Determination of the causes of allergic reactions to tuberculin in cattle

Abstract

The article presents the results of cattle examining in four free from tuberculosis livestock farms during 2020–2021. Samples of biological material were collected and studied in the Laboratory for tuberculosis study of the NSC “IECVM”. The causes of allergic reactions to mycobacterial allergens were established by a comprehensive method. The study was aimed to conduct epizootological monitoring and to determine the causes of positive tuberculin skin tests in cattle in four free from tuberculosis farms. These farms were located in different regions of Ukraine. Epizootological, clinical, allergical, anatomopathological, bacteriological and biological methods were used including a pathological examination of biological material samples (lymph nodes and internal organs), Ziehl–Nielsen staining while bacterioscopy. Samples of biological material were preliminary treated by A. P. Alikaeva’s method and 0.9% solution of cetylpyridinium chloride and inoculated on selective nutrient media for mycobacteria cultivation. As the result of conducted study seven cultures of nontuberculous mycobacteria were isolated from samples of biological material from three cattle herds. It was found that these isolates were represented by four mycobacterial species. There were M. fortuitum, M. phlei, M. smegmatis and M. scrofulaceum. In addition, two cultures of M. avium subsp. paratuberculosis were isolated from one cattle herd. Short-term sensitization to tuberculin for mammals in cattle was caused by atypical mycobacteria in three farms. There were four mycobacteria species; M. smegmatis, M. phlei, M. fortuitum and M. scrofulaceum which persists in the body of animals and does not cause the development of an infectious tuberculosis process. Mycobacterium avium subsp. paratuberculosis (MAP) causes the latent form of an infectious process in the body of cattle and sensitization to tuberculin, as well as pathological lesions in the small intestine. One-month-old rabbits susceptible to MAP can be used as an experimental model for determination of biological properties of epizootic cultures and diagnosis of paratuberculous enteritis. Herds of cattle in which sensitization is triggering by atypical mycobacteria should be considered as free from tuberculosis. Control of welfare and differentiation of nonspecific reactions to tuberculin should be carried out using a simultaneous test with PPD tuberculin for mammals and the allergen from atypical mycobacteria. The study of cattle with a suspicion of paratuberculous enteritis should be carried out by complex method using allergical, serological (CFT, ELISA), pathological, bacteriological and molecular-genetic research methods, as well as using a biological test on one month old rabbits