The epidemiology of trypanosomiasis in village livestock in an endemic sleeping sickness area of Western Kenya
A longitudinal epidemiological study of trypanosome infections in domestic livestock was carried out over thirteen months in Busia District, an endemic area of Rhodesian sleeping sickness. It was demonstrated that chemoprophylaxis of domestic livestock with Samorin ® (Rhône Poulenc, France) could virtually eliminate the reservoir of potentially human infective T. brucei spp. infections in domestic animals. In addition to being a potentially useful control measure during outbreaks of sleeping sickness, chemoprophylaxis showed a net economic benefit in the productivity of local cattle. The duration of chemoprophylaxis of domestic livestock with Ethidium ® (Laprovet, France) was much less, as was the economic benefit to livestock production, however the level of challenge was much less in this trial. From the relative preference of tsetse flies for each species of domestic animal and the prevalence and incidence of trypanosome infections, it was concluded that cattle and to a lesser extent pigs were the most important species of domestic livestock in the animal reservoir of Rhodesian sleeping sickness in Busia District. Of the risk factors investigated for cattle acquiring trypanosome infections, the most important was an existing trypanosome infection. The effect on the epidemiology of sleeping sickness of a greater than expected interaction between species of trypanosome infecting cattle offers a possible mechanism for the natural control of the animal reservoir of Rhodesian sleeping sickness. Various parasitological diagnostic techniques for the detection of trypanosome infections in cattle in the field were assessed. Maximum sensitivity of diagnosis and minimum bias in the relative importance of each species of trypanosome was achieved by selecting a suitable combination of diagnostic techniques.