Subsections

Parasites and Pathogenic 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[960].


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$^{o}C$) 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$^{o}C$ 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. [961]

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. [962]

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.


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

[963]
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

[964]
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.

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. [965]

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. [966]

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. [967]

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. [968]

Giardia and Cryptosporidium spp agents of waterborne diseases

[969]
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. [973]

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. [970]

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. [971]

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. [972]

Methods for the diagnosis of Cryptosporidium and Giardia

[973]
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

[974]
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. [7]

New sub-genotype of Cryptosporidium parvum

[976]
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. [977]

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. [978]

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. [979]

Solar UV inactivates Cryptosporidium oocysts

[980]
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

[981]
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

[982]
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 feces

[983]
Oocysts survival in water: Cryptosporidium parvum oocysts are inactivated when exposed to a temperature of 72.4$^{0}C$ for 1 min or 64.2$^{0}C$ for more than 2 min. The lowest die-off rate was found at 4$^{0}C$. Freezingt is predicted to inactivate 99.99% of oocysts in 853 days at -4$^{0}C$ or 64 days at -22$^{0}C$.

The die-off rate for oocysts in river water at 5$^{0}C$ is similar to that in autoclaved river water, but at 15$^{0}C$, 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$^{0}C$,

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

Giardia canis virus as genetic tool to alter Giardia canis

[984]
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. [985]

Sewage treatment

[986]
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) [987], 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$^{0}C$ for at least 1 h is an effective approach to eliminate most pathogens.

Toxoplasma gondii

[988]
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. [989]

Reducing Toxoplasma infection risk

[990]


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 [991]

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. [992]


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
\includegraphics[width=122.43bp,height=165.61bp]{library/Ascaris.eps} Ascaris lumbricoides from infected humans.


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.

\includegraphics[width=350bp, height=350bp, angle=0]{library/Enterobius.eps}


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.

\includegraphics[width=420bp, height=450bp, angle=0]{library/spiralis.eps}


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 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

[993]
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

[994]
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

[995]
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. [996]

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. [997]

Fishborne intestinal parasites are a risk for raw fish eating community

[998]
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. [999]

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). [1000]


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.

[1001]
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.


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.

\includegraphics[width=450bp, height=450bp, angle=0]{library/Taenia.eps}


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. [1002]

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$^{o}$ C and down to -40$^{o}$ 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

[1003]
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.

Climate change influencing parasites and pathogen development

Biological systems are responding to climate change

[1004]
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

[1005]
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

[1006]
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

[1007] 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.

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