Medically Important Protozoa (3)

Cryptosporidiosis. Cryptosporidium parvum causes diarrhea disease mainly in infants and small children. It is normally self-limiting but in the immunocompromized host the disease can be severe. C. parvum is enzootic in young calves and is usually passed to man in water containing oocysts of the organism. Toxoplasmosis. Toxoplasma gondii causes the multi-organ infection of toxoplasmosis. The domestic cat is the definitive host for T. gondii from which man and other mammals can become infected. Infection commonly arises from the consumption of under cooked meat and in the healthy adult is usually asymptomatic. The most devastating form of toxoplasmosis is seen in congenital infection when a pregnant mother passes the organism to the fetus. This can result in severe abnormalities at birth. The life-cycle of T. gondii is complex, involving both sexual and asexual reproduction. Three main life forms of T. gondii occur: (i) the oocyst which is produced from the sexual cycle in the small intestine of the cat and contains sporozoites; (ii) the tachyzoite of the asexual invasive form found in secondary hosts which are derived from pseudocysts; and (iii) the tissue cyst that contains bradyzoites.
Microsporans
The medical importance of microsporidial infections has only recently been highlighted by the frequent recognition of these obligate intracellular parasites in material from patients with HIV infection and AIDS. Examples are: Encephalitozoon species, Nosema species and Septata intestinalis. Multi-organ infections occur and S. intestinalis is found in about 2% of all AIDS patients with chronic diarrhea.
Source: University of Leicester
References: Baker, J.R. and Muller, R (Eds). Advances in Parasitology. Academic Press, London. Knight, R. (1982). Parasites Diseases in Man. Churchill Livingstone, London. Peters, W. and Gilles, H.M. (1995) Colour Atlas of Tropical Medicine and Parasitology. Mosby-Wolfe.