Abstract
Current serological tools (complement fixation test -CFT- or Rose-Bengal test -RBT-) do not offer satisfactory results for swine brucellosis diagnosis. A recently developed indirect ELISA (iELISA) for the detection of anti- B. suis antibodies, based on a combination of two antigens derived from both rough (r-) and smooth (s-)Brucella LPS, was shown to limit false positive serological reactions (FPSR). Based on the same concept, the ID Screen® Brucella suis Indirect is a double- well iELISA using smooth and rough extracts as antigens. Test performance was assessed by testing 3 groups of swine sera (origin: France): i) positive reactors from infected herds (n=286; positive in CFT and RBT) ii) FPRS from free herds (n=202; positive in RBT) iii) negative reactors from free herds (n=720, RBT negative). Results were expressed as S/Pvalues and interpreted as per manufacturer’s instructions. Animals are considered to be infected with B. suis when positive with both the s- and r-LPS antigens. FPRS should only react on the s-LPS, and are considered as negative. A Receiver Operating Characteristic (ROC) curve analysis was performed. Measured sensitivity was 72.7% (IC95% 67.5-77.9%, n=286); specificity was 99.9% (IC95% 99.6-100%, n=720). Out of 202 FPRS tested, 197 were found negative with the new ELISA, drastically reducing the false positive reactors rate: measured specificity on FPRS was 97.5% (IC95% 95.3-99.7%, n=202). Different cut- off values were tested; it is possible to increase the B. suis sensitivity without significantly affecting specificity. Increasing sensitivity could be of interest when testing herds where the presence B. suis has been already confirmed. To conclude, this new iELISA could improve surveillance and control programs of porcine brucellosis by reducing the impact of FPRS in herds, historically negative for Brucella infections.
