Influence of environmental temperature and humidity on questing ticks in central Spain

Ticks are important ectoparasites and vectors of the pathogens that cause disease in humans and animals. At a natural reserve in Ciudad Real (Spain), an uncontrollable infestation of wild animals with Hyalomma lusitanicum (Koch) has been reported by some game reserve owners. Many questions about distribution, abundance, and phenology of this tick in this area remain unanswered. The aim of this study was to determine if temperature and relative humidity affect the questing tick's activity in four species of ticks in a meso-Mediterranean area, especially that of H. lusitanicum. Data for tick populations in six selected sampling sites every month, between January 2007 and December 2013 were used. Temperature and humidity values (ground and environmental) were recorded. The sampling effort, the similarity between sites, and the phenology of the species were analyzed. Effects of environmental variables on tick's activity were assessed by general linear models (GLM) whereas the comparative importance of variables was measured by hierarchical variance partitioning. Hyalomma lusitanicum represented 96.3% of the four species of ticks collected. Spring and summer months presented a higher activity of ticks, than autumn and winter months. In general, humidity variables were negatively related to the activity of ticks, whereas temperature variables were positively related. Our results suggest that the highest activity in the area is produced by biological characteristics of H. lusitanicum; being temperature and humidity the most important environmental factors influencing the abundance of this species in the region.