Abstract:
Trypanosoma vivax is a vector-borne protozoan parasite of livestock endemic to Africa and South America. To
date, fifteen genotypes of the parasite have been described in vertebrate and insect hosts in East Africa. However,
information regarding T. vivax diversity remains limited in many endemic countries in the sub-region, including
Kenya. Such information could deepen insight into the local epidemiology of animal trypanosomiasis in Shimba
Hills, a wildlife area in southeast Kenya where T. vivax is endemic and infects livestock. We employed two-gene
conventional-PCR-sequencing and phylogenetic analysis to characterize T. vivax genotypes in tsetse flies
collected between November 2018 and September 2019 in the wildlife-livestock interface of the Shimba Hills
National Reserve. Phylogenetic analysis of Internal Transcribed Spacer-1 (ITS-1) sequences of T. vivax isolates
confirmed the presence of two T. vivax genotypes in Shimba Hills of which >80% of T. vivax isolates from tsetse
flies clustered within the virulent Tvv4-genotype clade. Tsetse infections with the Tvv4 genotype were also
confirmed based on 18S rRNA gene sequencing. Expanded gene characterization identified three closely related
haplotypes within the Tvv4-clade. The Tvv4-isolates were detected in male and female Glossina pallidipes tsetse
flies, most of which were collected from grasslands and within two kilometres of the Shimba Hills National
Reserve boundary. Considering that T. vivax is the most common trypanosome in the Shimba Hills area and
causes severe clinical conditions in livestock, the Tvv4 genotype reported here for the first time in Kenya contributes
to our understanding of these pathologies. The effectiveness of trypanocidal drugs in the management of
Tvv4 is presently not clearly understood. Therefore, the parasite management in Shimba Hills should focus on
vector control to reduce the density of G. pallidipes, especially in grasslands near the wildlife protectorate.
