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 4600 Ixodes ricinus , I. persulcatus and Dermacentor reticulatus tick 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 of D. reticulatus occurrence were found in western and central Latvia, including the Riga region, indicating that the northern border of D. reticulatus in 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 in I. ricinus (34.92%) and I. persulcatus (31.65%) than in D. reticulatus (24.2%). The molecular analysis revealed the presence of tick-borne encephalitis virus, Babesia spp., Borrelia spp., Anaplasma phagocytophilum and Rickettsia spp. Overall, 15 and 7 tick-borne pathogen species were detected in Ixodes spp. and D. reticulatus ticks, respectively. This is the first report of Borrelia miyamotoi in Latvian field-collected ticks. Conclusions This large-scale countrywide study provides a snapshot of the current distribution patterns of Ixodes and Dermacentor ticks in Latvia and gives us a reliable overview of tick-borne pathogens in Latvian field-collected ticks.

BackgroundDifferent tick species are able to transmit different pathogens, and tick-borne diseases are of substantial concern worldwide for both humans and animals. Environmental changes and changes in the range of tick species, including Dermacentor reticulatus in Europe, can affect the spread of zoonotic pathogens. The aim of this study was to investigate the prevalence of the tick-borne pathogens in ticks removed from dogs in Latvia, and to explore possible changes between years 2011 and 2016.ResultsIn 2011, only Ixodes ticks (221 Ixodes ricinus and 22 Ixodes persulcatus) were collected from dogs, while in 2016 tick samples belonged to Ixodes ricinus (360), Ixodes persulcatus (2) and Dermacentor reticulatus (27) species. In total, 35.8 and 40.0% of adult ticks were pathogen-positive in 2011 and 2016, respectively; the difference was not statistically significant (P > 0.05). The molecular analysis indicated the presence of 13 tick-borne microorganisms; the most prevalent pathogen was Rickettsia, followed by Borrelia burgdorferi sensu lato group spirochetes, Anaplasma phagocytophilum and Babesia species. Borrelia miyamotoi was also present. A co-infection with two and three tick-borne pathogens was detected in 7.9 and 7.4% of Ixodes ricinus and Dermacentor reticulatus, respectively. The results of this study confirmed that the spread of novel vectors could bring additional risk of exposure to novel emerging pathogens to pets and their owners, as both Babesia canis and Rickettsia raoultii were shown to be highly associated with Dermacentor reticulatus ticks in Latvia.ConclusionsThis study demonstrates the potential danger from the inadvertent introduction of novel disease pathogens and vectors. Awareness of co-infections and Dermacentor reticulatus-related pathogens needs to be increased.

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