Validation of ELISAs for the detection of antibodies to Sarcoptes scabiei in pigs

An Enzyme-linked ImmunoSorbent Assay (ELISA) was developed for the detectio n of antibodies to Sarcoptes scabiei. This 'Animal Health Service'-ELISA (A HS-ELISA) was compared with a commercial test (Checkit(R) Sarcoptest) using experimental and field sera. The experimental study was a contact infestat ion experiment. Eighty piglets were randomly divided between the experiment al and control group. After introduction of three Sarcoptes scabiei var. su is infested pigs in the experimental group, both groups were monitored by d etermining scratching indices, taking ear scrapings and blood samples in We eks 0, 2, 4, 6, 8, 12 and 16. Four pigs in the control group were immunised with either Dermatophagoides pteronyssinus (Dp) antigens (n = 2), or Acaru s sire (As) antigens (n = 2). In the control group all (non-immunised) pigs were negative in all tests. I n the experimental group only slightly elevated scratching indices were obs erved, with a maximum in Week 8. After 2 weeks for the first time an ear sc raping was positive (2.5%). In Week 8 the highest number of positive ear sc rapings were found (25.0%). Positive results in the Sarcoptest were first o btained in Week 12 (10.5% positive), while eventually 29.0% of the finishin g pigs were positive after 16 weeks. The AHS-ELISA first detected a serolog ical response after 6 weeks (5.0% positives), increasing until after 16 wee ks a large proportion (74.2%) of the finishing pigs were seropositive, maki ng the AHS-ELISA the most sensitive test. In the AHS-ELISA one As-immunised pig remained seronegative, but the other hyper-immunised pigs crossreacted. In the Sarcoptest, only Dp-immunised pig s had elevated Optical Densities (OD's) albeit below the cut-off level. Alt hough hyper-immunisation is not a representation of field conditions, it ca nnot be excluded that the AHS-ELISA is not 100% specific. Field samples were taken from 20 sows in 30 herds, classified as mange-free , suspect, or infested. On a herd level there was high agreement among the ELISAs. Both serological tests were suitable to distinguish mange-free herd s from infested herds.