Gross and Histopathological Alterations in Experimental Trypanosoma Evansi Infection in Donkeys and the Effect of Isometamidium Chloride Treatment

Abstract

Trypanosoma evansi (T. evansi) infection causes wasting and fatal animal trypanosomosis. This study was aimed at determining the gross and histopathological alterations in donkeys experimentally infected with T. evansi and the effect of isometamidium chloride treatment. Apparently healthy donkeys (N=18) of mixed sexes were randomly assigned to 3 groups; A1 (Infected-untreated), A2 (Infected, isometamidium-treated) and B (Uninfected, control) of six animals each. Each animal in infected groups had about 2.0x106 T. evansi injected through the jugular vein. Parasitaemia levels were evaluated using HCT and Mice Inoculation Test (support test). Gross and histopathological examinations were also conducted post-infection and post-treatment. Results, showed chronic-stage relapsed parasitaemia in infected-untreated group and much later in isometamidium-treated animals. Grossly, acute lesions were severe lungs congestion and frothy exudates in the trachea/bronchi while the chronic lesions were moderate gray hepatisation, hydrothorax, hydroperitoneum, serous atrophies of fats and mild adherence of renal capsule to the cortex. Histopathological lesions were chronic and involved the lungs (moderate to severe forms of congestion and mononuclear cellular infiltrations), spleen (severe forms of haemosiderosis and lymphocytes depletion at germinal centres) and liver (severe form of congestion, moderate focal necrosis and mononuclear cellular infiltrations). Isometamidium chloride-treated animals showed only moderate level of mononuclear cellular infiltrations in lungs while in spleen mild levels of haemosiderosis and lymphocytes depletion at germinal centres were the histopathological features. In conclusion, there is parasite relapse, the gross and histopathological lesions in experimental T. evansi infection in donkeys are pronounced in acute and chronic stages of infection manifesting as severe to moderate lesions in thoracic and peritoneal cavities, lungs, spleen, heart, kidneys and liver of animals that do not get treatment. Donkeys treated with isometamidium chloride, show relapsed parasitaemia, mild to moderate histopathological lesions in lungs and spleen with no gross lesions in chronic stage.