| Popis: |
Background: Brucellosis is a zoonosis whose incidence is not declining worldwide despite the global effort to control the disease. Accurate and precise diagnosis is a crucial step in any prophylaxis program but single tests to unequivocally detect animals infected with Brucella spp. are currently unavailable. In Italy, serological diagnosis of bovine brucellosis is performed with two official tests: a rapid agglutination test (i.e., Rose Bengal Plate test, RBPT) and a complement fixation test (CFT) that detect antibodies directed mainly to the smooth lipopolysaccharide (S-LPS). Neither of the two tests is able to avoid the detection of false positive serological reactions (FPSRs) caused by bacteria sharing S-LPS components with Brucella spp. and responsible for the single reactors (SR) phenomenon. An ELISA based on a R strain of Brucella, i.e., Brucella melitensis B115, was employed to measure specific IgG responses in a collection of bovine sera (n=648). Sera were obtained from 180 farms (either officially brucellosis-free or not brucellosis-free) recruited during an extended period of time (2014-2018) and were preliminarily assayed with the official tests by the Italian Reference Centers and then subjected to the ELISA. Results: Negative sera, when subjected to the ELISA, gave an O.D. value below the cutoff (i.e., 0.143); SR sera, i.e. RBPT positive and CFT negative, as well as double positive sera, i.e. RBPT and CFT positive, gave O.D. values that were below the cutoff. All positive sera, i.e. from Brucella-infected animals, were RBPT positive and CFT positive (ICFTU ranging from 20 to 1280) and gave ELISA O.D. values above the cutoff. Conclusions: Neither of the two official tests is able to avoid the detection of FPSRs caused by bacteria sharing S-LPS components with Brucella spp. The B. melitensis B115-based ELISA systematically unravelled all false positive (FP) sera while confirming the diagnosis, so the test employed in the present study may complement official tests to avoid the costly slaughter of FP animals and consequently the economic losses. |
