Epidemiology of tick-borne diseases diagnosed in patients in north-eastern Italy, 2015-2022

Background: Ixodes ricinus is the most abundant tick species in Europe and a primary vector for multiple pathogens affecting human and animal health. Over the past 70 years in Europe, including Italy, the geographical distribution of I. ricinus has expanded, increasing the opportunities for tick-human interactions. This observational retrospective study evaluates tick-borne disease (TBD) diagnostic activities conducted from 2015 to 2022 in northeastern Italian hospitals, focusing on areas with significant I. ricinus presence. Methods: Data from over 49,000 human samples that underwent serological screening for Lyme borreliosis (LB), rickettsiosis, anaplasmosis, babesiosis, and tick-borne encephalitis (TBE) were extracted from the information systems of the 4 participating hospitals. Results: Over 52,000 individual serological tests on this population with suspected TBD were performed, primarily for LB (78.4%) and TBE (16.7%), with positivity rates of 14.8% and 21%, respectively, showing significant increasing trend between 2015 and 2022. Male patients predominated (51% for LB and 61% for TBE), especially for IgG positivity, with the 60–69 (LB) and 40–49 (TBE) age groups most affected. Rickettsiosis testing revealed 11.5% positivity with a stable trend, affecting both genders equally, predominately in the 30–39 age group. Anaplasmosis diagnostics (248 tests) showed a maximum positivity rate of ~ 9%, while limited babesiosis testing (64 tests) indicated up to 50% positivity in recent years. Conclusions: The findings underscore the need for enhanced diagnostic tests, vigilant surveillance, and ongoing public education on TBD risks as crucial strategies to mitigate infection risk and reduce the public health impact of TBDs in the northeastern of Italy. Clinical trial number: Not applicable.