Modelling the small spatial scale questing abundance of Hyalomma lusitanicum Koch, 1844 (Acari: Ixodidae), vector of Crimean-Congo haemorrhagic fever virus

Abstract

Free-living ticks such as Hyalomma lusitanicum pose a risk to their hosts primarily due to their role as vectors of diseases, with Crimean-Congo haemorrhagic fever (CCHF) being an emerging disease of particular concern in the Iberian Peninsula. This study aims to understand the environmental determinants as well as the host effects that influence the abundance of H. lusitanicum at a small spatial scale. Understanding these factors is essential in identifying areas with a higher risk of tick abundance and, consequently, a greater likelihood of encountering a tick. We conducted 3,840 drags in 32 sampling points in a continental area of the Iberian Peninsula during the peak activity of H. lusitanicum, in May 2021 (1,800 drags in 15 points) and May 2022 (2,040 drags in 17 points). As potential factors influencing H. lusitanicum abundance, we modelled suitability for red deer and we estimated environmental variables that could influence the existence of optimal microhabitats for H. lusitanicum. We modelled H. lusitanicum abundance, performing generalized linear mixed models with a zero-inflated negative binomial distribution, using the abundance per drag as a response variable. We found that a higher local suitability for red deer is the primary determinant of small-scale abundance of H. lusitanicum in our study area. We found other significant factors that affect the abundance of H. lusitanicum which determine the presence of suitable microhabitats, such as adequate vegetation types (suggested by vegetation height), grasslands and mixed vegetation types, and low terrain permeability. This information will significantly aid in the development of more integrated, environmentally friendly, and effective long-term strategies for tick control and the prevention of tick-borne pathogens in regions with climatic and landscape conditions similar to those of our study site.