Tick-Borne Pathogens in Companion Animals and Zoonotic Risk in Portugal: A One Health Surveillance Approach

This study aimed to assess the emergence and/or re-emergence of Tick-borne Diseases (TBD) in Portugal by linking the hemoparasite burden in companion animals to vector-borne disease dynamics through a One Health approach. Between 2015 and 2024, 1169 clinically suspected animals with hemoparasite infections, treated at the Hospital Veterinário de Santarém (HVS), underwent serological confirmation for Rickettsia conorii, Babesia canis, Ehrlichia spp., and Haemobartonella spp. A total of 3791 serological tests (3.2 tests per animal) were performed and 437 animals tested positive for at least one of the four hemoparasites under investigation. From 2020 to 2024, tests nearly tripled from 894 to 2883, raising positive cases and prevalence from 29.5% to 39.9%, especially for rickettsiosis and hemobartonellosis, indicating an increased circulation of their vectors. A national vector surveillance initiative identified Hyalomma spp., Rhipicephalus sanguineus, Ixodes ricinus, and Dermacentor sp. as primary tick vectors in Portugal for the hemoparasites mentioned above and for other agents like arbovirus, such as Crimean-Congo Hemorrhagic Fever Virus (CCHFV) and tick-borne encephalitis virus (TBEV). This study found that the vectors responsible for transmitting hemoparasitosis, given the high number of serologically positive cases detected in the HVS, represent an increasing risk for TBD. These findings highlight the relevance of companion animal monitoring as an early-warning component within a One Health surveillance approach.