Trypanosoma evansi is a flagellate protozoan that causes a disease characterized by high parasitemia and acute anemia in various species. This study was aimed at evaluating and establishing a relationship between different parasitemia levels and eritropoyesis in Wistar rats (Rattus norvegicus) experimentally infected by T. evansi. Forty two animals were used. In 36 animals parasites were inoculated by intraperitoneal blood injection of 0.2ml containing 2.5x104 parasites. Six non-inoculated animals were used as controls. Parasitemia was evaluated every 12 hours and the animals were allocated in groups according to parasitemia levels. Then they were classified according to average number of parasites in 10 random homogeneous fields, Group A: control (not-inoculated); B: rats with 1-10 trypanosomes/field; C: 11-20 trypanosomes/field; D: 21-30 trypanosomes/field; E: 31-40 trypanosomes/field; F: 41-50 trypanosomes/field; G: more then 51. Blood samples were taken when the animals reached the correspondent group number of parasites. Hemogram and iron levels were evaluated and a bone marrow cytology was performed to detect the myeloid:erythroid ratio. Statistical analysis showed a significant reduction on red blood cells count and hematocrit from group E on and also hemoglobin on groups F and G. The myeloid:erythroid ratio reduced from 0.7 to 0.6 on groups F and G (P<0.005). Iron levels alterations were not detected. These data showed that Wistar rats with parasitemia higher then 31 parasites per field have an acute anemia associated to a compensatory hematopoietic activity.
Trypanosomiasis; hematology; hematopoietic activity; seric iron; bone marrow; Rattus norvegicus