Saturday, 19 January 2008

Water borne protozoa_elaine

Protozoa: single-celled parasites

Infection with parasites is a major cause of morbidity and mortality in tropical and semitropical countries

--arthropod vectors
--intermediate hosts e.g. fishes or snail

1) Giardia Lamblia (giardiasis): A flagellated protozoon and an important cause of diarrhea worldwide.

[Route of infection]: Faecal-oral

[Pathogenesis]: cysts of Giardia Lamblia have been demonstrated in the drinking water. Ingestion of cysts—the resistance, infective stage—is followed by the production of trophozoites in the upper small intestine. Trophozoites cause irritation, which leads to gastrointestinal symptoms.

[Clinical features]
Symptoms: diarrhea, mild to severe, with characteristic light-coloured fatty tools; abdominal pain: cramps, with flatulence and epigastric tenderness; anorexia
Malabsorption: steatorrhoea is not common and may lead to the full-blown malabsorption syndrome.

Consume only treated water sources.

2) Cryptosporidium Parvum (Cryptosporidiosis): human infection is often acquired as a result of animal slurry contaminating water supplies.

The infective stage is the oocyst, passed in faeces: transmitted person-to-person, animal-to-person or via contaminated water.

[Clinical features]
Symptoms: self-limiting diarrhea in the immunocompetent individual.

Consume only treated water/clean water

3) Isospora Belli: humans seem to be the only host of this parasite, which infects the small intestine.

Faecal-contaminated food and water

[Clinical Features]
In the immunocompetent infection is often asmptomatic and the diarrhea, when present, tends to be mild.

Consume only treated water/clean water

4) Cyclospora Cayetanensis (Cyclosposiasis): infect the small intestines

The infective stage is the oocyst passed in faeces (waterborne)

[Clinical features]
Symptoms: diarrhea, remitting and relapsing, sometimes lasting as long as 6 weeks; malabsorption in some cases; weight loss

Consume only treated water/clean water

5) Entamoeba Histolytica (amoebiasis): a common infection in tropical countries such as Indonesia where the sanitation is poor.

[Route of infection]
Faecal-oral, owing to contaminated water

[Clinical features]
Diarrhea, progressing rapidly to bloody diarrhea accompanied by fever and painful abdominal cramps, symptoms may pesist into a chronic relapsing state. Sometimes progresses to dilatation of the colon, with the risk of intestinal perforation.

Amoebic absecess owning to spread to the liver causing painful enlargement and accompanied by high fever, raised white cell count and high ESR.

Consume only treated water/clean water

Book: Medical microbiology 4th edition. written by patrick R. Murray, Ken S. Rosenthal, George S. Kobayashi, Micheal A. Pfaller

Book: microbiology of waterborne disease. written by S L Percival, R M Chalmers

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