Abstract:
Rodents are recognised as important hosts of ixodid ticks and as reservoirs of tick-borne
pathogens across the world. Sympatric insectivores are usually inconspicuous and often
overlooked as hosts of ticks and reservoirs of disease. Elephant shrews or sengis of the
order Macroscelidea are small insectivores that often occur in sympatry with rodents in
southern Africa. Sengis are invariably parasitised by large numbers of immature ticks while
sympatric rodents are infested with very few. The reason for the difference in tick parasitism
rates between these hosts is unknown. While a number of mechanisms are possible,
we hypothesised that certain tick species exhibit “true host specificity” and as such would
only attach and feed successfully on their preferred host or a very closely related host
species. To investigate this, we conducted feeding experiments using two economically
important tick species, the brown paralysis tick, Rhipicephalus warburtoni and the Karoo
paralysis tick, Ixodes rubicundus and two sympatric small mammal species as potential
hosts, the eastern rock sengi, Elephantulus myurus and the Namaqua rock mouse, Micaelamys
namaquensis. Ticks attached and fed readily on E. myurus, but did not attach or feed
successfully on M. namaquensis suggesting that these ticks exhibit true host specificity. We
suggest that a kairomonal cue originating from the odour of E. myurus may stimulate the
attachment and feeding of these ticks and that they further possess immunosuppressive
mechanisms specific to E. myurus, allowing them to feed on this host species but not on
M. namaquensis. This study highlights the importance of small mammalian insectivores as
potential hosts of ixodid tick species and hence their potential as reservoirs of tick-borne
pathogens.
