Epidemiological and diagnostic observations following the elimination of porcine reproductive and respiratory syndrome virus from a breeding herd of pigs by the test and removal protocol

The protocol of test and removal for the elimination of porcine reproductiv e and respiratory syndrome (PRRS) virus was applied to an 825-sow breeding herd. All the adult animals were tested and serum samples analysed by ELISA and polymerase chain reaction (PCR). Eighty-eight animals (10-7 per cent) were removed from the herd and, of these, three were ELISA-positive and Pea -positive, and ss were ELISA-positive and PCR-negative. They tended to be e ither individual sows, or groups of four to six animals housed in adjacent gestation stalls. Four of the ELISA-positive, Pea-negative sows were slaugh tered and PRRS virus nucleic acid was detected in a sample of sternal lymph node from one of them. After the completion of the test and removal protoc ol, the breeding and finishing populations were monitored for it consecutiv e months by ELISA. The 960 samples taken were negative for PRRS virus antib odies.