Susceptibility of Trypanosoma evansi to human blood and plasma in infected mice.

Around 1900 Laveran and Mesnil discovered that African trypanosomes do not survive in the blood of some primates and humans. The nature of the trypanolytic factor present in these sera has been the focus of a long-standing debate between different groups. The aim of this study was to investigate the susceptibility of T. evansi isolates to therapy using human blood and plasma in experimentally infected mice. Forty-eight 2-month-old female mice (Mus musculus) were divided into six groups of eight animals per group (A, B, C, D, E and F). Plasma was obtained after blood collection in order to perform therapy. Animals from group A (positive control) were inoculated with T. evansi and treated with 0.2mL of saline solution. Animals from groups B and C were infected with the flagellate and received a curative treatment with 0.2mL of human blood (group B) and 0.2mL of human plasma (group C), 24h after infection. Animals from groups D and E received a prophylactic treatment with 0.2mL of human blood and 0.2mL of human plasma, respectively, 24h prior to the infection. Animals from group F (negative control) were not infected and received 0.2mL of saline solution. The four treatments (B, C, D and E) increased animals longevity when compared to group A. Prepatency period was longer in groups D (15 days) and E (37.7 days) under prophylactic immunotherapy. Moreover, no parasites were found in most of the animals 60 days post-inoculation (PI). Besides the longer longevity, treatments were capable of curing 50% of mice of group B, 37.5% of group C, 37.5% of group D and 25% of the animals from group E.