Elimination of Sarcoptes scabiei in pig herds by single or double administrations of an avermectin

Attempts to eliminate Sarcoptes scabiei var. suis were made in 2 piglet producing herds by intramuscular injections with doramectin (Dectomax, Pfizer inc., New York, USA). No hygienic measures of the environments were undertaken. In herd A, all animals were treated twice at a 14-day interval. Theoretically it should be possible to eliminate the mite with a single injection and therefore the animals in herd B were treated only once. The results were measured by attempts to demonstrate S. scabiei by skin scrapings, by recording skin lesions, by establishing rubbing indexes, and by measuring serum antibodies to S. scabiei. All adult animals greater than 8 months of age and 15 weaned piglets 8-16 weeks of age per herd were investigated prior to treatments and every fourth month for a total of 20 months following administration of the treatments. Live S. scabiei were demonstrated prior to treatments in both herds, but no further. Skin lesion scores, rubbing indexes and serum antibody levels remained low throughout the study. It is possible to eliminate S. scabiei from a herd with one single injection of doramectin. Precautions must be taken to ensure that all animals get a correct dose and that the drug is properly administered.