Abstract
Abstract: The possibility of using indirect hemagglutination assay (IHA) with milk (IHA/m) to differentiate post-infectious antibodies from post-vaccination ones in cows immunized with the Brucella abortus 82 was studied. Anti-Brucella antibodies by IHA/m were detected in the milk of all lactating animals (n=20) culled on the results of tube agglutination test (AT) and/or complement fixation test (CFT), while the milk ring test (MRT) were negative in 20% of cases. IHA/m, as well as IHA with blood serum (IHA/s), confirmed brucellosis in cows with AT- and/or CFT- negative or questionable results. The correlation coefficient between the results of the two IHA variants was very high (r = 793), and the hemagglutinin titers in the blood serum were significantly higher - 1:760 (+13.3%; -11.7%) than in AT-1:260 (+8.7%;-8.0%) (P≤0.01). Vaccination of cows caused increased production of complement-fixing, agglutinating and precipitating antibodies, which tended to weaken during observation of the animals: 30, 60 and 90 days post-vaccination (p.v.). By the end of the experiment, all vaccinated animals showed questionable AT; positive RID/O-PS and IHA/s were noted in 10% and 20% of cases, respectively. However, complement-fixing antibodies remained at diagnostic values in all animals until the end of the experiment. Despite the intense antibody immune response to the vaccine injection, there were no Brucella-specific agglutinins detected by IHA/m and MRT in the milk of cows even on the 30th day p.v. The results show the need for further study on a large population to determine the diagnostic value of IHA/m for differentiating infected from vaccinated animals.