Cutaneous hypersensitivity reactions to Psoroptes ovis and Der p 1 in sheep previously infested with P. ovis—the sheep scab mite

We have previously shown that infestation with Psoroptes ovis induces an IgE response and intense tissue eosinophilia, typical of a Type I hypersensitivity response [Parasite Immunol. 22 (2000) 407]. Intradermal tests (IDSTs) suggest that there are also delayed and Arthus-type responses to this parasite. In order to study the nature of ovine cutaneous reactions to P. ovis, naı̈ve controls and experimentally infested sheep (n=5) were challenged intradermally with mite antigen. Challenge elicited immediate (P<0.001) and delayed (P<0.005) wheal reactions in sensitised sheep. At 6 (P<0.02) and 30 h (P<0.001) the predominant infiltrating cells were eosinophils. To explore the role of circulating antibodies, naı̈ve sheep (n=5) were subjected to Prausnitz–Kustner (PK) tests. These elicited immediate (P<0.02) but not delayed wheal reactions. At 6 h eosinophils (P<0.001) dominated the infiltrate. These results suggest that P. ovis allergens provoke an IgE-dependent immediate and late phase response and a cell-mediated eosinophil-rich delayed-type hypersensitivity response (ER-DTH).