Saturday, 19 January 2008

Possible protozoa pathogens - Eunice

Protozoa (vector-bourne/foodborne)

1. Plasmodium species
Widespread in tropical and subtropical regions, including parts of the Americas, Asia, and Africa. Plasmodium vivax and Plasmodium falciparum are predominant in Southeast Asia.

· Infection is initiated following a bite from a female anopheline mosquito.

· When an infected mosquito pierces a person's skin to take a blood meal, sporozoites in the mosquito's saliva enter the bloodstream and migrate to the liver
· sporozoites infect hepatocytes, multiplying asexually and asymptomatically into numerous merozoites which would rupture from liver cells to the circulatory system to infect RBCs.
· Within the red blood cells, the parasites multiply from merozoites into trophozoites (ring form) then into schizont.
· Some P. vivax and P. ovale sporozoites may develop into hypnozoites that remain dormant for periods.
· After mature schizont formed, RBCs rupture releasing merozoites and the newly released meozoites will repeat the whole cycle by infecting other RBCs.

· fever, shivering, arthralgia (joint pain), vomiting, anaemia caused by hemolysis, hemoglobinuria, and convulsions.
· severe malaria may cause coma and death if untreated, splenomegaly, severe headache, cerebral ischemia, hepatomegaly, hypoglycemia, and hemoglobinuria with renal failure may occur.

· Wear long sleeves and long pants; sleep in sleeping nets if possible.
· Application of mosquito repellent.

2. Toxoplasma species
Toxoplasmosis is a parasitic disease caused by protozoan Toxoplasma gondii. The parasite infects most warm-blooded animals, including human.

· Ingestion of raw/ partly cooked meat containing Toxoplasma cysts.
· Drinking water contaminated with Toxoplasma

· Ingestion of oocytes or tissue cysts in improperly cooked meat becomes infected.
· The parasite enters marcophages in the intestinal lining and is distributed via the blood stream throughout the body.
· Focal areas of necrosis may develop in a variety of organs and the clinical manifestations reflect injury to specific tissues.

· influenza-like: swollen lymph nodes, or muscle aches and pains that last for a month or more.

· ensure food are well-cooked
· avoid contact with rodent and its excreta
· wash utensils and hands before handling food

3. Helminths – Wuchereria bancrofti
Itis a parasitic filarial nematode worm spread by a mosquito vector It is one of the three parasites that cause lymphatic filariasis. Can be found in tropical and sub-tropical countries.

· disease spread by mosquito bites
· All worm offspring are passed on through poorly cooked meat, especially pork, wild fish, and beef, contaminated water, feces, mosquitoes and, in general, areas of poor hygiene and food regulation standards such as parts of Africa, Central and South America and Asia

· The microfilaria are present in the circulation. The microfilaria migrates between the deep and the peripheral circulation.
· During the day they are present in the deep veins and during the night they migrate to the peripheral circulation.
· the worm is transferred into a vector; the most common vectors are the mosquito species: Culex, Anopheles, Aedes, and Mansonia, and when current host feeds, and it is egested into the blood stream of its new human host.
· The larvae moves to the lymph nodes, predominantly in the legs and genital area, and develops into adult worm over the course of a year. By this time, an adult female can produce microfilariae itself.

· swelling, granulation lesions, and impaired circulation, the lymph nodes are enlarged and dilated.
· affected tissue will expand and elephantiasis, will result, followed sometimes by death.

· Wear long sleeves and long pants; sleep in sleeping nets if possible.
· Application of insect repellent.

4. Leishmania species
Leishmania is a genus of trypanosome protozoa, and is the parasite responsible for the disease leishmaniasis. Leishmaniasis can be transmitted in many tropical and sub-tropical countries

· transmitted by the bite of certain species of sand fly

· Bite of female phlebotomine sandflies will inject the infective stage, metacyclic promastigotes, during blood meals.
· Metacyclic promastigotes that reach the puncture wound are phagocytized by macrophages and transform into amastigotes which will multiply in infected cells and affect different tissues.

· fever, damage to the spleen and liver, and anaemia.

Foodborne protozoa
Gardia, Cryptosporidium and Cyclospora (covered in elaine's post) are intestinal protozoan parasites that parasitise in both human and non-human host. There is increasing evidence that these organisms are significant contaminants of food.
Food consumed raw or lightly cooked, with viable oocytes has been responsible for several outbreaks of giardiasis, cryptosporidiosis and cyclosporiasis.

References:> malaria parasite> toxoplasmosis> helminths> wuchereria bancrofti> leishmania

Book: Foodborne pathogens: hazard, risk analysis and control / edited by Clive de W. Blackburn and Peter J. McClure

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