Does Mycobacterium tuberculosis var. bovis survival in the environment confound bovine tuberculosis control and eradication? A literature review
Date
2021-02-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Hindawi
Abstract
Bovine tuberculosis (bTB) is one of the globe’s most common, multihost zoonoses and results in substantial socioeconomic costs
for governments, farming industries, and tax payers. Despite decades of surveillance and research, surprisingly, little is known
about the exact mechanisms of transmission. In particular, as a facultative intracellular pathogen, to what extent does survival of
the causative agent, Mycobacterium tuberculosis var. bovis (M. bovis), in the environment constitute an epidemiological risk for
livestock and wildlife? Due largely to the classical pathology of cattle cases, the received wisdom was that bTB was spread by direct
inhalation and exchange of bioaerosols containing droplets laden with bacteria. Other members of the Mycobacterium tuberculosis
complex (MTBC) exhibit differing host ranges, an apparent capacity to persist in environmental fomites, and they favour a range
of different transmission routes. It is possible, therefore, that infection from environmental sources of M. bovis could be a disease
transmission risk. Recent evidence from GPS-collared cattle and badgers in Britain and Ireland suggests that direct transmission
by infectious droplets or aerosols may not be the main mechanism for interspecies transmission, raising the possibility of indirect
transmission involving a contaminated, shared environment. &e possibility that classical pulmonary TB can be simulated and
recapitulated in laboratory animal models by ingestion of contaminated feed is a further intriguing indication of potential
environmental risk. Livestock and wildlife are known to shedM. bovis onto pasture, soil, feedstuffs, water, and other fomites; field
and laboratory studies have indicated that persistence is possible, but variable, under differing environmental conditions. Given
the potential infection risk, it is timely to review the available evidence, experimental approaches, and methodologies that could be
deployed to address this potential blind spot and control point. Although we focus on evidence from Western Europe, the
concepts are widely applicable to other multihost bTB episystems.
Description
Publication history: Accepted - 25 January 2021; Published online - 5 February 2021.
item.page.type
Article
item.page.format
Keywords
Citation
Allen, A. R., Ford, T. and Skuce, R. A. (2021) ‘Does Mycobacterium tuberculosis var. bovis Survival in the Environment Confound Bovine Tuberculosis Control and Eradication? A Literature Review’, Veterinary Medicine International. Edited by D. Morck. Hindawi Limited, 2021, pp. 1–19. doi: 10.1155/2021/8812898.