The pathogenesis of Trypanosoma congolense infection in calves. II. Anemia and erythroid response.

The anemia caused by Trypanosoma conogolense TREU 112 in Holstein calves was of moderate severity and normochromic, macrocytic in the acute phase changing to normochromic, normocytic with chronicity. The anemia was hemolytic and responsive as shown by sharply decreased myeloid:erythroid ratio and increased mean corpuscular volume. 51Cr red cell labelling studies showed that red cell lifespan was halved in the acute phase and there was an increase in plasma volume. Surface organ counting of liver showed it to be the major site of red cell destruction. The anemia was partly dilutional as a result of the increased plasma volume and primarily hemolytic likely of a non-specific immune (innocent bystander) pathogenesis.