Abstract:
Shimba Hills is a wildlife area in Kenya and a major focus of tsetse-borne
trypanosomes in East Africa. In Shimba Hills, tsetse-borne trypanosomes
constrain animal health and smallholder livelihoods. However, epidemiological
data to guide hotspot-targeted control of infections are limited. This study
assessed the dynamics of tsetse-borne trypanosome risk in Shimba Hills with
the objective to describe infection hotspots for targeted control. Tsetse flies (n
= 696) collected in field surveys between November 2018 and September 2019
in Shimba Hills were characterized for chronological age and phenotypic sizes
and screened for trypanosome and cattle DNA. Entomological inoculation
rates for trypanosome risk assessment were derived from the product of
fly abundance and molecular rates of vector infection and confirmed cattle
bloodmeals in tsetse flies. In addition, cattle health indicators including
anemia scores were assessed in contemporaneous parasitological surveys
that screened livestock blood samples (n = 1,417) for trypanosome using the
buy-coat technique. Compared with Glossina brevipalpis and G. austeni, G.
pallidipes was the most abundant tsetse fly species in Shimba Hills and had a
wider spatial distribution and greater likelihood for infectious bites on cattle.
The risk of cattle infection was similar along the Shimba Hills human-wildlifelivestock interface and high within one thousand meters of the wildlife reserve
boundary. Trypanosomes in tsetse flies were highly diverse and included
parasites of wild-suids probably acquired from warthogs in Shimba Hills. Age
and phenotypic sizes were similar between tsetse fly populations and did not
aect the probability of infection or cattle bloodmeals in the vectors. Anemia
was more likely in trypanosome-positive cattle whilst parasitological infection
rates in cattle samples maintained a weak relationship with entomological
inoculation rates probably because of the limited time scale of sample
collection. Trypanosome risk in Shimba Hills is high in locations close to the
wildlife reserve and driven by G. pallidipes infectious bites on cattle. Therefore,
trypanosome vector control programmes in the area should be designed
to reduce G. pallidipes abundance and tailored to target sites close to the
wildlife reserve.
