Studies of polymorphonuclear leucocyte function and of gross and microscopic lesions in sheep experimentally infected with Trypanosoma brucei and T. congolense

Polymorphonuclear leucocyte (PMN) function was assessed in trypanosome-infected sheep to establish its possible contribution to lowering of body defence. Sheep were inoculated with Trypanosoma congolense and T. brucei. Each infected sheep received eight million trypomastigotes intravenously.

Although sheep infected with T. congolense developed parasitaemia, there were no clinical signs of trypanosomiasis. Sheep infected with T. brucei developed parasitaemia, clinical signs of trypanosomiasis and alteration in PMN function. PMNs obtained from infected sheep had significant decrease in superoxide anoin production and nylon wool adherence, but enhanced phagocytosis of opsonized zymosan.

Clinical disease of T. brucei infection in sheep was characterized by pyrexia, anorexia, weight loss, anaemia, and inflammatory edema of skin of the head, neck, brisket, distal limbs, and tail. At the end of the trial, the sheep were euthanised and examined for lesions. There was edema of the skin and enlargement and edema of superficial lymph nodes. Microscopic lesions were observed in the skin, superficial lymph nodes, spleen and kidneys. Skin lesions consisted of severe edema accompanied by diffuse perivascular and periadnexal dermatitis, perineuritis, lymphangitis, distension of lymphatic vessels with fluid, and lymphatic thrombosis in the dermis and subcutis. Inflammatory reaction extended deep into subcutis leading to severe panniculitis and myositis. Inflammatory cells were mainly macrophages, plasma cells, and lymphocytes although polymorphonuclear leucocytes were also present. Numerous trypanosomes were seen in skin lesions. Superficial lymph nodes had severe capsular lymphadenitis and lymphoid hyperplasia. The spleen had lymphoid hyperplasia. Lesions in the kidney consisted of mild to moderate glomerulonephritis and a few tubular casts. (Abstract shortened by UMI.).