Comparative study of PCR as a direct assay and ELISA and AGID as indirect assays for the detection of bovine leukaemia virus

The choice of a diagnostic method depends on the characteristics of the her d to be analysed. Two herds with different prevalences of enzootic bovine l eukaemia were chosen to study the concordance between agar gel immunodiffus ion (AGID), enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) methods. PCR, an increasingly used virological method, was p erformed with four sets of primers, amplifying different genomic regions (e nv, pol and tax), from DNA extracted either from peripheral blood monocytes (PBMCs) or milk leucocytes. The highest percentage of positive animals was obtained using PCR performed with DNA extracted from PBMCs using primers w hich amplified either env or pol, followed by PCR using PBMCs and primers w hich hybridized with tax, then ELISA using serum and finally AGID. The resu lts of PCR were more consistent with PBMCs than when milk leucocytes were u sed.