The Role of Wild Boars in the Circulation of Tick-Borne Pathogens: The First Evidence of Rickettsia monacensis Presence

SIMPLE SUMMARY: Wildlife has a major role in the transmission and maintenance of zoonotic agents, as most emerging infectious diseases are of wildlife origin. Among the great variety of wildlife species, wild boars (Sus scrofa) are species with continuously increasing abundance and geographical distribution. Wild boars were suggested as appropriate sentinel species for the distribution and abundance of certain tick species in America and Europe. Therefore, these species may also be suitable sentinel species for screening for tick-borne pathogens. The aim of this study was to evaluate the presence of tick-borne pathogens in wild boars in Romania. A total of 203 blood samples were collected from wild boars (Sus scrofa) from two Transylvanian counties (Cluj, Sălaj) in Romania. Three emerging zoonotic pathogens were identified, Anaplasma phagocytophilum and two Rickettsia species (R. helvetica, R. monacensis) DNA, in the blood of tested animals. These results suggest the involvement of wild boars in the epidemiology of Rickettsia species and A. phagocytophilum. Hence, this species may be used as a sentinel for the general surveillance of these zoonotic pathogens. ABSTRACT: Most wild mammals can serve as hosts both for tick-borne pathogens (TBPs) and for the ticks themselves. Among these, wild boars, due to their large body size, habitat and life span, show high exposure to ticks and TBPs. These species are now one of the widest-ranging mammals in the world, as well as the most widespread suid. Despite the fact that certain local populations have been decimated by African swine fever (ASF), wild boars are still considered overabundant in most parts of the world, including Europe. Altogether, their long-life expectancy, large home ranges including migration, feeding and social behaviors, wide distribution, overabundance and increased chances of interactions with livestock or humans make them suitable sentinel species for general health threats, such as antimicrobial-resistant microorganisms, pollution and ASF geographical distribution, as well as for the distribution and abundance of hard ticks and also for certain TBPs, such as Anaplasma phagocytophilum. The aim of this study was to evaluate the presence of rickettsial agents in wild boars from two counties in Romania. Among 203 blood samples of wild boars (Sus scrofa ssp. attila) collected during 3 (2019–2022) hunting seasons (September–February), 15 were found positive for tick-borne pathogen DNA. Six wild boars were positive for A. phagocytophilum DNA presence and nine for Rickettsia spp. The identified rickettsial species were R. monacensis (six) and R. helvetica (three). No animal was positive either for Borrelia spp., Ehrlichia spp. or Babesia spp. To the best of our knowledge, this is the first report of R. monacensis in European wild boars, thus adding the third species from the SFG Rickettsia, in the epidemiology of which this wild species may have a role as a reservoir host.