The spread of porcine sarcoptic mange during the fattening period revealed by development of antibodies to Sarcoptes scabiei

Using an indirect ELISA based on a whole body homogenate of Sarcoptes scabiei var vulpes, the development of serum antibodies to S. scabiei var suis during the fattening period was studied in two herds, purchasing fatteners and performing age segregated production systems. All the pigs in one of the herds were treated with ivermectin on the same day within a week after arrival, while no precautions were made to prevent sarcoptic mange in the other herd. In both herds, a transient immune response to S. scabiei was detected in some animals during the early fattening period, reflecting that these pigs had been exposed to S. scabiei before delivery to the fattening units. It also indicated that they had been treated with acaricides close to allocation. The incidence of animals seropositive to S. scabiei was initially low in both herds. The infection spread gradually as indicated by increasing optical densities of antibodies to S. scabiei, especially during the second half of the rearing period. This increase was more pronounced in the herd which had received no prophylactic treatment to sarcoptic mange. The infection with S. scabiei was found to have spread to more animals towards the end of the fattening period in that herd. It was concluded that a single injection with the acaricide on arrival at the fattening farm decreased and delayed the spread of the infection, but did not eradicate the mite infection. The results showed that conventional pigs sold as fatteners at present may be infected with S. scabiei and that precautions aimed at preventing sarcoptic mange therefore, are indicated in fattening herds. In this context, the ELISA employed could be a valuable means of discriminating between S. scabiei var suis infected piglet producing herds and uninfected herds. (C) 1997 Elsevier Science B.V.