Introduced nilgai (Artiodactyla: Bovidae) intensifies cattle fever tick (Acari: Ixodidae) exposure risk for cattle in the southeast United States

Cattle fever ticks (CFT), Rhipicephalus microplus Canestrini and R. annulatus Say, are the most economically important pests of cattle in the world, and the recent increase of tick incursions in Texas challenges the Cattle Fever Tick Eradication Program (CFTEP). Heightened pressure from growing wildlife host populations along the Texas-Mexico border is a pressing complication for CFT control initiatives. Spatially explicit prediction of wildlife host distribution may provide information essential for allocation of resources by the CFTEP. In this study, we use species distribution models to project the distribution of white-tailed deer (Odocoileus virginianus Zimmerman, Artiodactyla: Cervidae) (WTD) and nilgai (Bosephalus tragocamelus Pallas, Artiodactyla: Bovidae) in the southeastern United States to improve our understanding of cattle exposure to native and introduced wildlife hosts of CFT. Our results reveal that ubiquitous WTD presence in the southeastern US tapers off in the arid west, limiting exposure of US cattle to WTD along the Texas-Mexico border. Additionally, the nilgai distribution model based on the species' native range in India indicates a moderate probability of habitat suitability throughout the southeastern US, and a high probability of habitat suitability in southern and eastern Texas. The expansion of nilgai across their projected suitable habitat increases cattle exposure to CFT wildlife hosts, especially in sensitive, transitional areas along the Texas-Mexico border. We posit that modeling existing wildlife hosts and the potential range expansion of introduced wildlife hosts and overlaying these models with cattle inventory will ultimately help direct efforts to monitor ticks, prevent incursions, and initiate early interventions.