CONTROL OF SARCOPTES-SCABIEI VAR SUIS WITH IVERMECTIN - INFLUENCE ON SCRATCHING BEHAVIOR OF FATTENING PIGS AND OCCURRENCE OF DERMATITIS AT SLAUGHTER

The behaviour of fattening pigs, the occurrence of erythematous papula r dermatitis in pigs at slaughter and the effects of treatment for man ge with ivermectin at the start of the fattening period were evaluated at ten farms. At each farm, trial pigs were randomly allotted to a co ntrol or a treated group. At the start of the trial, the control group was injected intramuscularly with 5 mg kg(-1) levamisole, and the tre ated group was injected subcutaneously with 300 mu g kg(-1) ivermectin . Skin scrapings, taken from each pig before medication at the start o f the trial, and at slaughter, were examined for presence of sarcoptic mites. Pig behaviour was monitored at 2 week intervals from Week 5 to Week 13 of the trial. Carcasses of trial pigs were inspected for derm atitis at slaughter. Low to moderate Sarcoptes scabiei var. suis infes tations were demonstrated at the start of the trial on five farms (Sfarms). At slaughter, the mean percentage of Sarcoptes-positive pigs p er pen on S+ farms was 34.8% (range 11-60%) for the control group as c ompared with 0.5% (range 0-2.7%) for the ivermectin-treated group (P<0 .01). No S. scabiei was recovered from any pig at any time from the fi ve other farms (mange-free (S-) farms). The low initial levels of mang e in the controls at S+ farms resulted in a consistently high scratchi ng index. Ivermectin treatment resulted in a significantly (P<0.01) lo wer prevalence of scratching, comparable with the prevalence observed at S- farms. High prevalences of generalized dermatitis at slaughter w ere observed in control pigs from all S+ farms. Ivermectin treatment r esulted in much lower prevalences, reflected in a significantly (P<0.0 1) lower grand mean dermatitis index per pen for this group as compare d with the controls. The majority of pigs from both treatment groups a t all S- farms were free of papular lesions. These results indicate th at low levels of sarcoptic mange at the start of fattening, left untre ated, will result in a high prevalence of scratching during the fatten ing period and high prevalences of Sarcoptes and dermatitis at slaught er. Treatment with ivermectin at the start of fattening results in beh aviour and dermatitis prevalences similar to those observed in mange-f ree herds.