The pathogenesis of Trypanosoma congolense infection in calves. I. Clinical observations and gross pathological changes.

Holstein calves infected with Trypanosoma congolense TREU 112 had intermittent fever, debility and a poor hair coat. At postmortem examination the most significant findings were enlargement of the liver, kidneys and spleen and increased volume of hematopoietic marrow. A group of 13 calves infected for 18 weeks had marked enlargement of lymph nodes throughout the body and hemal nodes were prominent in the sublumbar area caudal to the kidneys. Another group infected for 7 weeks had no increase in the weight of lymph nodes. Studies with 51Cr labelled autologous red cells given shortly before postmortem examination showed that the liver was the most active organ with respect to sequestration of labelled red cells.