Ticks and Tick-Borne Pathogens Encountered by Dogs and Cats: A North European Perspective

Abstract

Climate change is increasing the worldwide burden of tick-borne diseases (TBDs). Dramatic increases in human cases of borreliosis have been reported during the past few decades, including from Finland, located in North Europe. As human exposure to ticks carrying pathogens is increasing, so likely is exposure of dogs and cats. However, feline or canine TBD cases are not notifiable. Likewise, no combined databases of cases exist in Finland, hindering assessment of related trends. Here, we utilize crowdsourced tick samples to reveal how commonly and to which species of TBPs dogs and cats are exposed locally. Borrelia spp., Rickettsia spp., Anaplasma phagocytophilum, Neoehrlichia mikurensis, Babesia spp., Francisella tularensis, Bartonella spp., and tick-borne encephalitis virus (TBEV) were screened using qPCR from a total of 3697 Ixodes ricinus and 2355 Ixodes persulcatus removed from dogs and cats. Furthermore, the spatial occurrence of the screened pathogens was mapped on the national level. An overwhelming majority (99%) of ticks removed from dogs and cats were adults. Prevalence rates in adult ticks were 26.2% for Borrelia, 9.3% for Rickettsia, 1.1% for A. phagocytophilum, 1.1% for TBEV, 0.6% for N. mikurensis, and 0.4% for Babesia. Bartonella and F. tularensis were not detected. All detected pathogens were observed from ticks removed from both host species and both tick species. Borrelia and Rickettsia were detected from every Finnish administrative region, whereas the occurrence of other pathogens was sporadic. This study shows that dogs and cats in Finland are frequently exposed to ticks and TBPs, highlighting that methods for protecting the animals from ticks should be further promoted. The ticks removed from dogs and cats were almost exclusively adult ticks, despite juvenile life stages being more numerous in nature. This raises questions about the numbers of juvenile ticks successfully feeding on dogs and cats and how dogs and cats are thus potentially contributing to tick population upkeep.