Abstract
Azadirachta Indica A Juss (Melliaceae) though a native of Asia is now cultivated throughout Nigeria is used in the treatment of fever and malaria, a disease caused by a protozoan parasite. In this present study, the activity of aqueous leaf extract of Azadirachta Indica was screened on Trypanosoma. (b) brucei infection in mice. Two doses of 500 and 250mg/kg were selected after acute toxicity study. Study groups were set up consisting of 5 (five) mice and these where: positive control, negative control, single dose treatment, and multiple dose treatment and prophylactic group. Percentage parasitemia, PCV, mean survival time and cumulative mortality were monitored. Results showed that survival period were significantly (P < 0.05) increased in multiple and prophylactic dosage groups in a dose dependent manner respectively.