Life Under the Microscope: Toxoplasma gondii

Toxoplasma gondii is the causative agent of the disease known as toxoplasmosis. The parasite was first discovered by Charles Nicolle and Louis Manceaux in 1908 while working with the rodent Ctenodactylus gundi. They initially named the parasite Leishmania gondii thinking that it belonged to the Leishmania genus. However, once they realized they discovered a new organism, they named it Toxoplasma gondii, from the Greek toxo, meaning arc or bow, and plasma, meaning something that is shaped or molded.  The parasite’s definitive host is the cat in which T. gondii can sexually reproduce.

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Toxoplasma gondii

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Life Under the Microscope: Trypanosoma brucei

First discovered by Sir David Bruce in 1894 and appropriately named after him, Trypanosoma brucei is the causative agent of African trypanosomiasis, also known as “sleeping sickness”. It is prevalent in tropical and subtropical regions of Africa. Trypanosoma brucei consists of a group of three organisms: T. brucei gambiense, T. brucei rhodesiense, and T. brucei brucei. While all of these organisms cause trypanosomiasis, T. brucei brucei only infects animals and is not pathogenic in humans. All of these organisms within the disease share the same vector, the tsetse fly.

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Tsetse fly, the vector of African trypanosomiasis

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Life Under the Microscope: Babesia microti

First reported by Victor Babes in 1888, Babesia microti is an intracellular parasite that infects red blood cells. The infection caused by this organism is known as babesiosis. Originally, Babes had thought the infection was due to the bacterium Haematococcus bovis, however, Theobald Smith and Fred Kilborne correctly identified the parasite as the causative agent in 1893. It was also first believed that this parasite only infected cattle, but again, they were proven wrong after observing a case within a splenectomised patient.

For infections occurring within the United States, the vector of the disease is the tick of the Ixodes species, also the vector of Borrelia burgdorferi , the bacterium that causes Lyme disease. For this reason, coinfections of babesiosis and Lyme disease are common.

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Ixodes scapularis, vector of babesiosis infections

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