What is the risk of infection from a tick bite in Spain?

Introduction: The development of parameters to estimate the risk of transmission of infections is one of the objectives of entomological surveillance, included in the National Plan for the Prevention, Surveillance and Control of Vector-Borne Diseases. This study aims to assess the utility of the infection prevalence (IP) of Rickettsia spp., Borrelia burgdorferi, and Crimean-Congo haemorrhagic fever virus (CCHFV) in ticks in Spain, as an indicator of the risk of infection from a tick bite and for temporal and geographical comparisons.

Methods: The IP and its 95% confidence interval (95% CI) were calculated for the different microorganism-tick pairs, using data published until April 2024, obtained through a systematic literature review. Studies that included pathogen detection using molecular methods in ticks collected from vegetation (questing ticks) were selected.

Results: 581 articles were reviewed, and 20 were selected. The IP of Rickettsia spp. in Dermacentor marginatus was 84.4%, in D. reticulatus 45.9%, and in Rhipicephalus sanguineus 21.2%, with some Rickettsia species causing DEBONEL (R. raoultii and R. slovaca) and MSF-like illness (R. massiliae) being the most frequent. The IP of Borrelia burgdorferi sensu lato in Ixodes ricinus was 5.9%. The IP of CCHFV in Hyalomma spp was 0.3%.

Conclusions: The IP varies for each pathogen-tick pair, from very high for Rickettsia in Dermacentor, to relatively low for Borrelia in Ixodes and CCHFV in Hyalomma. The infection prevalence in ticks can be a useful indicator, along with other factors, for estimating the risk of infection from a tick bite and conducting population risk assessments in Spain.