Observations on the trypanosomosis problem outside the tsetse belts of Sudan.

Entomological and trypanosomosis surveys were conducted in the Blue Nile area between Admazien and Khartoum. The surveys showed the area to be tsetse free. The only species of trypanosome found to infect cattle in this study was Trypanosoma vivax, which infected some of the local cattle that had no history of entering tsetse belts. The prevalence of disease varied with the season. High disease prevalence coincided with the periods when tabanid and stomoxy flies were abundant. The study showed that the months when biting flies were most numerous coincided with trypanosomosis outbreaks, but even minimal numbers of these flies may cause the cycle of mechanical transmission to continue in stable enzootic conditions.