A Systematic Review of the Distribution of Tick-Borne Pathogens in Wild Animals and Their Ticks in the Mediterranean Rim between 2000 and 2021

Abstract

Tick-borne pathogens (TBPs) can be divided into three groups: bacteria, parasites, and viruses. They are transmitted by a wide range of tick species and cause a variety of human, animal, and zoonotic diseases. A total of 148 publications were found on tick-borne pathogens in wild animals, reporting on 85 species of pathogens from 35 tick species and 17 wild animal hosts between 2000 and February 2021. The main TBPs reported were of bacterial origin, including Anaplasma spp. and Rickettsia spp. A total of 72.2% of the TBPs came from infected ticks collected from wild animals. The main tick genus positive for TBPs was Ixodes. This genus was mainly reported in Western Europe, which was the focus of most of the publications (66.9%). It was followed by the Hyalomma genus, which was mainly reported in other areas of the Mediterranean Rim. These TBPs and TBP-positive tick genera were reported to have come from a total of 17 wild animal hosts. The main hosts reported were game mammals such as red deer and wild boars, but small vertebrates such as birds and rodents were also found to be infected. Of the 148 publications, 12.8% investigated publications on Mediterranean islands, and 36.8% of all the TBPs were reported in seven tick genera and 11 wild animal hosts there. The main TBP-positive wild animals and tick genera reported on these islands were birds and Hyalomma spp. Despite the small percentage of publications focusing on ticks, they reveal the importance of islands when monitoring TBPs in wild animals. This is especially true for wild birds, which may disseminate their ticks and TBPs along their migration path.

Keywords: Mediterranean Rim; TBP; island; tick; wild animal.

Figure 1

Methodology diagram for the bibliographic research in keeping with the PRISMA 2009 flow chart according to Moher et al., 2015.

Figure 2

Number of publications through the years (2000–February 2021). The total number is indicated in red, and the other colored lines indicate the number of publications according to each detection method used (serology, microscopy, or molecular biology).

Figure 3

Distribution of main TBP-positive engorged tick species in Mediterranean Rim countries (n = number of TBP-positive engorged tick species by country).

Figure 4

(A) Map of publications per country and Mediterranean area (n = number of publications), (B) of the main wild animal hosts, (C) of the main TBPs in the four Mediterranean Rim areas, (D) and main wild animal hosts, genera of TBP-positive ticks, and TBPs on the western and eastern Mediterranean islands.