaA16G1R1 was found to be the most common subtype and two isolates were found to contain the C. parvum allele IId and a new Cryptosporidium parvum IIa A18G1R1 subgenotype. The authors concluded that cattle can be a source of cryptosporidial infections for humans and animals in Hungary.

Cryptosporidium detection method in water [52]

Nichols, Campbell and Smith 2007 presented a nested PCR-restriction fragment length polymorphism (RFLP) method for the detection Cryptosporidium spp. oocysts in natural mineral waters and drinking waters, detecteding less than 5 oocysts per sample.

Transmission of Cryptosporidium from cattle to man an dairy farms [53]

Khan and colleagues 2010 assessed the importance of animals as source of human Cryptosporidiosis in West Bengal, India. A total of 11.7% of the cattle were found positive for Cryptosporidium parvum, Cryptosporidium bovis, Cryptosporidium ryanae, Cryptosporidium andersoni and Cryptosporidium suis-like genotype. Infection of farm workers comprised Cryptosporidium hominis, C. parvum and a novel C. bovis genotype. The authors highlight the risk of Cryptosporidium transmission from cattle to humans on dairy farms.


Cryptosporidium parvum dominant infections in young calves in France [54]

A study by Follet et al. 2011 revealed the presence of Cryptosporidium parvum (43.8%), Cryptosporidium ryanae (28.5%), and Cryptosporidium bovis (27%) in stool samples of young calves. One animal was infected with Cryptosporidium ubiquitum.

The prevalence of species varied with the age of the animal. Cryptosporidium parvum caused 86.7% of Cryptosporidium infections in 5-week-old calves, but declined to 1.7% in 15-week-old animals. The authors extracted the DNAfrom the stool samples and the partial 18S-rDNA and 60 kDa glycoprotein genes of Cryptosporidium were amplified by nested PCR. Overall 70,4% of the calves were found positive for Cryptosporidium. The authors concluded that zoonotic Cryptosporidium parvum is the dominant species in young calves.

Cryptosporidium oocysts in paddock and forage [55]

According to Boyer and Kuczynska 2010 adult beef cattle shed oocysts into the environment. The oocysts of Cryptosporidium oocysts are often found in streams and groundwater in livestock agriculture areas. Mean annual oocyst prevalences on forage were 52.4% in pasture and hay paddocks 40.5%. Wild animals act as vector among paddocks. The authors suggest canopy management, short-cycle rotational grazing, and control of wildlife as strategies to reduce number of Cryptosporidium oocysts in pasture and protect water supplies.

Modified method for purifying Cryptosporidium oocysts [56]

Huang and colleagues 2010 describe a modification of the purification method of Cryptosporidium oocysts. They used Sheather's sucrose solution diluted with distilled water as an alternative to PBS. A high viability of the oocysts of more that 96% after 1 hour incubation in 37 degrees C were attained.

Parasitic contamination in wastewater and sludge samples in Tunisia [57]

According to Khouja and colleagues 2010 water scarcity compel to the reuse of wastewater or sludge in Tunisia. Wastewater guidelines specific limits for ova of helminths less than 1 egg/l. Protozoan parasite contamination is not specified. The authors assessed, therefore the Tunisian water treatment and found a high diversity of helminth and protozoa contamination of raw wastewater. Six of eight treated wastewater presented parasite contamination with helminths, Cryptosporidium, Giuardia and Entamoeba. Sludge samples presented parasites, Cryptosporidium and Giardia in high frequence from human and animal origin. The authors stress the importance to monitor wastewater and sludge concerning these pathogens.

Monitoring wastewater plants in China [58]

The removal of Cryptosporidium, Giardia, and microbial indicators, including somatic coliphages and faecal coliforms by treatment plants in Beijing, China presented reduction ratios of 0.12 log for Cryptosporidium and 0.18 log for Giardia by the primary treatment process. The authors note further that oxidation ditch process had higher reduction efficiency to Cryptosporidium and Giardia than anaerobic-anoxic-oxic process and conventional activated sludge process, due to longer retention time and higher concentration.

As tertiary treatment greater reduction of pathogens were attained using membrane ultrafiltration, compared with conventional flocculation sedimentation and sand filtration process, as the tertiary treatment.

Outbreaks of waterborne transmission of parasitic protozoa in humans [59]

Cryptosporidium is a protozoan that can cause gastro-intestinal illness with diarrhea in humans. Cryptosporidiosis is a zoonosis found in goats and sheep and pigs. Baldursson and Karanis 2011 report at least one hundred and ninety-nine outbreaks of waterborne transmission of parasitic protozoa between 2004 and 2010. Almost half of the outbreaks occurred in Australia, a third in North America and less than a fifth in Europe.

The most frequent parasitic infection was Cryptosporidium spp. With a frequency of 60.3% of all outbreaks, Giardia lamblia with 35.2% and other protozoa with 4.5%. Less frequent were outbreaks of Toxoplasma gondii, Cyclospora cayetanensis. Acanthamoeba spp. Giardia lamblia Cryptosporidiumparvum, Entamoeba histolytica and Blastocystishominis Countries at highest risk of such outbreaks lack surveillance systems.

Source of human infections of Cryptosporidium sp.

Fiuza et al. 2011 found 4,54% of samples of faeces of dairy cattle positive for Cryptospporidium andersoni at farms in the state of Rio de Janeiro, Brazil. Molecular analysis by polymerase chain reaction (nested PCR) of the 18S rRNA were used in this study. The authors stress that such infections may affect cattle productivity and represent a source for human infection. [60]

Fiuza et al. used nested polymerase chain reaction (PCR) to amplify an 830-bp fragment of the small subunit rDNA (SSU rRNA) gene and sequencing of all positive PCR samples. Cryptosporidium sp, pig genotype type II (PGII) was positive in 2.2% of the samples were positive and were identified as pig genotype type II (PGII). This genotype was found also found in cattle which had no contact with pigs and in humans. The authors call for more studies on possible human infections with Cryptosporidium from animal source. [61]

In Brazilian lambs 1,6% of samples of faeces were positive for Cryptosporidium ubiquitum using polymerase chain reaction (nested PCR) in two steps of the SSU rRNA. Cryptosporidium ubiquitum is considered a zoonotic pathogen, however, its local low frequency may not present a high risk to humans. [62]

Cryptosporidium in water samples in Brazil [63]

Araújo et al 2011 reports the detection of Cryptosporidium oocysts in 30% of water samples. Collected in the state of São Paulo, Brazil. Using nested-polymerase chain reaction 18S ribosomal RNA gene sequences Cryptosporidium hominis and Cryptosporidium sp. were identified in recreational water and Cryptosporidium. meleagridis in surface water samples.

The authors stress that the identification of Cryptosporidium is difficult because of the small size and morphology of the oocysts when the identification is being done by microscopy. Molecular methods are therefore suggested by the authors to study the epidemiology of Cryptosporidium. Cryptosporidium is which is one of the most important water contaminants, causing waterborne outbreaks of diarrhoeal diseases worldwide.

Giardia canis virus as genetic tool to alter Giardia canis [64]

Chen and colleagues 2006 described the cultivation of Giardia canis trophozoites infected with Giardia canis virus.

Chen and colleagues 2009 explain the structure of this virus and its effects on Giardia canis trophozoites being released to the media as mature infectious viral particles. The authors suggest that Giardia canis virus may be used for gene manipulation of Giardia canis. [65]

Sewage treatment [66]

Sewage sludge intended for arable land use needs to be rigorously assessed for quality due to the high content of metals (cadmium, arsenic, copper, lead, mercury, and zinc), persistent organic pollutants (the organochlorines aldrin, dieldrin, heptachlor, dichlorodiphenyltrichloroethane, and lindane), and pathogenic microorganisms (bacteria, viruses, protozoa, and helminths) to ensure no transmission of harmful elements to humans through entry into the food chain via crops or grazing animals. According to European Union regulations (EEC 1774/2002) [67], stabilized organic residues must be adequately treated and proven hygienically safe, prior to the application of sewage sludge to arable land.

Storage of Sewage

Storage of sewage sludge was applied as the sole treatment, with the aim of sanitization in terms of destroying pathogenic microorganisms, a method proven not effective and therefore discontinued. The most frequently used stabilization methods for sewage sludge are biological anaerobic and aerobic digestion. However, neither of these two procedures generates sludge that is better quality than class B grade, promoting a future shift to the use of alternative methods, such as alkaline stabilization and heat drying, to further reduce pathogen level resulting in class A sludge with fewer user restrictions. An additional promising option of producing hygienically safe material for arable recycling is to combine stabilization procedures, such as digestion, with pasteurization or liquid composting.

Chemical treatment

Lime stabilization (calcium hydroxide) to raise the pH to 12.0 for at least 2 hours. It is an interesting alternative to anaerobic and aerobic digestion.

Composting;

In composting, liquid sludge is treated with a bulking agent, such as wood chips, dry compost, or municipal refuse.

Pasteurization

Pasteurization of biowaste at 70° for at least 1 h is an effective approach to eliminate most pathogens.

Toxoplasma gondii [68]

Toxoplasma gondii is capable of infecting all warm-blooded animals including humans, such as congenitally infected children which presente hydrocephalus, retinochoroiditis and encephalitis. The parasites are associated with severe intraocular inflammation and was the major cause of abortion in sheep in New Zealand. The cat is a definitive host. The oocyst stage of Toxoplasma gondii is shed in the faeces of infected cats and acts as a source of infection for many intermediate hosts. It causes infection in herbivorous animals and people with vegetarian diet.

The life cycle of Toxoplasma gondii comprises the sexual stage (coccidia like) wich takes place only in domestic and wild cats, which makes these animals the parasite's primary host. The asexual part of the life cycle can take place in any warm-blooded animal, including birds.

Infection of humans occur ingesting oocysts on unwashed vegetables of improper cooked infected meat.Acute stage Toxoplasma infections can be asymptomatic, but often give flu-like symptoms in the early acute stages, and like flu can become, in very rare cases, fatal. The acute stage fades in a few days to months, leading to the latent stage. Latent infection is normally asymptomatic. If infection with T. gondii occurs for the first time during pregnancy, the parasite can cross the placenta, possibly leading to hydrocephalus or microcephaly, intracranial calcification, and chorioretinitis, with the possibility of spontaneous abortion (miscarriage) or intrauterine death. [69]

Reducing Toxoplasma infection risk [70]


Toxoplasma gondii infection from cat litter [71]

According to Dubey et al 2011, oocysts of Toxoplasma gondii remain infectious to people for 14 days in all types of commercial cat litters. The definitive host of Toxoplasma gondii is the cat, but the parasite can be carried by birds, rats, other warm- blooded animals and humans.

The parasite may cause serious or even fatal effects on a fetus during pregnancy. or on an immunocompromised humans are also seriously affected by the disease caused by Toxoplasma gondii. The infection infection may present flu-like symptoms in the early acute stages. The acute stage fades in a few days to months, leading to the latent stage. The authors recommend to change cat litter daily to avoid human infections with Toxoplasma gondii.

Vyas and Sapolsky 2010 report that Toxoplasma infections change the behaviour of rats and mice, making them drawn to, rather than fearful of, the scent of cats, but does not change any other fears, like the aversion to open spaces or of unfamiliar-smelling food. It is being suggested that the parasite causes the behavioural change to profit from the cycle in the cat. [72]

Studies have also shown behavioural changes in humans, such as slower reaction times, increased risk of traffic accidents, links to schizophrenia and reckless behaviour.

Toxoplasma gondii in Brazilian dairy cows and their foetuses [73]

Macedo et al. 2012 describe the serology and isolation of Toxoplasma gondii strains from blood and tissue of pregnant dairy cows and foetuses in Southern Brazil.

Antibodies against Toxoplasma gondii were observed in 48.3% of cows and 3.7% of fetuses. Bioassay found 23% of fetuses and 10.0% of cows as positive. Toxoplasma gondii type II strain was isolated from a blood sample of a cow and of a foetus. The authors stress that transplacental transmission of Toxoplasma gondii occurs in dairy cows.

Genetics may reduce impact of African trypanosomiasis in cattle [74]

Human African trypanosomiasis, or sleeping sickness is a parasitic disease of people and animals, caused by protozoa of the species Trypanosoma brucei and transmitted by the tsetse fly. The disease is endemic in some regions of sub-Saharan Africa.

According to the World Health Organization around 30,000 Africans a year get sleeping sickness mainly in sub-Saharan African nations and disease of cattle leads to annual losses of up to $5 billion.

Goodhead et al 2011 report the finding of two genes which may help cattle breeders to select animals more able to survive an infection of Trypanosoma congolense, such as the humpless West African breed which is less susceptible to the disease compared with the high susceptible humped breed. However, the resistant humpless cattle is smaller, produce less milk, and is less docile than the humped the humped breed.

Trypanosoma congolense is responsible for the disease nagana in cattle and other animals including sheep, pigs, goats, horses and camels, as well as laboratory mice. It is spread by tsetse flies.

Laboratory mice, infected by trypanosomes presented different survival time after infection is controlled by three genomic regions Tir1, Tir2 and Tir3 which contain over one thousand genes. In these regions two genes, Pram1 at Tir1 and Cd244 at Tir3, were found to reduce survival time, and Tir2 increased survival time after an infection. The Tir2 loci was absent in trypanosomiasis susceptible animals.

These findings may be useful for breeding programs to screen African cattle and find animals which are more resistant to the disease and combine them with traits of increased productivity and drought tolerance.

The genome sequence of the agent of trypanosomiasis [75]

Trypanosomiasis, also called "sleeping sickness", is common in Western and Central Africa. The symptoms include changes in personality, alteration of the biological clock, confusion, slurred speech, seizures, and difficulty walking and talking. The disease is caused by Trypanosoma parasites and is transmitted by the female tsetse fly. It affects the human central nervous system. Berriman and colleagues 2010 describe the genome sequence for the strain of Trypanosoma brucei gambiense which is the most common causer of the sleeping sickness.

The authors compared this genome with that of Trypanosoma brucei brucei (T. b. brucei 927), a non-human infecting parasite from bovine infections. The sequence of genes were identical in 98.2 per cent in both genomes, varying only on one locus. However, ability to infect humans cannot be explained simply by the addition or removal of a few genes. The authors postulate that single letter changes in the genome, differences in the number of copies of genes; changes in how the activity of genes is regulated may be the cause of the virulence of Trypanosoma brucei gambienses. The genome sequences may help to find new drugs to fight the disease.

The authors also described a group of VSG proteins which gather at the surface of the Trypanosoma, protecting the parasite from the immune system of the host. A catalogue of VSGs might also provide valuable informations for further immunologic studies.

Human genetic resistance against falciparum malariae

IL3 variant at the chromosomal region 5q31-33 is protectiv against falciparum malriae in Ghana [76]

Meyer et al. 2011 write that the IL3 genotypes are implicated in the pathophysiology of falciparum malaria. The authors stress that in the control of malaria parasites is linked to the interleukin 3 gene (IL3) SNP rs40401, the IL3 genotypes rs40401(CT) and the rs40401(TT) were found to exert a protective effect of 25% and 33%, respectively, against malaria attacks. These genes are located in the chromosomal region 5q31-33.

Two loci associated with severe falciparum malaria were identified by German and African cooperation [77]

Timmann et al 2012 used the Genome-wide association (GWA) technique to compare the blood of 1300 severely diseased Ghana children with blood of healthy children. The authors identified two loci associated with severe falciparum malaria in patients. The chromosome 1q32 within the ATP2B4 gene encoding the main calcium pump of erythrocytes, necessary for the growth of the parasite inside of the red blood cell was an important loci.

A polymorphism on chromosome 16q22.2, linked to a gene encoding the tight-junction protein MARVELD3 was the second loci which were found in diseased persons. The protein is expressed at this loci playing a role in microvascular damage caused by parasitized erythrocytes.

Other genetic variant implicated in protection against the malaria disease are known from studies related to the sickle-cell trait and blood group O. Our findings underline the potential of the GWA approach to provide candidates for the development of control measures against infectious diseases in humans.

The results of this study, and further use of GWA technique, may help to develop new drugs against malaria which tropical disease affecting primary underdeveloped countries, causing the death of 655 000 persons in 2010, mainly children in Africa, says the WHO.


Parasitic worms

Parasitic worms are described under helmiths , comprising three groups:


Nematodes

also called roundworms.


Trematodes

like the flukes.


Cestodes

which are the tapeworms.
Bacteria can multiply in the human body almost indefinitely. Worm parasites do not multiply in the human host, they usually need to pass through stages in the human host and then they have to undergo other stages in one or more animals, im soil or water.
Some persons may harbor only few worm parasites, the infestation remains subclinical and symptomless. However with repeated exposures a massive infestation takes place and illness comes up.


Roundworms: Ancylostoma duodenale and Necator americanus

The infestation with both worms are alike and no laboratory attempt is made to differentiate among them, reporting as larvae of ancylostomideans.

Capillaria philippinensis

C. philippinensis is a roundworm causing intestinal capillariasis which appeared first in the Philippines and subsequently in Thailand, Japan, Iran, Egypt, and Taiwan. Humans acquire the infection by eating small freshwater fish raw. It is considered a zoonotic disease of migratory fish-eating birds.The parasite multiplies, and symptoms of diarrhea, borborygmus, abdominal pain, and edema. Pictures and full article by J H Cross are available at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=358231 [78]

Angiostrongylus costaricensis

A.costaricensis Morera and Cespedes, 1971 is a parasitic nematode of wild rodents that may produce abdominal disease in humans, already reported from most countries in the Americas, from Mexico to Argentina. Molluscs are intermediate hosts and shed infective third stage larvae (L3) in their mucus secretions. One possible mode of infection is the ingestion of raw vegetables and unpeeled fruits containing small molluscs or their contaminated mucous secretions. MORERA suggested refrigeration of food as part of prophylaxis based on experiments demonstrating a deleterious effect of low temperatures on the viability of L3. [79]


Life cycle of ancylostomideans

The hookworms are a quarter to halve an inch long. They attache themselves to the wall of the small intestines. The females produce eggs which are carried by feces.
In warm moist soil the eggs develop within a day or two into a larval form which is capable to penetrate human skin between toes if no shoes are worn. It causes local itch.
The blood stream carries the larva to the lungs where it gets though the lung wall and reaches the bronchi, the trachea and being swallowed getting to stomach and intestines, where it settles growing to an adult male and a female form. After fertilization of the eggs a new cycle starts.

Infestation from contaminated food and water

The larvae can be ingested from food and water lead to an infestation without the skin-blood-lung-cycle.This way of infestation is less common but should not be neglected handling with food, specially imported vegetables and fruits being eaten without proper washing and cooking.
Each worm can suck 0,5 ml or more blood from its host per day. Few worms do not get noticed but when more then two hundred are present severe anemia and intoxication takes place causing the hookworm disease.
The use of shoes reduces the possibility of an infection by the larva through the skin of the foot.


Strongyloides stercoralis

The disease caused by Strogyloides stercoralis is similar to the hookworm disease. The eggs can develop to small larvae and are carried by feces. In soil the larvae can reinfect man in the same way hookworm do.
The use of shoes reduces the possibility of an infection by the larva through the skin of the foot.


Trichuris trichiura

Is also called whipworm because of its shape. The ova are discharged in great number in the feces. In the soil they need several days to develop to infective larvae. They enter through the mouth in contaminated food and water.


Ascaris lumbricoides

Is is the largest roundworm being up to 12 inches long.
The eggs deposited in feces develop in soil during several weeks to infective stage. When swallowed the larvae penetrate the intestinal wall and a similar cycle as known as Ancylostomideans. If a considerable number of larvae are ingested at one time high fever and pneumonitis are caused.
The vermifuge principle of santonica seeds is santonin which is used to expulse Ascaris lumbricoides
Image Ascaris Ascaris lumbricoides from infected humans.

Pig farms source of human infection with round worm [80]

Ascaris lumbricoides/suum mainly infect humans and pigs. Ascaris lumbricoides worms usually infect humans, mainly in regions with poor sanitation, where the environment is contaminated with human feces. However, pig farms are a risk of nearby population.

In industrialized countries, human ascariasis is uncommon and cases are generally believed to have been imported. However, Ascaris suum infection of pigs occurs worldwide; in the United Kingdom, 3.4%–6.5% of pigs at slaughter have evidence of infection Bendall et colleagues 2011 describe a total of 63 acariasis cases in Cornwall, in England, between 1995 to 2010. Higher infection rates were found at children aged <5 years and living near pig farms. All worms from humans in Cornwall had pig-like DNA sequences, suggesting pigs as a source.

The authors calls for more studies to confirm that pigs are the source. Modification of animal husbandry and faecal waste disposal will be necessary.

The genetic region ITS1 is not suitable for epidemiology of Ascaris from pigs says study [81]

The internal transcribed spacer 1 (ITS1) was suggested to investigate the epidemiology of Ascaris infecting pigs. Leles et al 2010 found that the value of Ascaris ITS1 as a molecular marker should be reconsidered, due to a high intra-individual variability of ITS1 genotypes/halotypes.

Analysing different samples of Ascaris eggs, the authors found two genotypes, G1 and G6, and 13 new haplotypes, G1 and G6, were found in all Brazilian samples. Only genotype G1 could be found as relationship between Brazilian ITS1 genotypes/haplotypes and studies of Ascaris in China, Bangladesh, Japan, United Kingdom, Australia, and Denmark,


Prevalence of intestinal parasites

Data concerning soil-transmitted helminth infections reported infections of the population of the southern United States and Appalachia for hookworm 19,6%, Trichuris trichiura 55,2%, Ascaris lumbricoides 49,4%, and Strongyloides stercoralis 3,8%) in the United States is poorly understood. Starr and Montgomery 2011, however, stress that these data lay 25 years back and call for new studies to determine ther actual status. [82]

A prevalence of intestinal parasites up to 97,8% among pupils in rural schools in Nigeria were reported by Damen et al. 2011. Most frequent parasite found was Ascaris lumbricoides 19,1% and less frequently found was Trichuris trichiura 3,5%. The authors stressed the high prevalence rate of intestinal parasites amon the Almajiris population of northeast ern Nigeria with increases the risk of intestinal obstruction. [83]

Alyousefi et al. 2011 report infection rates of Giardia duodenalis and Entamoeba histolytica/dispar ver 17% each, and Cryptosporidium 1%. Also detected were Ascaris lumbricoides 2.4%, Schistosoma mansoni 0.3%, Hymenolepis nana 1.4% and Enterobius vermicularis 0.4%. in Jemen. The high prevalence of Giardia and Entamoeba is linked to low personal hygiene because 95% of the studied cases take bath less than twice a week and/or have contact with animals. The authors suggest preventive measures which include good hygienic practices, good animal husbandry practices, heightened provision of educational health programs, health services in all governorates including rural areas, and improve access to water. [84]

In Mugla city, south-west of Turkey, about 11% of elementary school students were found to be infested by intestinal parasites, with Ascaris lumbricoides being most common. Ekinci et al 2011 criticizes the lack of a sewage system in the Mugla province and recommends health education and periodically parasite examinations to be administered to the students and their families. [85]


Manual of methods of the investigation of intestinal parasites [86]

A very useful manual of standard methods of the investigation of intestinal parasites was compiled by the Health Protection Agency and can be downloaded.


Enterobius vermicularis

It is also called pinworm or seat worm The female migrate through the anus and deposit thousands of ova on the skin of the perianal region. When these eggs are ingested they develop into larvae and adult worms in the intestine. Laboratory diagnosis is done by microscopic examination of anal swabs.

Image Enterobius


Trichinella spiralis

Is a common parasite of flesh eating animals. It causes thichinosis.Adult trichina worms are just barely visible to the naked eye. They live in the duodenum.The female worm penetrates the intestinal wall and deposits its larvae in the mucosa. The larvae are carried by blood to all parts of the body. In the striated muscle tissue these larvae can grow and be surrounded by capsules, calcified cysts. When these cysts are ingested by other animals or by men the material is digested and the larvae gets free. In the duodenum the larvae develop to mature worms. The cycle begins again.
Trichinella spiralis parasites many flesh eating animals like hogs. Eating raw meat or not sufficiently heated pork containing larvae. As many infections of hooks are not noted there is pork on market with larvae. Due to growing of the global market veterinary control is not always perfect. If undercooked food with larvae is eaten infestation of man can take place. To avoid trichinosis cook meat appropriately. Avoid contaminated meat be eaten by hogs.
As imported meat from unknown and sometimes dubious origin are coming on market the number of human trichinosis is increasing again.
As treatment is very difficult all care should be made to avoid ingestion of meat with living larvae of Trichinella spiralis by refusing any food with raw or not sufficiently heated meat, this includes also all kinds of unheated sausages.

Image spiralis


Flukes (Trematodes)

Flukes are uncommon in developed countries. However due to increased travels and adventure trips their importance is growing.
One divides the flukes according to the place where they live:
Blood flukes
Liver flukes and
Lung flukes


Blood flukes

There are three important blood flukes:Schistosoma haematobium, Schistosoma mansoni and Schistosoma japonicum.

Schistosoma mekongi [87]

Schistosomiasis is caused by a variety of flatworm species. The blood fluke Schistosoma mekongi is known as a cause oif schistosomiasis in the Mekong River basin in South-East Asia where a mass treatment program in the mid-1990s reduced the prevalence of the disease.

Attwood, Fatih and Upatham 2008 compared DNA sequences of Schistosoma mekongi from the Mekong river and its tributaries in Cambodia, Laos and Malaysia. The authors fopund that Schistosoma mekongi is not confined the lower Mekong River, but migrates northwards from Vietnam, towards Cambodia and Laos. Human population at risk of infection could be up to 10 times greater than previously estimated. The authors expect the disease to spread into Laos. Schistosoma mekongi is found affecting communities along the Mekong River in northern Cambodia and Laos causing severe intestinal and hepatosplenic disease with high mortality rates Control programmes with praziquantel and information and education campaigns, reduced the numbers of infection, but small foci still exist. According Muth and colleagues 2010 the snail intermediate host, Neotricula aperta, present in the Mekong River and tributaries, may migrate further on. The authors call therefore for guidelines for the control of Sachistosoma mekongi and bilateral efforts between Cambodia and Laos. [88]

Polymerase chain reaction (PCR) to avoid spread of the schistosomiasis to non-endemic areas [89]

Kato-Hayashi et al. 2010 developed polymerase chain reaction (PCR) primers specific for human schistosome species (479 bp, Schistosoma mansoni; 365 bp, S. haematobium; 614 bp, S. japonicum; 303 bp, S. mekongi). The authors could detect schistosome DNA in animals one day post infection. This increases the effectiveness of the diagnosis in face of increased importation of schistosomiasis to non-endemic regions by travellers, immigrants and foreign workers coming from endemic areas.

Schistosoma haematobium, a human parasite, and Schistosoma bovis from ruminants are known in Kenya to inhabit the same Bulinus snails, live in the same freshwater habitat, and have similar cercariae. Barber, Mkoji and Loker 2000 described the second internal transcribed spacer (ITS2) region of the ribosomal gene complex (rDNA) of Kenyan, allowing successful identification of a single S. haematobium cercaria. The method used by the authors may help epidemiological studies to determine whether snails are transmitting a human or an animal schistosome, or both. [90] Leshem et al 2009 report infection of twelve Israeli travellers infected by Schistosoma mekongi in southern Laos. This report includes also some cases which were infected in northern Laos. [91]

Decreasing efficacy of artesunate in treatment and prevention of schistosomiasis [92]

Artesunate has been extensively used to treat and prevent Schistosoma japonicum infections in China with a high efficacy. Hua et al. 2010 report that the sensitivity of the fluke to artesunate has decreased from 100% to 13,5% during the last 10 years. Identical resistance to the medication have been found in Schistosoma mekongi and Schistosoma mansoni.

Mathematical models of Schistosoma transmission [93]

Ishikawa H, Ohmae reviewed epidemiology and environmental factors related to Schistosoma japonicum and Schistosoma mekongi infections. The authors focused on recent advances in mathematical models of Schistosoma transmission, stressing the usefulness of such models to predict the effects of control measures on suppression of the disease.


Schistosoma haematobium

Is found as chronic disease in Africa and in Asia.
The female gets her way to the capillaries of the lower intestinal or bladder wall where she discharges the ova which passes the wall of intestine or bladder to reach excreta causing inflammatory reactions which can turn out to malignant tumors.
Inflammatory reactions on the portal vessels to the liver are also known. The ova in the excreta can only develop when they get into water. There small free swimming larvae are formed. These larvae penetrate certain snails where three stages of development are passed. The last stage emerges from the snail and swims in the water until it comes in contact with human skin penetrating it and entering the blood stream.
Avoid to take bath in swallow water with low stream velocity. Hygienic condition of drinking and water used in the preparation of food in these areas in endemic areas should be looked upon.


Schistosoma mansoni

Causes endemic infections of man in the Caribbeans and the northern part of South America.
The adult worms are much narrower and more elongated than other flukes.


Schistosoma japonicum


Fasciola hepatica [94]

Human infections with Fasciola hepatica are seldom. Generally they are single cases,and rarely epidemic, However, the number of infections are rising being endemic in Bolivia.Adult parasites settle in hepatic biliary ducts. The main source of infection are salads of wild growing water plants like water cress and dandelion. Infection is frequent in cattle and goats.

Fasciola hepatica screening of milk cattle [95]

Sandra Koch says that the used »f2« antigen detecting ELISA presents a suitable screening method for the diagnosis on herd level and large scale surveillance programs of Fasciola hepatica and is to perform automatically from easily obtained bulk tank milk samples. On a screening of milk herd Koch found an overall prevalence of 32.2% infestation with Fasciola hepatica in Bavaria.
A remarkable high prevalence of 95% was found in the rural district Wunsiedel im Fichtelgebirge (Oberfranken). Because of the river systems in the Fichtelgebirge there exist a lot of wetlands and flood plains.

Fishborn flukes

The widspread fishborn flukes are Clonorchis sinensis, Opisthorchis viverrini and Opisthorchis felineus.
Human infection takes place when raw, slightly salted and frozen fish is eaten.

Clonorchis sinensis

The Clonorchis sinensis is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. This parasite lives in the liver of humans, and is found mainly in the common bile duct and gall bladder, feeding on bile. These animals, which are believed to be the third most prevalent worm parasite in the world, are endemic to Japan, China, Taiwan, and Sotheast Asia, currently infecting an estimated 30,000,000 humans.

The metacercariae can then be ingested by humans who eat undercooked or raw fish, who in turn become infected at the same time. These metacercariae enterthe small intestine and migrate into, and mature in the human liver, inside of the common bile duct and gall bladder.

C.H.Kim observed the prevalence of intestinal parasites and Clonorchis sinensis infection in the upper stream of Kumgang (River)in 1991 using cellophane thick smear and formalin-ether concentration technique. The parasite positive rate including helminth eggs and protozoan cysts was 40.8%, the paarasite positive rates for Clonorchis sinensis was 30.8%, Metagonimus spp. 14.5%, Taenia spp. 1.5%,while the rest of all other parasites summed only 4.6%. The authors concluded that the soil transmitted intestinal parasites including helminths eggs and protozoan cysts have been decreased remarkably among the inhabitants along the upper stream of Taechong Dam, Kum-gang (River), but Clonorchis sinensis, Metagonimus spp. and Taenia spp. are still morderate prevalent. [96]

Despite a gradual decrease in prevalence, clonorchiasis is still prevalent in East Asia. A large and compelling body of evidence links clonorchiasis and cholangiocarcinoma, although the mechanisms involved are not completely understood. Clonorchiasis induces biliary epithelial hyperplasia and metaplasia, and this could facilitate at least one stage of the carcinogenesis. [97]

Fishborne intestinal parasites are a risk for raw fish eating community [98]

According to Do Trung Dung and colleagues metacercarial stage of fishborne zoonotic trematodes were found in wild and farmed fishes. Fecal survey of a community that eats raw fish showed 64,9% of infected persons. with liver trematode Clonorchis sinensis recovered from 51.5%. The most numerous intestinal species of the family Heterophyidae were Haplorchis spp. (Haplorchis pumilio. H. taichui. H. yokogawai) (90.4% of all worms recovered).

The authors conclude that fishborne intestinal parasites are an unrecognized food safety risk in a country whose people have a strong tradition of eating raw fish.

Opisthorchis viverrini

Opisthorchis viverrini is a food borne trematode, important because of the sheer numbers of people infected and its serious morbidities such as hepatobiliary diseases and cholangiocarcinoma. It is found in Asia. Thailand have the highest number of infections. [99]

Opisthorchis felineus

It is widely spread in russia and is sometimes called Siberian liver fluke. Infection by undercooked fish eating.
The cat liver fluke is especially common in Siberia and the Ukraine, where up to 80% of the population is infected. Although these regions being the main endemic areas, it can also be found in Europe, Asia and North America. Domestic animals, especially cats, become infected by eating insufficiently cooked fish. Clinical signs are variable, and infestation with a moderate number of parasites is usually asymptomatic, however with a high quantity of parasites it may lead to hepatic insufficiency. This parasitosis is relevant to ichthyophagous animals (dogs, cats, pigs, foxes, wolverine, martens, beavers, otters, European pole cats, Siberian weasels, sables, Norway rats, water vole, rabbits, seals and lions) (Mehlhorn et al., 1992; Kelly, 1993; Mas-Coma et al., 2000; Cullen and Maclachlan, 2001). [100]


Intestinal flukes


Fasciolopsis buski

The fluke Fasciolopsis lives in the upper part of the small intestine. It contains both mail and female reproductive systems causing diarrhea and anemia.
The ova in faecis develop to larvae and penetrate certain types of snails as intermediate host. Leaving the snail the larvae becomes encysted on plants like nuts of the red ling or water chestnut which are eaten by man.
Here again the hygienic condition of water is important in the areas where trematodes may be found. Cooking of all foods, sanitary disposal of sewage and the elimination of snail hosts. This is not always possible due to high costs.


Echinostoma spp.[101]

They are intestinal flukes which are common in South-East AsiaThere are about 15 species of Echinostoma from which the most common is Echinostoma ilocanum The infections are acquired by eating raw or undercooked freshwater snails,clams, and fish containing the metacercariae. Pila luzonica is eaten uncooked by some people in the Philippines, and metacercariae from these snails developed into adults in a number of laboratory animals. Rats, mice and hamsters were the most susceptible. There seems to be little disease in humans and animals infected with Echinostoma ilocanum.

Tapeworms

Tapeworms are Cestodes with five important species:
Taenia solium
Taenia saginata
Diphyllobotrium latum
Hymenolepsis nana
Echinococcus granulosus


Taenia solium

Is the tapeworm of pork. The ova leave the body with the faecis free or in the interior of proglotides.
When these ova or proglotides are ingested by animals the larvae develop in the intestine, penetrate the wall and are carried by the blood to the muscles where they become bladder worms or cysticerci.
When the muscles are eaten the cyst wall is digested. The tapeworm the head of the worm adheres to the wall of the intestines and proglotides start to grow.

Neurocysticercosis caused by tapeworm Taenia solium [102]

Cysticercosis, a human infestation by Taenia solium is endemic in many resource-limited countries. In developed countries it is mostly encountered among immigrant populations. Leshem et al 2011 diagnosed between 1994 and 2009 nine cases of neurocysticercosis in Israeli travellers to South and/or Southeast Asia. Onset of symptoms, such as seizure, were reported to be 3.2 varying by 1.8 years after infection. [103]

Cysticerci can develop in any voluntary muscle in humans. In most cases, it is asymptomatic since the cysticerci die and become calcified. The cysticerci may also be found in the eye, causing visual difficulties or a visual loss. Subcutaneous cysts are nodules occurring mainly on the trunk and extremities. Neurocysticercosis generally refers to cysts in the brain. It presents seizures and, less commonly, headaches.

Neurocysticercosis is a parasitic infection of the central nervous system caused by Taenia solium larval cysts. It is the most common helminthic infection of the central nervous system and a leading cause of acquired epilepsy in Latin America, Southeast Asia, and central Africa. O'Neal et al 2011 determined the incidence of NCC and screened household contacts for tapeworms in Oregon during 2006 - 2009. They screened available data and collected faecal and blood samples from household contacts of recent case-patients.

The authors report an annual incidence of 0.5 cases per 100,000 general population and 5.8 cases per 100,000 Hispanics. In 22 households, 2 additional NCC case-patients but no current adult intestinal tapeworm infections were identified. The authors concluded that neurocysticercosis is of clinical and public health concern in Oregon, particularly among Hispanics, and suggest that public health intervention should focus on family members to identify additional case-patients.

Cysticercosis is acquired through faecal-oral transmission of tapeworm eggs shed in the faeces of a human carrying intestinal tapeworms. Ingested eggs release oncospheres, which invade the intestinal mucosa and disseminate throughout the body to form larval cysts. NCC occurs when cysts develop in the central nervous system and is the primary source of illness and death. The tapeworm's complete life cycle occurs in regions with poor sanitary infrastructure, where foraging pigs have access to human faeces.

Improved screening methods have been developed in the interim, including an ELISA for Taenia sp. coproantigens in faeces and an enzyme-linked immunoelectrotransfer blot (EITB) for serum antibodies against Taenia solium tapeworm. Serologic methods are desirable because they are specific to Taenia solium intestinal infection and highly sensitive (99%) and avoid the collection and processing of potentially infectious faeces.

Laboratory Methods used for this study

Fecal samples can be examined by light microscopy for Taenia spp. eggs or proglottids and by ELISA for Taenia spp. coproantigens. Serum samples were analyzed by EITB for antibodies against Taenia solium cysts (EITB lentil lection–bound glycoprotein) and against Taenia solium adult tapeworms (recombinant EITB). The rEITB for taeniasis is based on baculovirus expression-purified recombinant antigen rES33.

Detection assays using recombinant and synthetic antigens originating from the lentil lectin-purified glycoproteins (LLGPs) of Taenia solium cysticerci were developed by Lee and colleagues 2011 in a QuickELISATM format. for detecting cases with multiple, viable cysts. T24H QuickELISATM presented sensitivity and specificity values comparable to those of the LLGP enzyme-linked immunosorbent blot to detect cases of viable cysts. [104]

The recombinant EITB method for diagnosis of Taenia solium taeniasis [105]

Levine et al 2007 describe two serological taeniasis diagnostic tests using recombinant antigens rES33 and rES38 expressed by baculovirus in insect cells in an EITB format. Independent field testing in Peru showed 97% of the taeniasis sera were positive with rES33, and 98% of taeniasis sera were positive with rES38. rES33 and rES38 tests offer sensitive and specific diagnosis of taeniasis and simple to perform.

PCR test to detect Taenia solium muscle infection [106]

Polymerase chain reaction (PCR) test was employed to detect Taenia solium DNA in muscle lesions by Sreedevi et al 2011. TBR primers was targeted against the large subunit rRNA gene. Cox1 primers was targeted against cytochrome c oxidase subunit 1 gene of T. solium. The authors concluded that both PCR tests are efficient tools for validation of meat inspection results and rule out doubts in porcine cysticercosis.


Taenia saginata

Is the tapeworm of beef.
The adults are 6 to 20 feet long. The proglottids contain male and female reproductive organs.
The ova leave the body with the feces and are ingested from contaminated soil by the intermediate host like cattle. The larvae develop in the intestine, penetrate the wall and are carried by the blood stream to the skeletal muscles becoming bladder worms or cysticerci being spherical an inverted scolex.
When beef containing these cysts are undercooked eaten the cyst wall is digested and the scolex may attache to the intestinal wall and the proglotids develop to form the adult parasites.
If ova of Taenia saginata are ingested by men the same cycle observed in cattle take place. The larvae migrate through the body and cyst formation in various organs may take place. To control spreading of Taenia saginata it is important to avoid cattle to get in contact with human feces contaminated soil. Don't eat raw or undercooked meat as they may contain cysts of Taenia. Don't drink water from suspected areas without boiling as they may contain ova of Taenia.

Image Taenia


Diphyllobotrium latum

Diphyllobotrium latum is the fish tapeworm causing the broad tapeworm infection. The proglotids are much broader then long. Definitive hosts are man, cats, and bears.
In water the ova develop to ciliated embryos which must be ingested by a copepod where they develop during 2 to 3 weeks. If the copepod is swallowed by a fish the parasite develops in the muscle tissue of the fish. If the contaminated fish is eaten by men, cat or bear the ova develop to larvae and form the adult tapeworm.
Diphyllobotrium latum may cause severe anemia since it utilizes the vitamin B12 of the host diet.
It is common in North Europe and also USA. Fish should therefore not be eaten raw or undercooked specially fresh-water pike.


Hymenolepis nana

It causes the dwarf tapeworm infection. It is a very small tapeworm which does not need an intermediate host. The ova may remain in the intestine and develop to the larval form and finally to the adult tapeworm. In this way heavy infestation can take place.
Contamination takes place through fecal contaminated food and hands. Mice and rats may also bear Hymenolepis nana.


Hymenolepis diminuta

Hymenolepis diminuta (rat tapeworm, adults measuring 20 to 60 cm in length). Hymenolepis diminuta is a cestode of rodents infrequently seen in humans and frequently found in rodents.


Echinococcus granulosus

It causes the hydatid cyst. The adult stage lives in dog. The ova of the dog feces when ingested by sheep, hogs or cattle develops as larvae in the liver. If dogs feed from these animals during slaughter the ingested ova develop to adult tapeworms. Human beings may contaminate itself ingesting ova from food or hands contaminated by feces of dogs.This kind of contamination is common in sheep-raising countries. The ova so ingested develops to the larval form which penetrates liver or other organs forming the hydatid cyst which is a bladder-like growth containing fluid and many small capsules with scolices inside. The cyst may grow for years and cause severe reactions. Cutaneous larval migration:Larvae of the dog and cat hookworms can infect humans as unnatural hosts. They will not turn into adult worms. The larvae remain in the skin where they continue to migrate for months, causing a creeping eruption under the skin and die at the end. Treatment is surgical removal of the migrating larvae. A common source of infection are sandboxes contaminated by cats. Sandboxes are ideal environment for the hookworm eggs to develop and hatch and for the larvae to survive. Keep sandboxes covered. Other places where cats like to go are flower beds and vegetable gardens.

Cats and dogs should be kept away from food production and vegetable farming.

Recent records indicate that the prevalence of cystic echinococcosis is increasing in Russia, suggesting that dogs are used there in herding. [107]

Other pet parasites

There are several examples of parasites that are normally found in pets which can be transmitted to humans:


Dipylidium caninum

It is the common tapeworm of dogs. It can be transmitted to humans.
The life cycle of Dipylidium caninum involves dogs or cats as the definitive host and fleas or lice as the intermediate host. The flea or louse ingests the eggs. The dog or cat (or human) is infected when they ingest a flea or louse infected with the cysticercoids. Fleas or louse on dogs and cats should be eliminated as they transmit not only bacteria, viruses but also parasites.

Mesocestoides lineatus

Mesoscestoides tapeworm is a common cestode in carnivorous mammals, but human infection with the tapeworm of this genus have been infrequent.


Taenia pisiformis

Immature forms of the common roundworm of dogs, Toxocara canis can also cause migration in human visceral tissue. The feces of an infected dog or cat (or human) may contain proglotids of Taenia pisiformis.


Echinococcus multilocularis

The "small fox tapeworm" Echinococcus multilocularis causes alveolar echinococcosis (AE) in intermediate hosts. It is a small tapeworm (less than 4,5 mm in lenght) that parasites red and arctic foxes (dogs and cats are the definitive hosts). It is found in wild foxes in parts of Europe, Siberia, China, Japan, and arctic Alaska and in foxes and coyotes in Canada and north-central North America.

Definitive hosts are always carnivores.In the definitive hosts the adult tapeworm, consisting of 2 to 6 proglottids, living attached to the luminal surface of the small intestine. The terminal proglottid contains mature eggs (ovoid, 30-40 µm in diameter). The embryonated eggs, the infectious stage, are long-lived and highly resistant to high and low temperature (more than 50° C and down to -40° C). The mature eggs are shed with faeces and are spread in the environment. It is assumed that the intermediate host acquires the infections through the ingestion of contaminated fruits and vegetables.

Human Alveolar Echinococcosis [108]

According to Schweiger and colleagues 2007 human alveolar echinococcosis, a hepatic disorder that resembles liver cancer, is a highly aggressive and lethal zoonotic infection caused by the larval stage of the fox tapeworm, Echinococcus multilocularis Humans and intermediate host animals acquire the infection by ingesting E. multilocularis eggs in contaminated food or water or by having close physical contact with infected foxes, dogs, or host faeces.

Annual incidence of human alveolar echinococcis increased recently in zwitzerland.with fox population highly increasing. The authors warn from an emerging epidemic of AE. Future trends will depend on the intensity of present and future contamination of the environment with E. multilocularis eggs as well as on the number of susceptible persons exposed to the parasite.

Increasing fox population has increased the infection pressure for a large part of the human population such as coyotes in the United States and Canada, as suitable definitive host of E. multilocularis have become established in suburban areas with moderate to dense human populations, and other canids such as domestic dogs as definitive hosts.

The authors conclude that public health authorities in echinococcosis-endemic areas should establish coordinated systems of continuous surveillance and risk assessment, combined with measures to reduce illness and death from AE in human populations They suggest control strategies,such as deworming of foxes and other wild canids by using anthelminthic baiting. target suburban areas that have high human and wild canid population densities.


Anisakis and Herring

Anisakis simplex (herring worm), Pseudoterranova (Phocanema, Terranova) decipiens (cod or seal worm), Contracaecum spp., and Hysterothylacium (Thynnascaris) spp. are anisakid nematodes (roundworms) that have been implicated in human infections caused by the consumption of raw or undercooked seafood.

To date, only A. simplex and Pseudoterranova decipiens are reported from human cases in North America. Anisakiasis is most frequently diagnosed when the affected individual feels a tingling or tickling sensation in the throat and coughs up or manually extracts a nematode.

In more severe cases there is acute abdominal pain, much like acute appendicitis accompanied by a nauseous feeling. Symptoms occur from as little as an hour to about 2 weeks after consumption of raw or undercooked seafoods. (SUSHIS). With their anterior ends, these larval nematodes from fish or shellfish usually burrow into the wall of the digestive tract (occasionally they penetrate the intestinal wall completely and are found in the body cavity).

Anisakis rarely reach full maturity in humans and usually are eliminated spontaneously from the digestive tract lumen within 3 weeks of infection. In cases where the patient vomits or coughs up the worm, the disease may be diagnosed by morphological examination of the nematode. (Ascaris lumbricoides, the large roundworm of humans, is a terrestrial relative of anisakines and sometimes these larvae also crawl up into the throat and nasal passages.)

Seafoods are the principal sources of human infections with these larval worms. The adults of A. simplex are found in the stomachs of whales and dolphins.

Fertilized eggs from the female parasite pass out of the host with the host's feces. In seawater, the eggs embryonate, developing into larvae that hatch in sea water. These larvae are infective to copepods (minute crustaceans related to shrimp) and other small invertebrates.

The larvae grow in the invertebrate and become infective for the next host, a fish or larger invertebrate host such as a squid. The larvae may penetrate through the digestive tract into the muscle of the second host. Some evidence exists that the nematode larvae move from the viscera to the flesh if the fish hosts are not gutted promptly after catching.

These parasites are known to occur frequently in the flesh of cod, haddock, fluke, pacific salmon, herring, flounder, and monkfish. Severe cases of anisakiasis are extremely painful and require surgical intervention.

Food Analysis

Candling or examining fish on a light table is used by commercial processors to reduce the number of nematodes in certain white-flesh fish that are known to be infected frequently. This method is not totally effective, nor is it very adequate to remove even the majority of nematodes from fish with pigmented flesh.

Identification guide for fish parasites in stained tissue sections [109]

Identification of protozoan and metazoan parasites is performed carried using a series of classical keys based upon the morphology of the whole organism. Bruno, Nowak and Elliot 2006 provide an additional guide to the identification of fish protozoan and metazoan parasites in stained tissue sections. Identification of protozoan and small metazoan parasites (such as Myxosporidia) are stressed, because small organisms are often not recognized during gross examination.


Parasitic worm Thelazia callipaeda infecting eye associated tissues [110]

Thelazia callipaeda is a parasitic nematode which causes "thelaziasis" (or "eyeworm" infestation) in humans, dogs and cats and other carnivores. It infects orbital cavities and associated tissues. Drosophila is the vector host, Amiota (Phortica) variegata (Diptera: Drosophilidae) in Europe, and Phortica okadai in China. These flies feed on tears and infects individuals residing in poor communities in Asia, particularly in China.

A second species, Thelazia californiensis Price, 1930, has been reported to infect humans in the United States. Diagnosis may be difficult when infestation is caused by small larval stages that are difficult to detect and identify, or only small numbers of nematodes are present and clinical signs resemble allergic conjunctivitis. [111]

Parasites of cetaceans

Oliveira et al. 2011 assessed the parasitic fauna of stranded dolphins and whales at the Pacific coast of Costa Rica were examined between 2001 and 2009. In striped dolphin (Stenella coeruleoalba) the prevalence of parasites was 89.5%. In dwarf sperm whale (Kogia sima) no parasites could be found. In this study the authors report that they found six species of cestodes (Strobilocephalus triangularis, Tetrabothrius forsteri, Trigonocotyle sp., Phyllobothrium delphini, Monorygma grimaldi, Tetraphyllidea gen. sp. plerocercoid), four digeneans (Nasitrema globicephalae, Brachycladium palliatum, B. pacificum and Oschmarinella albamarina) and four nematodes (Anisakis spp., Halocercus lagenorhynchi, Halocercus sp. and Crassicauda anthonyi). A commensal crustacean, Xenobalanus globicipitis, was also identified. [112]

Parasitic fauna of 14 species of cetaceans off the northeastern coast of Brazil, including the archipelago of Fernando de Noronha were examined bei Carvalho et al 2010. Parasites were fixed and preserved in 70% ethanol or alcohol-formalin-acetic acid solution (AFA), clarified in phenol and mounted on slides for morphological identification. Halocercus brasiliensis, Halocercus kleinenbergi, Stenurus globicephalae, Halocercus sp., Anisakis sp., Crassicauda sp. (Nematoda), Phyllobothrium delphini, Monorygma grimaldii, Scolex pleuronectis, Strobicephalus triangularis, Tetrabothrius forsteri, Tetrabothrius sp., Trigonocotyle sp., Diphyllobothrium sp. (Cestoda), Campula sp. (Trematoda), Bolbosoma sp. (Acanthocephala), Cyamus boopis, Syncyamus pseudorcae and Xenobalanus globicipitis (Crustacea) were found. [113]

Genetic analysis identifies three new definite hosts of Anisakis typica [114]

Anisakis typica collected from the cetaceans Peponocephala electra, Kogia breviceps, and Stenella clymene, found at the coastal waters of Brazil, were submitted to genetic analysis by Inigues et al. 2011. Identification was performed using the18S rDNA gene, ITS1, and specific Anisakis typica ITS regions amplified by PCR. The authors stress that the cetaceans P. electra, K. breviceps, and S. clymene, are therefore to be considered as new definitive hosts of Anisakis typica.

Tapeworm alters host behaviour to reach final host to complete life cycle [115]

Schistocephalus solidus is a tapeworm with a three-host life cycle. Free-swimming coracidia are eaten by copepods, the first host. After 2 weeks of development in copepods,the tapeworm can infest the second intermediate host, three-spined sticklebacks which soon presents altered behaviours, such as splash along at the surface of the water enhancing the vulnerability to fish-eating birds, the final host of S. solidus where it attains maturity, produces eggs and dies after about a week.

FDA Fish and Fishery Products Hazards and Controls Guidance [116]

Parasites of human concern

Parasites (in the larval stage) consumed in uncooked or undercooked seafood can present a human health hazard. Among parasites, the nematodes or roundworms (Anisakis spp., Pseudoterranova spp., Eustrongylides spp., and Gnathostoma spp.), cestodes or tapeworms (Diphyllobothrium spp.), and trematodes or flukes (Chlonorchis sinensis (C. sinensis), Opisthorchis spp., Heterophyes spp., Metagonimus spp., Nanophyetes salmincola, and Paragonimus spp.) are of most concern in seafood. Most of these parasites cause mild-to-moderate illness, but severe symptoms can occur. Roundworms may embed in the intestinal wall and cause nausea, vomiting, diarrhoea, and severe abdominal pain and sometimes may penetrate the intestine. Tapeworms can cause abdominal swelling and abdominal cramps and may lead to weight loss and anemia. Intestinal flukes (Heterophyes spp., Metagonimus spp., and Nanophyetes salmincola) may cause abdominal discomfort and diarrhea. Some intestinal flukes may also migrate to and damage the heart and central nervous system. Liver flukes (C. sinensis and Opisthorchis spp.) and lung flukes (Paragonimus spp.) may migrate to the liver and lung and sometimes cause serious problems in other vital organs.

The FDA recommends preventive controls during the processing of parasite-containing species of fish that are intended for raw consumption, such as sushi, cold smoked fish, maties (salted herring) or undercooked fish.

Pathogenic bacteria in fish products

The survival of pathogenic bacteria through cooking or pasteurization can cause consumer illness. The primary pathogens of concern are Clostridium botulinum (C. botulinum), Listeria monocytogenes (L. monocytogenes), Campylobacter jejuni (C. jejuni), pathogenic strains of Escherichia coli (E. coli), Salmonella spp., Shigella spp., Yersinia enterocolitica (Y. enterocolitica), Staphylococcus aureus (S. aureus), Vibrio cholera (V. cholera), Vibrio vulnificus (V. vulnificus), and Vibrio parahaemolyticus (V. parahaemolyticus).

It is not practical to target viral pathogens in cooking or pasteurization processes because of their extreme heat resistance. Viral pathogens should be controlled through a rigorous sanitation regime as part of a prerequisite program or as part of Hazard Analysis Critical Control Point (HACCP) itself.

FDA recommendations to controlling fish parasites and pathogen bacteria

The process of heating raw fish sufficiently to kill bacterial pathogens is also sufficient to kill parasites. Guidance concerning cooking and pasteurizing to kill bacterial pathogens is provided in Chapters 13 (hot smoking) and 16 (cooking and pasteurization).

The effectiveness of freezing to kill parasites depends on the temperature of the freezing process, the length of time the fish is held frozen, and the type of parasite appear to be the most important factors. For example, tapeworms are more susceptible to freezing than are roundworms. Flukes appear to be more resistant to freezing than roundworms.

Freezing and storing at an ambient temperature of -20° or below for 7 days (total time), or freezing at an ambient temperature of -35° or below until solid and storing at an ambient temperature of -35° or below for 15 hours, or freezing at an ambient temperature of -35° or below until solid and storing at an ambient temperature of -20°) or below for 24 hours are sufficient to kill parasites. Note that these conditions may not be suitable for freezing particularly large fish (e.g., thicker than 6 inches).

Brining and pickling may reduce the parasite hazard in a fish, but they do not eliminate it, nor do they minimize it to an acceptable level. Nematode larvae have been shown to survive 28 days in an 800 salinometer brine (21% salt by weight).

Trimming away the belly flaps of fish or candling and physically removing parasites are effective methods for reducing the numbers of parasites. However, they do not completely eliminate the hazard, nor do they minimize it to an acceptable level.

Climate change influencing parasites and pathogen development

Biological systems are responding to climate change [117]

According to Kovats and colleagues shifts in the distribution and behaviour of insect and bird species indicate that biological systems are already responding to the world'sclimate change. The authors point to the task of detection of health impact of vector-borne diseases (i.e. malaria, dengue, leishmaniasis, tick-borne diseases) caused by global change.

Parasites my skip evolutionary changes [118]

Brooks and colleagues say that the intersection of climate change with evolutionary conservative aspects of host specificity and transmission dynamics, called ecological fitting, permits emergence of parasites and diseases without evolutionary changes in their capacity for host utilization.

Climate warming may increase pathogen development [119]

Climate warming can increase pathogen development and survival rates, disease transmission, and host susceptibility. Recently, changes in El Ninho-Southern Oscillation events have had a detectable influence on marine and terrestrial pathogens, including coral diseases, oyster pathogens, crop pathogens, Rift Valley fever, and human cholera.

Integrative approaches to assess changes caused by global climate [120]

According to Hoberg and colleagues investigations of emerging infectious diseases associated with parasites in northern wildlife involved a network of multidisciplinary collaboratorsand incorporated geographic surveys, archival collections, historical foundations for diversity, and laboratory and field studies exploring the interface for hosts, parasites, and the environment. In this system, emergence of parasitic disease was linked to geographic expansion, host switching, resurgence due to climate change, and newly recognized parasite species. Such integrative approaches serve as cornerstones for detection, prediction, and potential mitigation of emerging infectious diseases in wildlife and persons in the North and elsewhere under a changing global climate.

The authors investigating parasitic diseases in northern wildlif stress that small changes in absolute temperatures can have substantial effects on the transmission dynamics of protostrongylid lungworms and muscleworms (species of Parelaphostrongylus, Protostrongylus, and Umingmakstrongylus), which cycle among the environment, gastropod (slug and snail) intermediate hosts, and ungulate (caribou, muskoxen, thinhorn sheep, moose) definitive hosts.

Freshwater parasites

A number of internal and external parasites are of importance in aquaculture.

Ciliates

Ichthyophthirius multifiliis [121]

The disease called "Ich" or "white spot disease" has been a problem to aquarists for generations. Fish infected with this organism typically develop small blister-like raised lesions along the body wall and/or fins.
Tavares-Dias, Lemos and Martins 2010 report that 64% of ornamental fish collected from the middle Negro River, State of Amazonas were parasitized by at least one parasite species. The authors found infection as follows: Monogenea 36.7%, Ichthyophthirius multifiliis (Ciliophora) 20.6%, Trichodina spp. (Ciliophora) 4.0%, Piscinoodinium pillulare (Dinoflagellida) 1.3%, Tetrahymena sp. (Ciliophora) 0.89%, and Procamallanus sp. (Nematoda) 0.4%. [122]

Chilodonella and Tetrahymena [123]

Dopheide et al. 2011 assessed the feeding preferences of the free-swimming filter feeder Tetrahymena sp. and the surface-associated predator Chilodonella sp. Both protozoans feed on bacteria such as Pseudomonas costantinii and Serratia plymuthica, found on bacterial biofilms, and exert an important impact on the morphology of such biofilms.

Climate change increases incidence of some parasitic diseases [124]

Global warming may increase the incidence of parasitic diseases. Karvonen et al. 2010 presented a long-term multi-pathogen data sets on the occurrence of pathogenic bacterial and parasitic infections in relation to increasing temperatures in aquatic systems.

The authors found that the prevalence of infections increased with temperature. Diseases caused by Ichthyophthirius multifiliis and Flavobacterium columnare increase with elevation of temperature of the water. However, Karvonen and colleagues caution that the biology of each disease and local conditions must be considered, because the incidence of some diseases respond inversely to a temperature increase, such as noted with diseases caused by Ichthyobodo necator, and some do not respond to temperature variations, such is the case of Chilodonella spp.

Piscinoodinium pillulare and Tricodina [125]

Nile tilapia from Brazilian fish farms were found by Jeronimo et al. 2011 to be infested by Piscinoodinium pillulare (Dinoflagellida), which was the most dominant parasite followed by Trichodina magna e T. compacta (Ciliophora), Cichlydogyrus sclerosus, C halli, C. thurstonae, Scutogyrus longicornis (Monogenoidea), copepodids Lernaeidae gen. sp. The authors reported higher infestations by protozoan during autumn and winter and higher infestations by metazoan in spring and summer.

Ambiphyra Apiosoma and Epistylis [126]

Ambiphyra and Apiosoma are a sessile ciliates that can be found on the skin, gills, and fins of fish. Both are not particularly pathogenic if present in low numbers, but in high numbers, these parasites can cause significant damage. Overpopulation and poor sanitation, high organic loads and deterioration of water quality are frequently associated with heavy infestations.

Apiosoma piscicola (Blanchard 1885) was reported from fry of Carassius auratus (Var. pengze) and Ctenopharyngodon idella during parasite surveys in May 2005 and June 2006 at Hongze Lake, China. Its synonyms, Glossatella cylindriformis (Chen 1955) and Apiosoma magna (Banina 1968), were clarified by Li et al 2011 in their study. [127]

Epistylis [128]

Wu et al 2011 describe the morphology of the oligohalobic peritrichous ciliate, Epistylis chlorelligerum Shen, 1980. Zooids of Epistylis. chlorelligerum are characterized by green-colored endoplasm containing symbiotic algae.

Capriniana [129]

Ferguson et al.2011 studies the impacts of parasites on Oregon coastal coho salmon (Oncorhynchus kistuch), identifying 21 different species of parasites, such as Nanophyetus salmincola, Myxobolus insidiosus, Apophallus sp., Sanguinicola sp., Trichodina truttae, Epistylis sp., Capriniana piscium, an unidentified metacercariae in gills, Myxobolus sp. in brain, Myxidium salvelini and Chloromyxum majori in kidney, Pseudocapillaria salvelini and adult digenean spp. in the intestine.

Flagellates

Hexamita [130]

Hexamita is a small intestinal Flagellate parasite commonly found in the intestinal tract of freshwater fish. Hexamita sp.with morphological characteristics similar to Hexamita meleagridis was identified in stunted diarrhoeic 1- 12 week old native turkey poults by Dezfoulian et al.2010.

Ichthyobodo [131]

Two Ichthyobodo species are known to infect Atlantic salmon (Salmo salar L.). Ichthyobodo necator sensu stricto (s.s.) is a freshwater parasite, and Ichthyobodo sp. II sensu Todal et al. (2004), found in both fresh- and seawater.

Isaksenet al. 2011 found that Ichthyobodo sp. II present a unique SSU rDNA sequences and different morphology, compared with Ichthyobodo necator ss. The authors concluded that Ichthyobodo sp. II. represents a novel species and propose the name Ichthyobodo salmonis sp. n.

Cryptobia [132]

Guo and Woo 2009 describe important fish parasites causing disease outbreaks in fish farms and transmission of diseases between farmed and wild fish. The authors highlight the importance of four economically important fish parasites: Cryptobia salmositica (haemoflagellate), Loma salmonae (microsporidian), Gyrodactylus salaries (monogenean), Lepeophtheirus salmonis (copepod), and Caligus rogercresseyi (copepod).

Myxozoa [133]

The Myxozoa are a group of parasitic animals of aquatic environments. Many have a two-host lifecycle, involving a fish and an annelid worm or bryozoan.

The most significant diseases worldwide caused by myxosporeas in cultured fishes are PKD-Proliferative Kidney Disease, caused by a Malacosporea member,Tetracapsuloides bryosalmonae, and whirling disease, caused by a Myxosporea member Myxobolus cerebralis; both diseases affect salmonids. Furthermore, Enteromyxosis is caused by Enteromyxum leei in cultured marine sparids, while "Hamburger disease” or Proliferative Gill Disease is caused by Henneguya ictaluri in catfish and Sphaerosphora renicola infections occur in common carp.

Microsporidia [134]

All microspoidia are intracellular parasites that require host tissue for reproduction. They invade vertebrates and invertebrates. such as insects, crustaceans, fish and humans. The microsporidia have recently been recognized as a group of pathogens that have potential for waterborne transmission. Of primary concern are the microsporidian species that infect the human gastrointestinal tract, Enterocytozoon bieneusi and Encephalitozoon syn. Septata intestinalis. they present a special challenge to the water treatment industry with regard to detection and filtration. Wolk et al. 1999 presented a spore counting and cell culture model for microsporidia. [135]

Eimeria

Eimeria is a genus of parasites that includes various species responsible for the poultry disease coccidiosis. Eimeria are a member of the suborder Eimeriorina of the phylum Apicomplexa.

Human infections

Five genera are known to cause infections in humans: Cryptosporidium, Cyclospora, Isospora, Sarcocystis and Toxoplasma. Of these the first three normally are confined to the gastrointestinal tract and cause diarrhoea and abdominal pain. The other two invade the body tissues and many be found in multiple organs. [136]

Coccidiosis [137]

Coccidiosis is a parasitic disease of the intestinal tract of animals, caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue. Diarrhea, which may become bloody in severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic; however, young or immuno-compromised animals may suffer severe symptoms, including death.

While coccidian organisms can infect a wide variety of animals, including humans, birds, and livestock, they are usually species-specific. One well-known exception is toxoplasmosis caused by Toxoplasma gondii.

Genera and species that cause coccidiosis

Genus Isospora is the most common cause of intestinal coccidiosis in dogs and cats and is usually what is meant by coccidiosis. Species of Isospora are species specific, meaning they only infect one type of species, such as Isospora canis, Isospora ohioensis, Isospora burrowsi, and Isospora Neorivolta which infects dogs. Isospora felis and Isospora rivolta infect cats. The most common symptom is diarrhea.

Genus Cryptosporidium contains Cryptosporidium parvum and Cryptosporidium Muris infecting cattle and other mammals including humans. Cryptosporidium hominis is specific for immunocompromised individuals, such as humans, dogs and cats.

Genus Hammondia does not cause disease. It is transmitted by ingestion of cysts found in the tissue of grazing animals and rodents. Hammondia heydorni infecting dogs. Hammondia hammondi and Hammondia pardalis infecting cats.

Genus Sarcocystis infect carnivores such as dogs and cats that ingest cysts from various intermediate hosts.

Genus Toxoplasma has one important species, Toxoplasma gondii. Cats are the definitive host but all mammals and some fish, reptiles, and amphibians can be intermediate hosts. Only cat feces will hold infective oocysts but infection through ingestion of cysts can occur with the tissue of any intermediate host.

Eimeria Transcript Database

The assembled transcripts of the three Eimeria species Eimeria acervulina, Eimeria maxima and Eimeria tenellaare are published in the the Eimeria Transcript Database (EimeriaTDB)

The Eimeria Transcript Database (EimeriaTDB) is an integrated resource of cDNA sequencing and annotation data of Eimeria spp. of domestic fowl. EimeriaTDB is maintained by the Coccidia Molecular Biology Research Group at the Institute of Biomedical Sciences, University of São Paulo, Brazil. [138]

Parasites of the genus Eimeria infect a wide range of vertebrate hosts, including chickens. The Eimeria Transcript Database contains the transcriptomes of Eimeria acervulina, Eimeria maxima and Eimeria tenella, All cDNA reads have been assembled, and the reconstructed transcripts. The main goal is to offer a public repository of sequence and functional annotation data of reconstructed transcripts of parasites of the genus Eimeria. [139]

New Zealand native passerines are hosts to a large variety of gastrointestinal parasites, including coccidia. Schoener et al. 2013 found a prevalence of coccidian infection in the New Zealand bird species up to 38 %, primary of the family Eimeriidae. [140]

The prevalence of coccidia infection in goats were found by Balicka-Ramisz et al. 2012 to be up to 100% in Poland and Ukraine. Nine Eimeria spp. were identified in feces samples in Western Pomerania and Lviv regions: E. arloingi, E. chrisienseni, E. jolchijevi, E. ninakohlyakimovae, E. alijevi, E. capina, E. caprovina, E. hirci, E. apsheronica. The prevalence of infection in Western Pomerania of adult goats was 74% and 100% in kids. The results of the present investigation have implications for the control of coccidial infections in goats in Europe. [141]

Toxoplasmosis and Neosporosis in beef cattle in Thailand

Wiengcharoen et al. 2012 report that beef cattle in Thailand had a greater exposure to Toxoplasma gondii than Neospora caninum, and they should be regarded as a potential source of Toxoplasma gondii infection to humans. According to the authors neosporosis, despite low prevalence, is still a risk for morbidity among cattle, including abortions in Thailand. [142]

He et al. 2013 present a specific diagnostic assay using the Neospora caninum 40-kD surface antigen (p40) which is a marker for the diagnosis of neosporosis. The rNcp40 ELISA developed by the authors is a sensitive assay for detecting neosporosis in cattle. [143]

Two new species of coccidia identified

Jeanes et al. 2013 describe two new species of coccidia found in faeces of corncrake (Crex crex) in Scotland (U.K.). The new genes, Eimeria crecis n. sp. and Eimeria nenei n. sp. are widespread and cause enteric disease in corncrakes. [144]

Coccidia

Coccidia are intracellular parasites found in wild-caught and cultured fish. They are potential pathogens. According to Bangoura 2011 the pathogenic coccidia species Eimeria bovis and Eimeria zuernii are widespread in German dairy and fattening facilities. Eimeria oocysts were found positive in 95.4% of samples. Eimeria bovis was found in 76.9% of samples and Eimeria. Zuerniib in 83.1%. The number of oocysts excreted depended on the floor type, the age of the calves and the time after rehousing. Eimeria zuernii had a greater influence on the occurrence of diarrhoea than Eimeria bovis. The authors concluded that control measures to reduce coccidia incidence should be improved in Germany. [145]

Detection of coccidian parasites [146]

Honma, Suyama and Nakai 2011 investigated the coccidian parasites in cranes using faecal DNA using polymerase chain reaction-based capillary electrophoresis (PCR-CE), employing genetic markers in the second internal transcribed spacer (ITS2) of nuclear ribosomal DNA to detect crane coccidia. The authors stress that the sensitivity of detection of PCR-CE using faecal DNA was inferior to that with traditional microscopy, but was superior in solving the coccidia diversity and describe the community composition of the parasites in a host population.

Monogenean Trematodes

Monogenean trematodes, also called flatworms or flukes, commonly invade the gills, skin, and fins of fish. Monogeneans have a direct life cycle (no intermediate host). Gyrodactylus and Dactylogyrus are the two most common genera of monogeneans that infect freshwater fish

Digenean Trematodes

Digenean trematodes have a complex life cycle involving a series of hosts. The genus Posthodiplostonum has caused mortalities in baitfish.

Nematodes

Nematodes, also called roundworms, occur worldwide in all animals. They can infect all organs of the host, causing loss of function of the damaged area.

Camillanus and Capillaria: Camillanus protrudes from the anus of the fish which makes identification easier. Camillanus and Capillaria are the most frequent infestations of fish.

Cestodes

Cestodes, also called tapeworms, are found in a wide variety of animals, including fish. The life cycle of cestodes is extremely varied with fish used as the primary or intermediate host. Cestodes infect the alimentary tract, muscle or other internal organs.

One of the most serious adult cestodes that affect fish is the Asian tapeworm, Bothriocephalus acheilognathi. According to Bean and Bonner 2010 the Asian fish tapeworm Bothriocephalus acheilognathi in the Rio Grande raised concern about imperiled fishes. The prevalence of Bothriocephalus acheilognathi infestation was found to be 15% in samples of red shiners in January-March and December and below 10% during April-June and October. The authors stress that over 50% of the Rio Grande fish fauna in Texas are considered imperiled. A new stress caused by the Asian fish tapeworm in combination with reduced water quantity and quality and increased habitat fragmentation is of concern. [147]

Parasitic Crustacea

Parasitic crustacea are increasingly serious problems in cultured fish and can impact wild populations.

Ergasilus: Ergasilus infestations affect the gills of freshwater fish, commonly seen in warm weather. Dezfuli et a. 2011 assessed the immunobiology of sea bream, Sparus aurata L. infected with the important parasitic copepod Ergasilus sp. Their study revealed that the sea bream respond to massive infections of Ergasilus sp.sending mast cells and their antimicrobial peptides (AMPs). [148]

Lernaea

Lernaea , or anchor worm , is a common parasite of goldfish and koi. Hemaprasanth et al. 2011 studied the susceptibility of fingerlings of different species of carps to Lernaea cyprinacea infection. Cyprinus carpio, Labeo rohita and Labeo calbasu were found to be resistant to Lernae infections in monocultures, but only Labeo calbasu resisted to the infection when the carps were reared under polyculture conditions.The authors concluded that Labeo calbasu is the most resistant to Lernaea cyprinacea infections. Monoculture of the discussed carp species are suggested to control this parasite in culture ponds.[149]

Argulus

Freswater lice Argulus siamensis: According to Saurabh, Mohanty and Sahoo 2011 there are no suitable measure known to control the crustacean ectoparasite, Argulus which threatens carp cultures. The authors looked at the different expression of TLR 22-like, lysozyme G, beta 2-microglobulin genes, CXCa, lysozyme C, TNFalpha and complement component 3 (C3) between uninfected control and different degrees of lice infected fish. The majority of the genes showed down-regulation in kidney tissue whereas up-regulation in liver and skin tissues except C3 in Argulus-infected fish. The authors concluded that infection with Argulus siamensis result in immune gene expression changes in tissues situated away from the site of parasite attachment and feeding. This knowledge may be important to develop a control strategy for Argulus infections.

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143
He P, Li J, Gong P, Liu C, Zhang G, Yang J, Tuo W, Yang B, and Zhang X.
Neospora caninum surface antigen (p40) is a potential diagnostic marker for cattle neosporosis.
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144
Jeanes C, Vaughan-Higgins R, Green RE, Sainsbury AW, Marshall RN, and Blake DP.
Two new eimeria species parasitic in corncrakes (crex crex ) (gruiformes: Rallidae) in the united kingdom.
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145
Bangoura B, Mundt HC, Schmäschke R, Westphal B, and Daugschies A.
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Parasitol Res, 8 2011.
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146
Honma H, Suyama Y, and Nakai Y.
Detection of parasitizing coccidia and determination of host crane species, sex and genotype by faecal dna analysis.
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147
Bean MG and Bonner TH.
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148
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149
Hemaprasanth, Singh R, Raghavendra A, Sridhar N, Raghunath MR, and Eknath AE.
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