An insight into the histopathology caused by the tick Rhipicephalus sanguineus (Acarina: Ixodidae) in the skin of previously infested, vaccinated or tick-bite naive dogs, guinea pigs and hamsters

Abstract

Dogs', guinea pigs' and hamsters’ local skin reaction to the attachment and feeding of the tick Rhipicephalus sanguineus were analysed under light microscopy. The hosts were either tick-bite naive, previously infested or vaccinated with crude unfed adult tick extract. Biopsies were taken at the end of each infestation. Changes common to every host, regardless of experimental group, included presence of tick or its mouthparts embedded in a cone of cementum at the surface of the skin, epidermal hyperplasia, hyperkeratosis and acanthosis, edema and copious inflammatory cell infiltration in the dermis, underneath the tick attachment site. Dogs in all experimental groups reacted with an almost exclusive PMN neutrophil accumulation, while guinea pigs showed a predominantly mononuclear cell infiltration in every experimental group. Hamsters suffering first infestations had a mainly neutrophilic infiltration, showed a predominantly mononuclear cell infiltration in response to multiple infestations, and when previously vaccinated this host had a predominantly eosinophilic infiltration. The persistence of PMN neutrophils in dogs suggest a control of the local immune inflammatory response by the tick. The predominantly eosinophilic infiltration in previously vaccinated hamsters might indicate that different immune mechanisms were triggered by infestation and vaccination.