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Environmental dust inhalation in the European badger (Meles meles): Systemic distribution of silica-laden macrophages, pathological changes, and association with Mycobacterium bovis infection status.

ABSTRACT: Chronic inhalation of crystalline silica and silicates may lead to severe lung disease in humans, termed silicosis. The disease is an occupational health concern in miners and related professions worldwide. Silicosis is also a strong risk factor for tuberculosis in humans. Due to its subterranean lifestyle, the European badger (Meles meles) is continuously exposed to environmental dust, while this species is also susceptible to tuberculosis, caused by Mycobacterium bovis. To date, a thorough investigation of mineral dust retention and its possible implication as a risk factor for mycobacterial infection in badgers has not been performed. The aims of this retrospective histological study were (1) to describe the systemic tissue distribution of silica-laden macrophages (SLMs) in badgers; (2) to compare the amount of SLMs in tissues of badgers of differing M. bovis infection status, pulmonary SLM burden and age; and (3) to assess whether inflammation was associated with SLMs. We assessed lung, lymph nodes, liver and spleen of 60 wild-caught badgers of known M. bovis infection status for the presence of SLMs using polarizing light microscopy. SLMs were consistently present within the lungs and were widely distributed throughout the lymphatic system. No inflammatory reaction to SLMs, as occurs in human silicosis, was observed in any tissue. Distribution and amount of SLMs were similar between M. bovis positive and negative badgers, and we were not able to show an association between the amount of SLMs and M. bovis infection status. The amount of SLMs within intra- and extrathoracic lymph nodes was positively associated with the amount of pulmonary SLMs, and with age. This is the first report of substantial and systemic tissue retention of mineral dust particles in a mammalian species lacking associated chronic inflammation (i.e. silicosis). We further highlight different pathogenetic mechanisms underlying silicosis and benign SLM accumulations following siliceous dust inhalation.

SUBMITTER: Schoening JM

PROVIDER: S-EPMC5771571 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Environmental dust inhalation in the European badger (Meles meles): Systemic distribution of silica-laden macrophages, pathological changes, and association with Mycobacterium bovis infection status.

Schoening Janne M JM Corner Leigh A L LAL Messam Locksley L McV LLM Cassidy Joseph P JP Wolfe Alan A

PloS one 20180117 1

Chronic inhalation of crystalline silica and silicates may lead to severe lung disease in humans, termed silicosis. The disease is an occupational health concern in miners and related professions worldwide. Silicosis is also a strong risk factor for tuberculosis in humans. Due to its subterranean lifestyle, the European badger (Meles meles) is continuously exposed to environmental dust, while this species is also susceptible to tuberculosis, caused by Mycobacterium bovis. To date, a thorough inv ...[more]

PMID: 29342164

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Project description:Tuberculosis (TB) vaccination could be used as a key part of integrated strategies for the disease's control if an effective and safe vaccine under field conditions is obtained. Recent studies in Spain have evaluated the protective efficacy of two oral vaccines against experimental challenge with live intra-bronchial Mycobacterium bovis in captive badgers: the live-attenuated M. bovis BCG vaccine (Danish strain) and a heat-inactivated M. bovis (HIMB) vaccine. With the objective of increasing the knowledge of the cellular development progress of infection and generating further tools to discriminate between mild and severe TB lesions between and within animals, the immunopathology of tuberculous lesions was studied to characterize the local immune response (cell type profile) within lung granulomas from control (non-vaccinated), BCG vaccinated and HIMB-vaccinated experimentally infected badgers with M. bovis. Four immunohistochemical protocols, for the specific detection of macrophages, T lymphocytes, B lymphocytes and plasma cells within TB granulomas in formalin fixed sections of the right middle lung lobe (lobe targeted for the M. bovis delivery), were performed. Immunolabelled sections were scanned and five randomly selected areas were analyzed with digital image analysis software. The results were expressed as the proportion of the positively immunolabelled area within the total area of the selected site. Data was analyzed using the statistical analysis software (SAS). In the three treatment groups, macrophages were the most abundant inflammatory cells within the granulomas, followed by B lymphocytes and plasma cells. T lymphocyes were absent in those granulomas. This would suggest a predominance of a non-specific innate response mediated by phagocytic cells over an adaptative humoral immune response. The proportion of macrophages and plasma cells was higher in BCG and HIMB-vaccinated badgers, respectively, suggesting the establishment of an adaptative humoral response in HIMB-vaccinated badgers. The lower bacterial load at the lung level, as well as the volume of lesions in lungs using magnetic resonance imaging in badgers with the HIMB vaccine in relation with local immune response presented, must be highlighted, since it would be an advantage in favor of its use under field conditions in terms of reducing TB transmission and environmental contamination.

Dataset Information

Environmental dust inhalation in the European badger (Meles meles): Systemic distribution of silica-laden macrophages, pathological changes, and association with Mycobacterium bovis infection status.

Publications

Environmental dust inhalation in the European badger (Meles meles): Systemic distribution of silica-laden macrophages, pathological changes, and association with Mycobacterium bovis infection status.

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