Large-scale countrywide screening for tick-borne pathogens in field-collected ticks in Latvia during 2017-2019

Background: Tick-borne diseases are of substantial concern worldwide in both humans and animals. Several hard tick species are of medical and veterinary interest in Europe, and changes in the range of tick species can affect the spread of zoonotic pathogens. The aim of the present study was to map the current prevalence and distribution pattern of ticks and related tick-borne pathogens in Latvia, a Baltic state in northern Europe. Methods: Nearly 4600Ixodes ricinus,I. persulcatusandDermacentor reticulatustick samples were collected in all regions of Latvia during 2017-2019 and were screened by molecular methods to reveal the prevalence and distribution pattern of a wide spectrum of tick-borne pathogens. Results: New localities ofD. reticulatusoccurrence were found in western and central Latvia, including the Riga region, indicating that the northern border ofD. reticulatusin Europe has moved farther to the north. Among the analyzed ticks, 33.42% carried at least one tick-borne pathogen, and 5.55% of tick samples were positive for two or three pathogens. A higher overall prevalence of tick-borne pathogens was observed inI. ricinus(34.92%) andI. persulcatus(31.65%) than inD. reticulatus(24.2%). The molecular analysis revealed the presence of tick-borne encephalitis virus,Babesiaspp.,Borreliaspp.,Anaplasma phagocytophilumandRickettsiaspp. Overall, 15 and 7 tick-borne pathogen species were detected inIxodesspp. andD. reticulatusticks, respectively. This is the first report ofBorrelia miyamotoiin Latvian field-collected ticks. Conclusions: This large-scale countrywide study provides a snapshot of the current distribution patterns ofIxodesandDermacentorticks in Latvia and gives us a reliable overview of tick-borne pathogens in Latvian field-collected ticks.