Diagnosis of swine reproductive failure syndrome by veterinary diagnostic laboratories in the United States from 1987 to 1990

Study on the suitability of sow colostrum for the serological diagnosis of porcine reproductive and respiratory syndrome (PRRS)

Serum and colostrum from 73 sows were collected. The serum samples were tested by Immuno. Peroxidase Monolayer Assay (IPMA) and the corresponding colostrum samples with the indirect Immuno fluorescent Antibody (IFA) technique. All serum positive sows were colostrum positive and all colostrum negative were serum negative. Eight sows only reacted positively in the colostral testing. Compared to the serum standard test the specificity was 82.6% and the sensitivity 100%. The observed agreement between both tests was 89.2%. In addition all serum samples were also tested with the IF test (IFT). Of the eight sows which were negative in the IPMA serum test and positive in the IFA colostrum test, three were found positive when the serum was tested with IFA. Consequently, the observed agreement was higher at 93.2%. After the suitability of colostrum for porcine reproductive and respiratory syndrome (PRRS) diagnosis was demonstrated, 1915 colostrum samples collected from 135 different farms were tested in a comparative study with the IPMA and IFA techniques. Of the 1915 colostrum samples 139 were positive with both IPMA and IFA. With IPMA only, 43 samples were positive compared with 192 samples found positive with the IFA technique. A total of 1541 samples were negative in both tests. The observed agreement between both tests was 87.5%. The quotient of the observed agreement minus chance agreement and the maximum possible agreement beyond chance level (Kappa Quotient) was 0.49. In 90% of the farms that tested IFA positive there was a seroconversion of more than 50% of all colostrum tested. By comparison only 29% of the IPMA positive farms were positive with more than 50%. Based on the epidemiological findings on PRRS it was concluded that the IFA technique indicates a higher sensitivity for the detection of PRRS virus antibodies in sow colostrum. Finally the possible advantages and disadvantages of sow colostrum testing and serum testing are discussed.