Clinical, serologic, and pathologic changes in calves with experimentally induced Trypanosoma brucei infection

In 7 calves inoculated with Trypanosoma brucei and observed for 105 days, the minimal clinical signs were occasional lethargic periods associated with parasitemia. Rectal temperatures increased by postinoculation day (pid), 10, remained moderately high until PID 50 to 60, and then returned to base line. Moderate anemia occurred between PID 15 and 25. Slightly increased lymphocyte count with relative decrease in neutrophil count was found in 3 calves. Monocytosis of minimal degree occurred 14 days after parasitemia. Trypanosome counts of low level and irregular frequency were found throughout the infection. The average number of trypanosomes in blood was approximately 1,000/ml. Antibody titers, as determined by the indirect immunofluorescent antibody method, appeared on PID 22 and stayed at moderate levels. The immunoglobulin M first increased at PID 5 and remained high (av 216% of base line value) throughout infection, but immunoglobulin G was never increased. Histopathologic study revealed proliferative changes in the lymph nodes and spleen characteristic of humoral antibody (B-cell) response. Mononuclear cell infiltration (lymphocytes and plasma cells), eosinophols, and edema were common in the lymph nodes, spleen, liver, heart, brain, hypophysis, testes, kidney, skeletal muscle, adrenal gland, pancreas, and uterus.