Intraspecific Genetic Diversity Among Trypanosomes From Kwale and Marsabit Counties in Kenya

Abstract

African Animal Trypanosomiasis caused by trypanosomes is a great challenge to livestock keeping. The parasites are transmitted biologically by tsetse flies (Glossina spp.) and mechanically by stable flies like Stomoxys spp., horse fly (Tabanus spp.) and camel fly (Hippobosca camelina). While Trypanosoma brucei and T. congolense require cyclical transmission by tsetse flies for maintenance over long periods in a region, their occurrence in parts of tsetse free Northern Kenya, including Marsabit County has been reported. That this could be due to the presence of unknown biological vectors and reservoirs or continuous introduction of trypanosomes due to continuous movement of livestock between tsetse free and infested areas. The aim of the study was to carry out microsatellite genotyping to explore intra-specific genetic diversity between trypanosomes from Shimba Hill, Kwale County tsetse fly belt, and those from Laisamis, Shurr and Ngurunit, tsetse free sites from Marsabit County. Trypanosome DNA was obtained from camel blood, cattle blood and tsetse flies. Molecular detection of trypanosomes was done through the ITS1 PCR diagnostic test. Microsatellite genotyping was done through PCR amplification of seventeen microsatellite loci using fluorescently labeled forward primers. Microsatellite genotyping showed geographical origin based structuring among Trypanozoon isolates. There was clear separation between isolates from the two regions signaling the potential of microsatellite markers as diagnostic markers for T. brucei and T. evansi isolates. Trypanosoma vivax isolates also clustered largely based on sampling location with moderate differentiation (P > 0.5) between the two locations. In addition, the results revealed significant differentiation between isolates from Marsabit and Kwale regions thus revealing that genetic heterogeneity is linked to biological transmission. The results also revealed that T. congolense isolates from xiv Marsabit County are not genetically separated from those from Kwale County. Therefore, these isolates are likely introduced in the region through animal movement. These results have shed new light on the population structure and genetic range of trypanosome species from two distinct ecological settings. There is however need to increase the sample size and area coverage in order to explore the genetic diversity and differentiation between T. congolense isolated from tsetse free areas and those isolated from tsetse endemic area