Haematological studies on Trypanosoma vivax infection of goats and intact and splenectomized sheep

Abstract

Trypanosoma vivax infection of sheep and goats, although manifesting varying severity in individual animals, was characterized by an initial phase of “crisis” lasting several weeks which was associated with high fluctuating parasitaemia, a marked drop in red cell values, leucopaenia and a transient macrocytosis which was later replaced by microcytosis. Many animals died during this phase. Animals which survived the crisis passed into a recovery phase characterized by low infrequent parasitaemia, a recovery of the red cell values, sometimes attaining pre-infection values, and leucocytosis. Mortality was generally higher in goats than in sheep and with “wild strains” isolated from cattle and inoculated directly into experimental animals than with the laboratory-adapted strain $\text{36}\text{15}$.

The anaemia associated with crisis was haemolytic, with a variable decrease in ⁵¹Cr-red cell survival, the degree of shortening being related to the degree of anaemia at the time of measurement. The spleen was the major site of red cell destruction in animals with mild anaemia while the liver was the major site in severely anaemic animals. The bone marrow showed erythroid hyperplasia early in crisis but terminally the percentage of erythrogenic elements drifted towards normal. There was a gross increase in the red marrow mass of the long bones, but regenerative forms of red cells were consistently absent from the blood of severely anaemic animals, suggesting some interference with marrow function.

Splenectomy reduced the incubation period of T. vivax in sheep but did not affect the duration and mortality of the disease, nor did it ameliorate the anaemia or affect the intensity and frequency of parasitaemia.