Modelling tick abundance and environmental suitability in meso-Mediterranean landscapes for the prevention of tick-borne diseases

Ticks are ectoparasites of high sanitary relevance because they host and transmit a multitude of pathogens to vertebrates. A comprehensive understanding of their distribution and abundance is essential for the implementation of effective measures to prevent tick-borne pathogen transmission and tick-borne disease occurrence. Therefore, this study aimed to identify the most environmentally suitable areas and the spatial variation in abundance of exophilic ticks in Castilla-La Mancha (CLM), a highly environmentally diverse meso-Mediterranean region in south-central Spain, where Crimean-Congo haemorrhagic fever is an emerging disease. For modelling tick questing abundance, we performed blanket dragging samplings in 20 sites of CLM from 2019 to 2022. For the environmental suitability modelling, the former survey was complemented with tick presence data from various sources. Along 513 blanket-dragging transects of 100 to 1,200 m long (median: 550 m), we collected 1,260 adult ticks of four species: Hyalomma lusitanicum, Rhipicephalus bursa, Dermacentor marginatus, and Haemaphysalis punctata. A specific questing abundance index that was estimated for each species and presence data at a 1x1km spatial scale was modelled using generalised linear mixed effects models and MaxEnt, respectively, with selected climatic and habitat variables. We observed that the relevant environmental predictors of tick abundance and suitability showed certain differences and similarities among species. However, in all cases, specific climatic and habitat factors were relevant predictors. The geographical patterns of abundance and suitability also differed among species, with D. marginatus and R. bursa showing more widespread patterns of both abundance and suitability. In contrast, H. lusitanicum displayed higher predicted abundance and environmental suitability in the west of the region, whereas eastern CLM was more suited for the presence and higher abundance of H. punctata. This study enhances our understanding of tick ecology in central Spain, offering critical insights for early warning systems and tick-borne disease prevention.Author summary: Ticks can transmit serious diseases to humans and animals, making them a public health concern. In this study, we wanted to understand where different types of ticks are most likely to be found and how common they are in Castilla-La Mancha, a region in central Spain. We collected ticks in the field over several years and also gathered data from other sources. Then, we used computer models to predict which areas have the best environmental conditions for ticks to live and where their numbers are likely to be highest. We found that different tick species prefer different parts of the region and different types of environments. Our results help show where the risk of tick bites and tick-borne diseases may be greater. This knowledge can help public health authorities and other stakeholders take preventive actions, such as warning the public or monitoring specific areas more closely.