Pathomorphological changes in the organs of the peripheral immune system in mycobacteriosis of cattle

Abstract

Conducting routine allergy tests of cattle with a simultaneous sample in TB-prone farms is necessary to confirm the stage of the epizootic process. The purpose of the research – to explore the pathomorphological changes in cows upon detection of para allergic reactions during diagnostic testing for tuberculosis. The diagnosis of tuberculosis in animals was performed comprehensively using all methods for tuberculosis control provided for in the guidelines – epidemiological, clinical, allergic, pathological, histomorphological, bacteriological and biological. It allowed establishing that the reactions to tuberculin in cows were of a paraallergic nature, caused by nontuberculous mycobacteria or so-called atypical mycobacteria. It was determined that cows that reacted positively to tuberculin and an atypical mycobacterial allergen and were sent for slaughter for diagnostic purposes did not demonstrate pathological changes characteristic of tuberculosis. However, pathological changes (granulomatous foci, atrophy of lymphoid and epithelioid tissue, hyperplasia of varying intensity and nature, dotted haemorrhages in the cortical zone) were observed in many lymph nodes, including mediastinal, mesenteric, pharyngeal and mandibular lymph nodes, indicating an active infectious process in the body of animals caused by nontuberculous mycobacteria. Therewith, several changes were observed in the lymph nodes during histomorphological examination: development of primary nodules of lymphocytes and reticular tissue in reactive centres, degradation and necrosis of lymphocytes, the establishment of cellular detritus in the centre of the nodules and capsules of epithelioid elements around the nodules, etc., which can be used to confirm the patterns of pathology development and, indirectly, the mechanism of sensitisation of the cow’s body, and therefore the nature of paraallergic reactions in animals. The obtained results are important for the timely detection and identification at the histomorphological level of a complex of changes in the organs and tissues of cows due to the penetration of nontuberculous mycobacteria, which is the key to the successful diagnosis of primary foci of mycobacteriosis and their effective prevention