Diversity of ticks on trails in Asturias (northwest Spain): big differences depending on the study area

Abstract

BACKGROUND: Located on the northern coast of Spain, Asturias offers travellers and residents awe-inspiring landscapes that can be enjoyed through its extensive network of hiking, biking and horseback riding trails. Nevertheless, due to its climatic and faunistic conditions, this region is also favourable for the presence of ticks, especially the Ixodes ricinus species, considered the main vector of Lyme borreliosis, a disease endemic to the area. OBJECTIVES: Our aim is to assess the public health risk of tick bites on the busiest hiking trails of this autonomous region within the framework of a vector surveillance program for the Department of Health of Asturias. METHODS: Between March 2023 and November 2024, a total of 1,477 questing ticks (96 larvae, 1,013 nymphs and 368 adults) were collected by drag sampling on 44 trails in Asturias. Collected ticks were identified based on morphological criteria and stored in 70 % ethanol for later analyses of pathogen communities. RESULTS: Seven tick species of the genera Ixodes, Haemaphysalis, Dermacentor and Rhipicephalus were identified. I. ricinus accounted for 64.7% (238/368) and D. reticulatus for 22.5% (83/368) of adult ticks identified, whereas other species as Haemaphysalis inermis, Dermacentor marginatus, Rhipicephalus bursa, H. concinna and H. punctata accounted for 6.0%, 4.3%, 1.1%, 0.8% and 0.5% respectively. CONCLUSIONS: As expected from previous studies in the region, I. ricinus was the most abundant species overall. However, on the trails closest to large population centers and during the coldest months of the year, D. reticulatus was the most abundant species. Although the analyses to detect pathogens in the collected ticks is still pending, in previous studies we found, a prevalence of 7.8% for Rickettsia spp. and 3.7% for B. burgdorferi s.l. in vegetation ticks. Therefore, we can consider that these pathogens are among the main risks for trail users.