Attempts to immunize sheep against the scab mite, Psoroptes ovis

Summary Adult Psoroptes ovis were successively extracted in saline, 1% Tween, 1% Triton and 8 m urea +0·1% CHAPS. The Triton extract was separated into fractions which did or did not bind to ConA lectin. Using QuilA as adjuvant, both Triton fractions and the saline, Tween and urea extracts were tested separately as candidate protective antigens against a P. ovis challenge infestation in sheep. All induced circulating antibody responses, but the saline and Tween extracts also stimulated significant protective effects in those sheep which developed active disease. Compared to control sheep injected with adjuvant only, these immunized animals had more than two and seven‐fold reductions in mean lesion areas and mite numbers, respectively.