Objective:To investigate the effects of combination therapy of methanolic leaf extract of Azadirachta indica(A.indica) and diminazene diaceturate(DDA) in the treatment of experimental Trypanosoma brucei brucei(T.brucei brucei) infection in rats.Methods:Acute toxicity study of the drug and extract combinations were done.Selection of the best drug and extract combinations was carried out using fifty four rats of both sexes separated into 9 groups.Three dose combinations were derived from selection of the best drug and extract combinations used for the final study viz:7 mg/kg bw DDA plus 125 mg/kg bw extract(group B),3.5 mg/kg bw DDA plus 250 mg/kg bw extract(group C),and 1.8 mg/kg bw DDA plus 500 mg/kg bw extract(group D).The final study had in addition to the three groups derived from the dose response study,four other groups viz:uninfected untreated negative control(group F),infected and treated with 3 000 mg/kg bw extract alone(group E),infected and treated with 7 mg/kg bw DDA alone(group A),and infected untreated positive control(group G).The parameters assessed were onset of parasitaemia(OP), level of parasitaemia(LOP),clearance of parasites post treatment(COPPT),relapse infection period(RIP),post infection survival period(PIST).Results:There was no significant difference in OP between the groups(P<0.05).One day post treatment,the mean LOP of groups A,B,and C were found to be significantly lower than that of group D which in turn was lower than that of group E and G respectively.The mean LOP of group E was significantly lower than group G two days post treatment and this trend continued throughout the experimental period.Mean COPPT of group D was significantly longer than that of groups A,C and B.There was no significant difference in the mean COPPT among groups B,C and A.The mean RIP of group D was significantly shorter than group C,and that of group C was significantly shorter than that of group A.There was no relapse of infection in group B.The PIST of group E did not differ significantly from group G.Conclusions:This experiment stands to conclude that combination of 125 mg/kg bw extract and 7 mg/kg bw DDA is very effective in the treatment of trypanosomosis,caused by T. brucei.This combination therapy proved to be better than single therapy of DDA.
