TREATMENT OF SARCOPTIC MITE INFESTATION AND MITE HYPERSENSITIVITY IN PIGS WITH INJECTABLE DORAMECTIN

Thirty-two pigs were infested experimentally with Sarcoptes scabiei va r suis and allocated randomly to a medicated group (injected intramusc ularly with 300 mu g doramectin/kg) or an unmedicated group (injected intramuscularly with 1 ml saline/33 kg). They were observed daily for 15 minutes for signs of pruritus, and the ear lesions were assessed an d skin scrapings examined for mites on days 7, 14, 21 and 28 after tre atment, In the 16 pigs treated with doramectin the ear lesions resolve d completely within 14 days, no mites were recorded on 15 of them on d ay 7 or on any of them on days 14, 21 and 28; pruritus was greatly red uced from day 7 onwards (range 0 to 0.62 rubbing episodes per pig per day) and papular skin lesions were absent from 15 of the pigs at slaug hter on day 28. In comparison, the ear lesions in the 16 unmedicated p igs failed to resolve in 15 of them. Mites were present on 15 of them at different times during the experiment; the numbers of rubbing episo des ranged from 0.88 to 4.65 per pig per day and all the pigs had papu lar skin lesions at slaughter, In the unmedicated pigs, both the degre e of pruritus and the presence and severity of papular skin lesions at slaughter were greater in those with zero or low mite counts than in those with high mite counts.