Mycobacteriosis of cattle: pathomorphological changes in organs of the peripheral immune system. Medico-epidemiology significance

Abstract

The paper presents the results of histomorphological studies of materials from cows that reacted positively to tuberculin and AAM (allergen of atypical mycobacteria) during planned allergy studies of cattle by simultaneous sampling, in one of the tuberculosis-free farms of the Volyn region.

Diagnosis of animal tuberculosis in the farm is carried out comprehensively using all the methods prescribed by the instructions for the fight against tuberculosis - epizootological, clinical, allergic, patho-anatomical, histomorphological, bacteriological and biological. Thanks to complex diagnostics, we were able to establish that reactions to tuberculin in cows were of a paraallergic nature, caused by non-tuberculous mycobacteria (NTMB) or so-called atypical mycobacteria (AMB).

It was established that cows that reacted positively to tuberculin and AAM and were slaughtered for diagnostic purposes did not have pathological changes characteristic of tuberculosis. However, pathological changes (granulomatous foci, atrophy of lymphoid and growth of epithelioid tissue, hyperplasia of various intensity and character, spotty hemorrhages in the cortical zone) were detected in most lymph nodes, in particular, mediastinal, mesenteric, nasopharyngeal, and submandibular, which indicate an active infectious process in animal organism caused by NTBM.

Likewise, at the histomorphological level, a number of changes were found in lymph nodes (formation of primary nodules from lymphocytes and reticular tissue in reactive centers, degradation and necrosis of lymphocytes, formation of cellular detritus in the center of nodules and capsules from epithelioid elements around nodules, etc.), which confirm the regularity of the development of the detected pathological anatomical changes and indirectly indicate the mechanism of sensitization of the body of cows, and therefore the nature of paraallergic reactions in animals.

The detected pathomorphological changes in the lymph nodes and large intestine, as well as the release of acid-resistant AMB (M. fortuitum, M. scrofulaceum, Nocardia spp.) confirm the objective functioning of the epizootic process of mycobacteria in the herd of dairy cows. Milk obtained from AMB-infected cows may be a source of potential biohazards to human health through dairy foods and thus constitute a medico-epidemiological problem.