Application of a blocking enzyme-linked immunosorbent assay for serological monitoring of hog cholera (classical swine fever) in Poland.

Between 1990 and 1992, serum samples from 55,478 domestic swine were tested by enzyme-linked immunosorbent assay (ELISA) for the presence of hog cholera virus (HCV) antibodies. The amount of antibody in the sera was expressed as the mean percentage inhibition (PI). For diagnosis, the tested sera were diluted 1:2 and considered positive if the PI was less than 25%. Sera giving PI values in the range of 25-50% were retested against HCV and bovine virus diarrhoea virus (BVDV), by neutralising peroxidase-linked assay. Comparison of the serum titres obtained was used for serological diagnosis of hog cholera; the tested sera were considered negative for hog cholera if the titre for BVDV was higher than that obtained for HCV. All sera with a PI higher than 50% were considered negative for HCV and BVDV. All sera were found to be free of antibodies to HCV. BVDV antibodies were demonstrated in 0.40% of the sera tested in 1990, in 1.80% in 1991 and 1.06% in 1992.