Zoonotic Tick-Borne Pathogens in Temperate and Cold Regions of Europe-A Review on the Prevalence in Domestic Animals

Abstract

Ticks transmit a variety of pathogens affecting both human and animal health. In temperate and cold regions of Europe (Western, Central, Eastern, and Northern Europe), the most relevant zoonotic tick-borne pathogens are tick-borne encephalitis virus (TBEV), Borrelia spp. and Anaplasma phagocytophilum. More rarely, Rickettsia spp., Neoehrlichia mikurensis, and zoonotic Babesia spp. are identified as a cause of human disease. Domestic animals may also be clinically affected by these pathogens, and, furthermore, can be regarded as sentinel hosts for their occurrence in a certain area, or even play a role as reservoirs or amplifying hosts. For example, viraemic ruminants may transmit TBEV to humans via raw milk products. This review summarizes the role of domestic animals, including ruminants, horses, dogs, and cats, in the ecology of TBEV, Borrelia spp., A. phagocytophilum, Rickettsia spp., N. mikurensis, and zoonotic Babesia species. It gives an overview on the (sero-)prevalence of these infectious agents in domestic animals in temperate/cold regions of Europe, based on 148 individual prevalence studies. Meta-analyses of seroprevalence in asymptomatic animals estimated an overall seroprevalence of 2.7% for TBEV, 12.9% for Borrelia burgdorferi sensu lato (s.l.), 16.2% for A. phagocytophilum and 7.4% for Babesia divergens, with a high level of heterogeneity. Subgroup analyses with regard to animal species, diagnostic test, geographical region and decade of sampling were mostly non-significant, with the exception of significantly lower B. burgdorferi s.l. seroprevalences in dogs than in horses and cattle. More surveillance studies employing highly sensitive and specific test methods and including hitherto non-investigated regions are needed to determine if and how global changes in terms of climate, land use, agricultural practices and human behavior impact the frequency of zoonotic tick-borne pathogens in domestic animals.

Keywords: Anaplasma; Babesia; Borrelia; Neoehrlichia mikurensis; Rickettsia; tick-borne diseases; tick-borne encephalitis; vector-borne diseases.

Figure 1

European countries considered in the literature survey on (sero-)prevalence of tick-borne zoonotic diseases in domestic animals. Geographical regions are indicated by different colors: Scandinavia (green), British Isles (yellow), Western continental (blue), and Eastern continental Europe (red).

Figure 2

PRISMA flow-chart detailing the selection process applied during the literature survey.

Figure 3

Animal species and tick-borne pathogens. The size of animal icons corresponds to the number of studies. Symbols indicate the role of each animal species in the ecology of the respective pathogen. Symbols in brackets indicate that this role is uncertain. Borrelia miyamotoi is not shown as no (sero-)prevalence studies regarding this pathogen in domestic animals were retrieved.

Figure 4

Forest plot displaying the results of random-effects meta-analysis of tick-borne encephalitis virus seroprevalence in domestic animals, with subgroup analysis according to animal species. Individual study results are shown as yellow squares, corresponding in size to the weight of the study on the overall prevalence estimate. Error bars indicate 95% confidence intervals (CI). Pooled prevalences are shown as red diamonds and the red dotted vertical line indicates the estimated overall prevalence.

Figure 5

Forest plot displaying the results of random-effects meta-analysis of B. burgdorferi s.l. seroprevalence in domestic animals, with subgroup analysis according to animal species. Individual study results are shown as green squares, corresponding in size to the weight of the study on the overall prevalence estimate. Error bars indicate 95% confidence intervals (CI). Pooled prevalences are shown as red diamonds and the red dotted vertical line indicates the estimated overall prevalence.

Figure 6

Forest plot displaying the results of random-effects meta-analysis of A. phagocytophilum seroprevalence in domestic animals, with subgroup analysis according to animal species. Individual study results are shown as blue squares, corresponding in size to the weight of the study on the overall prevalence estimate. Error bars indicate 95% confidence intervals (CI). Pooled prevalences are shown as red diamonds and the red dotted vertical line indicates the estimated overall prevalence.