The response of trypanosome-infected water buffaloes and cattle in different areas of fly challenge to normal therapeutic doses of trypanocidal drugs

Abstract

Laboratory examination of blood smears from water buffaloes in an area of high fly challenge indicated an infection rate of 51.11 % caused by both Trypanosoma congolense and T. vivax. A similar study in cattle raised in a low fly challenge area showed an infection rate of 22.73% caused by T. congolense only. Diminazene aceturate administered as a single dose at 3.5 mg/kg body weight cured the infection in cattle, while a similar dose at 7 mg/kg body weight failed to cure the water buffaloes. Cattle were further protected by a single dose of isometamidium chloride administered at 0.5 mg/kg body weight for 6 weeks of this study. On the other hand, isometamidium chloride administered at 1 mg/kg body weight cured transiently 90% of the infected water buffaloes and 10% persisted with a T. congolense infection. It was concluded that the lower dose rates approved by the manufacturers for the two trypanocides treated adequately infected cattle in a low challenge area, but such results were not achieved with the higher dose rates for infected water buffaloes in a high fly challenge area.Resume-L'examen de frottis sanguins de buffles (Bubalus bubalus) provenant d'une region fortement infestee de mouches tse-tse indique un taux d'infection de 51.11%, du a Trypanosoma congolense et T. vivax. Une etude similaire concernant les vaches dans une zone peu infestee montre un taux d'infection de 22.73%, cause par T. congolense uniquement. De l'aceturate de diminazene administre en une dose de 3.5 mg/kg de poids vif soigne l'infection des vaches, alors que les buffles ne sont pas soignes par une dose de 7 mg/kg. Les vaches ont ensuite ete protegees pendant 6 semaines grace a une dose unique de 0.5 mg/kg de chlorure d'isometamidium, tandis que cette meme drogue administree a raison de 1 mg/kg ne soignait transitoirement que 90% des buffles, les 10% restant presentant une infection a T. congolense. On peut done en conclure que les faibles doses recommandees par les fabricants pour chaque trypanocides sont adaptees a des vacnes exposes a de faibles infestations, mais non a des buffles vivant dans des zones lourdement infestees par les glossines.

Susceptibility of a Trypanosoma congolense Isolate of Water-Buffalo Origin to Diminazene Aceturate and Isometamidium Chloride

“…Recently, Berenil at 40 mg/kg failed to cure T. brucei infected cattle in Ethiopia (Abebe, 1987). Trypanosomes infecting water-buffaloes and camels in Africa also seem to resist treatment with the curative doses (deduced as recommended for cattle) of Berenil, Samorin and Ethidium (Gitatha, 1979;Ali et al, 1985, Njau et al, 1986. On the other hand success was obtained with Trypanosoma evansi infected waterbuffaloes in tsetse-free area (Lohr et al, 1985).…”