OVINE LENTIVIRUS ANTIBODY DETECTION IN SERUM, COLOSTRUM AND MILK USING A RECOMBINANT TRANSMEMBRANE PROTEIN ELISA

An enzyme-linked immunosorbent assay (ELISA) was used to detect antibo dies against ovine lentivirus (OLV) in serum, colostrum, and milk from naturally infected sheep, The assay used OLV recombinant transmembran e envelope protein (rTM) as a test antigen. Matched serum/colostrum an d serum/milk samples were collected at 24 h, 4 weeks (mid-lactation), and 8 weeks (weaning) post-lambing. Among 129 paired samples collected at 24 h post-lambing, there was overall test agreement (concordance) of 82.9% and a kappa value of 0.658 between serum and colostrum rTM EL ISA results. Among 130 mid-lactation samples, the milk ELISA had 100% specificity and 64.9% sensitivity relative to the serum ELISA, there w as concordance of 79.2%, and a kappa value of 0.602, At mid-lactation, the serum a ar gel immunodiffusion test had a a sensitivity of 0.390 and 0.560 relative to the serum and milk rTM ELISAs, respectively, Mat ched serum and milk rTM ELISA results at weaning were very similar to those at mid-lactation, Finally, increased occurrence and severity of subclinical mastitis at weaning was found in ELISA-seropositive compar ed with ELISA-seronegative ewes. Both subclinical mastitis and ewe OLV infection bad a negative impact on lamb growth and weaning weights. C ompared with blood, colostrum and milk are easier and less expensive t o sample and store. These results suggest that rTM ELISA testing of co lostrum and milk could bt used to supplement serologic testing in OLV screening or eradication programs.