The pathology of experimental Trypanosoma evansi infection in the Indonesian buffalo (Bubalus bubalis)

Six Indonesian buffaloes (Bubalus bubalis) were inoculated intravenously with 10(5) Trypanosoma evansi, examined clinically, haematologically and serologically, and then killed 1, 2, 3, 4, 8 or 12 weeks after infection for detailed pathological study. Relapsing fever was related to the waves of parasitaemia and fluctuations of pulse and respiration rates. Anaemic mucous membranes, depression, weakness, refusal to walk, loss of appetite and emaciation were seen. Body weight, packed cell volume, total platelet and red cell counts, and haemoglobin values were below those of two uninfected control buffaloes, as well as below the normal range; on the other hand antibody titres against T. evansi in infected animals were all above those in controls. Emaciation, serous atrophy of fat, hydropericardium, petechial to larger haemorrhages in the pericardium, pneumonia, congested liver and spleen, oedematous enlargement of the superficial lymph nodes and hyperplastic bone marrow were the major gross pathological changes. Histologically, the severity of the disease increased from 1 to 7 weeks after infection and became less obvious at 12 weeks. The most consistent lesions were interstitial pneumonia, interstitial myocarditis, splenic multifocal necrosis, interstitial myositis and hyperplastic bone marrow. The last three lesions appear not to have been reported previously in T. evansi infection in buffaloes or other animals. The clinicopathological findings in this study show that T. evansi is both an intravascular and extravascular parasite.