Thrombocytopenia and increased clotting time in rats acutely infected by Trypanosoma evansi

The aims of this study were to evaluate clotting disturbances in the acute infection by Trypanosoma evansi in rats and to investigate two possible causes. To address this issue, 21 2-month-old male rats were separated into three groups with seven animals each. The control group (group I) was composed of non-infected animals and group II was composed of 14 T. evansi-infected animals. This group was subdivided into two homogeneous groups. Animals from group II-a and from group II-b were euthanized at days 3 and 5 post-inoculation (PI), respectively. Hematological parameters were evaluated for monitoring of the disease. Infected animals showed anemia and leukocytosis 3 days PI and a significant decrease was observed in platelet count at days 3 and 5 PI. The prothrombin time (PT) and activated partial thromboplastin time (aPTT) were longer in the infected groups. The averages of the megakaryocyte count significantly increased (P < 0.05) in group II-b (5 days PI). Splenomegaly was observed in all T. evansi-infected rats at necropsy. Based upon the results, it is concluded that the acute infection by T. evansi in rats causes thrombocytopenia and longer prothrombin and activated partial thromboplastin times. In response to the thrombocytopenia, an increased number of bone marrow megakaryocytes were observed in the infected rats. Thus, the decrease in circulating platelets may be a consequence of splenic sequestration.