Understanding the spatial distribution of tick species and diseases present in Kenya: A systematic review

Introduction: Tick-borne diseases (TBDs) are infections transmitted to humans and animals through the bite of infected ticks or by contact with contaminated bodily fluids. TBDs transmissions like other vector-borne diseases exact a significant public health burden and economic losses in affected communities. Whereas TBDs of animals such as theileriosis and babesiosis dominate in Africa, zoonotic tick infections are also common but underdiagnosed including Tick-borne relapsing fever, Q-fever, and Crimean. Global economic loss due to tick-borne diseases has been estimated at $14,000 - $18,000 million. In Kenya, the occurrence of tick-borne diseases in humans, livestock and wildlife is on the rise, and there is an urgent need to update the distribution maps for these diseases and their tick vectors. This work aims to
understand the spatial distribution of tick species and pathogens associated with them in Kenya.

Methods: We conducted a systematic review to (i) understand the known distribution of tick species and pathogens in Kenya. From the selected studies, we deduced information on tick species, geographical location, and pathogen-detection data and overlaid these in the respective counties.

Results: Several tick species and pathogens were found prevalent in the Southern and Coastal counties of Kenya. These included Amblyomma variegatum for ehrlichiosis and rickettsia africae; Rhipicephalus pulchellus; Rhipicephalus appendiculatus a vector of Theileria parva and Nairobi sheep Disease Virus (NSDV).

Conclusion: By mapping the distribution of ticks and the pathogens, we were able to identify focal areas where TBDs are emerging or re-emerging. This report provides further evidence for the need to prioritise one health in national diseases control policies.

Keywords: Spatial distribution, tick species, tick-borne diseases, Kenya, systematic review