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Abstract

BackgroundTrypanosomosis is a major impediment to livestock farming in sub-Saharan Africa and limits the full potential of agricultural development in the 36 countries where it is endemic. In man, sleeping sickness is fatal if untreated and causes severe morbidity. This study was undertaken in western Kenya, an area that is endemic for both human and livestock trypanosomosis. While trypanosomosis in livestock is present at high levels of endemicity, sleeping sickness occurs at low levels over long periods, interspersed with epidemics, underscoring the complexity of the disease epidemiology. In this study, we sought to investigate the prevalence of trypanosomes in small ruminants and pigs, and the potential of these livestock as reservoirs of potentially human-infective trypanosomes. The study was undertaken in 5 villages, to address two key questions: i) are small ruminants and pigs important in the transmission dynamics of trypanosomosis? and ii), do they harbour potentially human infective trypanosomes? Answers to these questions are important in developing strategies for the control of both livestock and human trypanosomosis.ResultsEighty-six animals, representing 21.3% of the 402 sampled in the 5 villages, were detected as positive by PCR using a panel of primers that identify trypanosomes to the level of the species and sub-species. These were categorised as 23 (5.7%) infections of T. vivax, 22 (5.5%) of T. simiae, 21 (5.2%) of the T. congolense clade and 20 (5.0%) of T. brucei ssp. The sheep was more susceptible to trypanosome infection as compared to goats and pigs. The 20 T. brucei positive samples were evaluated by PCR for the presence of the Serum Resistance Associated (SRA) gene, which has been linked to human infectivity in T. b. rhodesiense. Three samples (one pig, one sheep and one goat) were found to have the SRA gene. These results suggest that sheep, goats and pigs, which are kept alongside cattle, may harbour human-infective trypanosomes.ConclusionWe conclude that all livestock kept in this T. b. rhodesiense endemic area acquire natural infections of trypanosomes, and are therefore important in the transmission cycle. Sheep, goats and pigs harbour trypanosomes that are potentially infective to man. Hence, the control of trypanosomosis in these livestock is essential to the success of any strategy to control the disease in man and livestock.

Factors Associated with Acquisition of Human Infective and Animal Infective Trypanosome Infections in Domestic Livestock in Western Kenya

“…Previous observations of a high prevalence of PCR detected trypanosomiasis in small ruminants (20–25%) in Busia District by Ng'ayo and colleagues (2005) were not observed in this study [25]. The results presented here support microscopy and PCR studies in Western Kenya and Eastern Uganda, in which cattle were identified as the most important reservoir of trypanosomiasis, low levels of infection were detected in small ruminants and highly variable infection prevalence depending on sampling sites were seen in pigs (2–20%) [8], [23], [26].…”

Domestic pigs as potential reservoirs of human and animal trypanosomiasis in Northern Tanzania

“…T. b. rhodesiense has been isolated from domestic pigs in western Kenya, on the border of the Ugandan sleeping sickness focus, where G. pallidipes are also present [57]. While data from experimental infections in pigs are available for T. b. gambiense and T. b. brucei from West Africa [33,34], there are gaps regarding T. brucei s. l. pathology and pathogenicity in porcine hosts in East Africa including: the length of time that pigs are able to sustain infections with T. b. brucei or T. b. rhodesiense ; the profile of these infections, in terms of parasitaemia, morbidity and mortality in porcine hosts and the longevity of these hosts within the farming system.…”

Spatial Distribution of Trypanosomes in Cattle From Western Kenya

“…Microscopic analysis of trypanosomes is a cheap and simple technique and is easily employed in the field in the detection of trypanaomiasis. It has been shown to have low sensitivity (23). However, in this study microscopy provided an important pre-screening step and enabled comparative assessment of the results obtained.…”