Trypanosomiasis in Kenya is no longer viewed as a public health issue, as only
sporadic sleeping sickness cases are reported from historic foci such as Busia.
Trypanosomiasis is thus mainly perceived as a constraint on livestock production.
The responsibility for tsetse and trypanosomiasis control in Kenya has therefore
increasingly shifted from the state to individual livestock owners; this drastically
reduced the scale of control approaches. This thesis examines the epidemiology of
both animal infective and zoonotic trypanosome species in a range of domestic
livestock at the micro-scale, in Busia, Kenya. The work is based on a unique crosssectional
census data set of the entire livestock population in two study sites in Busia,
employing sensitive molecular tools (PCR) to detect trypanosome infections.
Cattle were the largest reservoir of trypanosomes with an infection prevalence of
20.1%, followed by pigs (11.5%). A low prevalence of infection was detected in
small ruminants (3.3%). Human infective trypanosomes (71 b. rhodesiense) were
detected at a low prevalence in cattle (1.5%) and pigs (2.9%). Key clinical signs for
trypanosomiasis infection (anaemia & poor body condition) were only observed in a
minority of infected cattle (<20%). Confinement of livestock to the homesteads,
instead of grazing in communal grounds and watering at the river did not provide
protection from trypanosome infections. An investigation of the micro-geographic
variation in the distribution of trypanosome infections over the study population,
revealed significant clustering in one of the two study sites. However, there was no
significant effect of distance to water features on trypanosomiasis risk at the herd
level. A convenience sampling protocol was shown to give a good estimate of overall
trypanosomiasis in cattle, but failed to detect the low prevalence of T. b. rhodesiense.
The sustainability of small-scale trypanosomiasis control based on trypanocide
treatment of visibly diseased cattle is appraised and the feasibility of additional
vector control is discussed. Furthermore, the potential human health implications of a
livestock reservoir of T. b. rhodesiense to the local population are examined.