Pig trypanosomiasis: comparative anaemia and histopathology of lymphoid organs

Anaemia with characteristic clinical symptoms, haematological changes and histopathology of lymphoid organs, was observed following experimental infection of pig with pathogenic species of Trypanosoma brucei brucei and Trypanosoma congolense, the former being more virulent than the latter. Mean incubation periods were 4 and 7 days, and generalized fluctuating levels of parasitaemia and pyrexia without mortality were observed. Other symptoms included hyperaemia, petechial haemorrhages leading to plaques or lesions, inappetence, dehydration and/or ascites. Trypanosomiasis significantly (P less than 0.01) lowered the packed cell volume (PCV), haemoglobin concentration and red blood cells, but elevated white blood count (differentials) of infected pigs. Trypanosomes were localised in and destroyed the lymphoid tissues, the major lesions of which included haemorrhages, mononuclear infiltration prolification and distortion of follicles, and tissue necrosis or fibrosis. Significant effects of resultant immunosuppression, erythrophagocytosis and hence secondary infections to pig production in trypanosome endemic areas are highlighted.