“The clock is ticking”: high prevalence of tick-borne zoonoses in healthy adults with varying tick-bite exposure in Northwestern Italy

Abstract Tick-borne zoonoses are among the main vector-borne and emerging diseases in Europe. Individuals with chronic high-frequency tick exposure represent sentinel populations for pathogen circulation. In this work, we report the biomolecular prevalence (PCR) and seroprevalence of Babesia divergens , B. microti , Borrelia burgdorferi s.l., Spotted Fever Group (SFG) Rickettsiae , Anaplasmataceae and Tick-borne Encephalitis Virus in a cohort of 144 healthy adults from Northwestern Italy, with varying tick-bite exposure intensity ranging from occasional to > 10 bites/year. Participants were exposed to tick bites through engagement with natural environments, with 65% reporting at least one tick bite per year. Time spent outdoors and checking the body for ticks upon returning home correlated significantly with reported tick-bite frequency. Across all pathogens, biomolecular prevalence was 19%, while seroprevalence was 44%. We detected the highest prevalence for B. divergens (22.2% serology) and B. microti (13.9% serology), followed by SFG Rickettsiae (9.3% PCR, 14.3% serology), A. phagocytophilum (6.9% PCR, 12.5% serology), B. burgdorferi s.l. (0% PCR, 3.5% serology), with no TBEV infections detected. Despite high pathogen exposure, all participants were asymptomatic at sampling, mirroring patterns observed in wildlife host populations where high infection prevalence coexist with subclinical or asymptomatic infections. These findings are consistent with published data from comparable high-exposure cohorts using similar diagnostic methodologies and emphasize the importance of exposure stratification in tick-borne disease epidemiology. This data is relevant to raise awareness in the general public, to inform medical practitioners, and for epidemiological and public health surveillance actions and disease control.