Cutaneous hypersensitivity reactions against unfed tick larval extract of Rhipicephalus evertsi in South African Mutton Merino, Namaqua Afrikaner and Dorper sheep

Abstract

Indigenous Namaqua Afrikaner (NA) sheep have been reported to be more resistant to tick infestation than the commercial Dorper and South African Mutton Merino (SAMM) breeds. The aim of this study was to compare cutaneous reactions to unfed tick larval extract (ULE) of Rhipicephalus evertsi in the three breeds to verify if such reactions are related to resistance/susceptibility to tick infestation. ULE was injected in the right ear skin of the animals and induced hypersensitivity reactions in all three breeds. The indigenous NA displayed stronger reactions, immediate and delayed, than the commercial breeds. These results suggest that cell-mediated immune responses are invoked to fight against tick infestation in the NA. It is suggested that the methods used could possibly be refined in future to allow routine evaluation of valuable animals without resorting to more invasive challenge-based strategies in selection candidates.