African Trypanosomosis is a neglected tropical disease of medical and veterinaryrnimportance. Parasite control relies on the use of few drugs whose resistance andrnunacceptable toxicities urged the investigation of new agents, preferably from naturalrnsources. Though Dovyalis abyssinica has been reported to posses significant trypanocidalrnactivity on Trypanosoma brucei in in vitro model, activity on trypanosome infectedrnlaboratory animals has not yet been worked out. The aim of the present study was,rntherefore, to investigate the in vitro and in vivo activity of D. abyssinica on T. congolensernfield isolate. To evaluate the effect on motility, 200 Î¼l T. congolense infected blood wasrnmixed with 50 Î¼l of 20, 10, 2, 0.1, 0.015 mg/ml dichloromethane and methanol extracts.rnReduction or cessation of motility was then microscopically monitored for 120 minutes,rnand the remaining in vitro mixtures were inoculated to healthy mice and monitored forrndevelopment of infection for 21 days. Furthermore, fifty T. congolense infected micernwere randomly grouped into ten groups of five and administered with curative dosesrn(250, 200, 150 and 100 mg/kg) of dichloromethane and methanol and 28 mg/kgrndiminazene aceturate and dimethylsulfoxide. Following administration, parasitemia,rnpacked cell volume (PCV), rectal temperature, body weight and survival time wererniiirnmonitored. Suppressive doses of the extracts (250 and 200 mg/kg) were administered 24rnhours post-infection and parasitemia was monitored. Dichloromethane and methanolrnextracts at 20, 10, 2 mg/ml concentrations ceased parasite motility within one hour andrneliminated subsequent infectivity in mice for 21 days. Administration of dichloromethanernand methanol extracts at 250 and 200 mg/kg reduced (p