Endemicity factors and risks of false-positive serological reactions in brucellosis testing of farm animals

The article presents generalized data on the endemicity and epizootology of animal brucellosis. The work was carried out to analyze and summarize the information from the Centralized Research Institute of Veterinary Medicine and Epidemiology of Kharkiv region on research on brucellosis of farm animals. Material samples were examined at the Laboratory of Brucellosis of the National Scientific Center «Institute of Experimental and Clinical Veterinary Medicine» to clarify the diagnosis. The study revealed that brucellosis continues circulating among wildlife populations, especially pigs, despite control efforts. It has been shown that the enzooticity of detecting false-positive reactions in traditional serological tests, namely the dipstick test (DST), agglutination reaction (RA), complement binding reaction (CBR), long-term complement binding reaction (LTCR), and milk ring reaction (MR). The presence of antigenic affinity of the lipopolysaccharide antigen of pathogenic Brucella and other gram-negative bacteria, in particular, Enterobacteriacea, has been confirmed, which causes false positive results that lead to diagnostic errors and unjustified culling of animals. To increase the specificity and reduce the likelihood of false positive results, it is proposed to conduct additional studies of sera at a reduced dose of antigen, which can significantly increase the specificity of RBP as a screening method while maintaining sensitivity. The main risks of occurrence and the presence of pathogen sources, pathways, and mechanisms of transmission of pathogenic Brucella sp. (B. abortus, B. suis, B. melitensis) are identified. Special attention is paid to the aspects of effective diagnostics, which are currently crucial for controlling the spread of this infection. It is shown that the endemic threshold for brucellosis in some regions is a problem related to the complication of serological tests, particularly the risk of false-positive reactions, which are significant obstacles to the diagnosis and prevention of the disease. The authors argue that the results highlight the need to continue research to develop more specific methods and diagnostic tools to control this zoonotic disease effectively