Beware of hitchhiking ticks? Clarifying the variable roles of bird
families in tick movement along migratory routes
Abstract
Ticks are blood-feeding parasites which act as major vectors for various
pathogenic microorganisms affecting both animal and human health. Hard
ticks are known to “hitchhike” on migratory birds as they transit from
breeding to overwintering grounds in spring and autumn, potentially
leading to exchange and establishment of non-endemic tick species in
novel environments. That said, it is not yet clear which migratory bird
taxa play a role in movement of specific tick genera and what influence
migratory season may have. To fill this knowledge gap, we performed a
systematic literature review regarding primary data of ticks moving on
migratory birds within the African-Western Palearctic flyways. In total,
34 studies were found which showed 123 bird species from 37 families
connected to potential movement of 26 tick species representing six
genera (Amblyomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes,
Rhipicephalus). Statistical analysis showed bird families (Ixodes:
Turdidae, Prunellidae; Hyalomma: Turdidae, Strigidae, Muscicapidae,
Motacillidae, Emerizidae) which carried above average number of ticks
were only found for interactions with Hyalomma and Ixodes ticks with
below average estimates found for all tick genera besides Rhipicephalus.
Contrary to expectation, no tick genus, which was found in both
migratory seasons, was estimated to have increased numbers in one season
or the other. In certain cases, tick genera (e.g., Amblyomma) were only
found on birds during spring migration. This pattern could highlight
that the assemblage of ticks present on a bird at capture does not
represent the ticks present at the point of migratory departure,
highlighting an understudied importance of stopover sites to potential
tick introduction or turnover. Taken together, the results presented
here provide guiding information for further analysis into species
specific interactions which will allow for the integration of individual
level variation into understanding the risk of tick movement with
migratory birds and potential for emergent disease.