Pathogenesis of Mycobacterium bovis Infection: the Badger Model As a Paradigm for Understanding Tuberculosis in Animals

Abstract

Tuberculosis in animals is caused principally by infection with Mycobacterium bovis and the potential for transmission of infection to humans is often the fundamental driver for surveillance of disease in livestock and wild animals. However, with such a vast array of species susceptible to infection, it is often extremely difficult to gain a detailed understanding of the pathogenesis of infection--a key component of the epidemiology in all affected species. This is important because the development of disease control strategies in animals is determined chiefly by an understanding of the epidemiology of the disease. The most revealing data from which to formulate theories on pathogenesis are that observed in susceptible hosts infected by natural transmission. These data are gathered from detailed studies of the distribution of gross and histological lesions, and the presence and distribution of infection as determined by highly sensitive bacteriology procedures. The information can also be used to establish the baseline for evaluating experimental model systems. The European badger (Meles meles) is one of a very small number of wild animal hosts where detailed knowledge of the pathogenesis of M. bovis infection has been generated from observations in natural-infected animals. By drawing parallels from other animal species, an experimental badger infection model has also been established where infection of the lower respiratory tract mimics infection and the disease observed in natural-infected badgers. This has facilitated the development of diagnostic tests and testing of vaccines that have the potential to control the disease in badgers. In this review, we highlight the fundamental principles of how detailed knowledge of pathogenesis can be used to evaluate specific intervention strategies, and how the badger model may be a paradigm for understanding pathogenesis of tuberculosis in any affected wild animal species.

Different lesion distribution in calves orally or intratracheally challenged with Mycobacterium bovis: implications for diagnosis

“…As could be expected [ 20 , 38 ], these experimental results suggest that depending on the route of infection the distribution of lesions can vary; that is, after an endotracheal challenge, lesions are more likely to be found in the respiratory tract and associated tissues whereas the digestive tract is the most affected area after an oral challenge. Although the number of animals used was small, these findings are consistent with the results obtained in previous studies where it was stated that after inhalation of M. bovis most lesions appear in the nasopharynx and lower respiratory tract, including the lungs and associated LN and that M. bovis ingestion usually causes lesions in the mesenteric lymph nodes [ 17 , 38 , 39 ].…”

“…There is a general acceptance that the aerogenous transmission is the most frequent one in cattle and lesions are usually found in the respiratory system and associated lymph nodes (LN) [ 17 , 18 ]. This also seems to be the case for natural intra-species transmission in the badger, the principal wild animal reservoir in Ireland and UK [ 20 ]. Lesions can also reach these LN and other tissues or LN of the head region [ 17 , 18 , 21 ] after oral exposure to M .…”

Histopathological and Molecular Investigation of Natural Cases of Bovine Tuberculosis Infection in Cattle

“…A study on the accuracy of histopathological techniques was carried out on limited number of samples from cattle with classical histology features of tuberculosis by Virieux, 2006. The accuracy of histopathologic techniques on large number of samples is available only in cervids (Gormley and Corner, 2018). Varello et al, 2008 claimed that histopathology demonstrated high sensitivity (93.4%) and specificity (92.3%), while ZN sensitivity and specificity were respectively 33.9 and 100 per cent.…”

Risk Factors for the Transmission of Mycobacterium Bovis to Slaughterhouses Workers in Brazzaville, Republic of the Congo

“…Tuberculosis is caused by Mycobacterium tuberculosis in humans resulting in active TB (6) in and M. bovis in cattle with a broader host range for TB in domestic and wild animals (7,8). In addition, M. bovis infects humans, causing zoonotic TB in humans (9).…”