Trypanosomal cardiac valvulitis in vervet monkeys.

Quarantined vervet monkeys (Cercopithecus aethiops) were infected with Trypanosoma brucei (10(4) parasites/animal) in a tsetse free area. Thirteen monkeys (11 infected with T.b. rhodesiense and 2 with T.b. brucei) were studied. Animals became parasitaemic within one week after infection. The infection time lasted between 21 and 129 days; in 8 monkeys it was between 50 and 70 days. Macroscopically massive pericarditis was observed in one, pericardial effusion in one, small apical aneurysms in three. Microscopically all had pancarditis of moderate to marked degree including all 4 chambers, the apices and the valvular appendages. Trypanosomes and inflammatory cells were found in the interstitium of the 3 cardiac layers. Lymphatic drainage of trypanosomes and inflammatory cells was seen in all hearts, the lymphatic vessels showing signs of stasis. By light microscopy trypanosomes and inflammatory cells were also shown to occur in all four types of heart valves implicating diffuse valvulitis. In two instances electron microscopy confirmed the intact presence of the trypanosomes clustering in great numbers in the pars elastica of the valves. In the collagenous part, some intact single trypanosomes were seen between collagen fibres. No amastigotes were observed. These results point to select sites in organ topography which in turn may be relevant to active disease, chemotherapy and healing. The possibility of hiding places within the heart - protecting trypanosomes from the host defense and/or chemotherapeutic agents - ought to be considered.