Isolation of tick and mosquito-borne arboviruses from ticks sampled from livestock and wild animal hosts in Ijara district, Kenya

Tick-borne viruses infect humans through the bite of infected ticks during opportunistic feeding or through crushing of ticks by hand and, in some instances, through contact with infected viremic animals. The Ijara District, an arid to semiarid region in northern Kenya, is home to a pastoralist community for whom livestock keeping is a way of life. Part of the Ijara District lies within the boundaries of a Kenya Wildlife Service–protected conservation area. Arbovirus activity among mosquitoes, animals, and humans is reported in the region, mainly because prevailing conditions necessitate that people continuously move their animals in search of pasture, bringing them in contact with ongoing arbovirus transmission cycles. To identify the tick-borne viruses circulating among these communities, we analyzed ticks sampled from diverse animal hosts. A total of 10,488 ticks were sampled from both wildlife and livestock hosts and processed in 1520 pools of up to eight ticks per pool. The sampled ticks were classified to species, processed for virus screening by cell culture using Vero cells and RT-PCR (in the case of Hyalomma species), followed by amplicon sequencing. The tick species sampled included Rhipicephalus pulchellus (76.12%), Hyalomma truncatum (8.68%), Amblyomma gemma (5.00%), Amblyomma lepidum (4.34%), and others (5.86%). We isolated and identified Bunyamwera (44), Dugbe (5), Ndumu (2), Semliki forest (25), Thogoto (3), and West Nile (3) virus strains. This observation constitutes a previously unreported detection of mosquito-borne Semliki forest and Bunyamwera viruses in ticks, and association of West Nile virus with A. gemma and Rh. pulchellus ticks. These findings provide additional evidence on the potential role of ticks and associated animals in the circulation of diverse arboviruses in northeastern Kenya, including viruses previously known to be essentially mosquito borne

Characterizing movement patterns of nomadic pastoralists and their exposure to rift valley fever in Kenya

The role of animal movement in spreading infectious diseases is highly recognized by various legislations and institutions such as the World Organisation for Animal Health and the International Animal Health Code. The increased interactions at the nexus of human-animal-ecosystem interface have seen an unprecedented introduction and reintroduction of new zoonotic diseases with high socio-economic impacts such as the COVID-19 pandemic. Rift Valley fever (RVF) is a zoonotic disease that affects both humans and animals and is transmitted by Aedes mosquitoes or through contact with the body fluids of infected animals. This study seeks to characterize movement patterns of pastoralist and how this movement behaviour increases their susceptibility to RVF virus exposure. We levarage on a rapidly growing field of movement ecology to monitor five herds collared from 2013 - 2015 in an RVF endemic semi-arid region in Kenya. The herds were also sampled for RVF antibodies to assess their exposure to RVF virus during the rainy seasons. adehabitatLT package in R was used to analyze the trajectory data whereas the first passage time (FPT) analysis was used to measure the area utilized in grazing. Sedentary herds grazed within 15km radius while migrating herds presented restricted space use patterns during the dry seasons and transient movement during the start and end of the rainy season. Furthermore, RVF virus antibodies were generally low for sedentary herds whereas the migrating herds recorded high levels during their transition periods. This study can be used to identify RVF risk zones for timely and targeted management strategies