New approaches to the application of the rose bengal test in post-vaccination diagnostics of brucellosis

Currently, post-vaccination diagnostics of brucellosis is based on two serological methods: Agglutination Test (AT) and Complement Fixation Test (CFT). The weak agglutinogenic properties of the B. abortus 82 vaccine allow carrying out diagnostic tests in the cattle no earlier than 6 months after immunization. The immunodiffusion reaction (IDR) with the O-polysaccharide antigen is used to clarify the epizootic situation in case of suspected brucellosis. If brucellosis is confirmed, a problem surfaces due to with the differentiation of animals and their reaction to the vaccine or infection. Taking into account the simple procedure, high specificity and sensitivity of RBT, we have considered the possibility of using it in the recovery of the cattle in a short period of time after immunization. According to the instruction, the indicators of the RBT test are taken into account only as “positive” and “negative”, so it is not possible to use it as a differentiating test in the immune cattle. At the same time, when taking into account the results of RBT, we paid attention to the correlation with in vitro AT. It has been established that the indicators of the reaction, assessed with crosses, correlate completely with the AT indicators. RBT indicators “+++” and “++++” correspond to AT indicators in levels of 200 IU and above. Moreover, high RBT indicators overlap the CFT indicators at a dilution of 1 : 20 and more IDR indicators. The data obtained substantiate the possibility of using RBT instead of AT and the complicated CFT. The use of RBT turned out to be the most effective in identifying latently sick cattle with positive reactions after they were provoked with a vaccine from strain 82. The data obtained allowed us to conclude that the highly sensitive and easily applied rose Bengal test can be included, instead of AT and CFT, in the system of recovery measures in case of brucellosis in combination with immunodiffusion reaction with O-polysaccharide antigen as an indicator of the presence of brucellosis in the cattle herd.