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1.
PLoS One ; 13(1): e0190230, 2018.
Article in English | MEDLINE | ID: mdl-29342164

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.


Subject(s)
Dust , Macrophages/microbiology , Mustelidae/microbiology , Mycobacterium bovis/isolation & purification , Animals , Silicon Dioxide
2.
Science ; 354(6313): 744-747, 2016 11 11.
Article in English | MEDLINE | ID: mdl-27846605

ABSTRACT

Leprosy, caused by infection with Mycobacterium leprae or the recently discovered Mycobacterium lepromatosis, was once endemic in humans in the British Isles. Red squirrels in Great Britain (Sciurus vulgaris) have increasingly been observed with leprosy-like lesions on the head and limbs. Using genomics, histopathology, and serology, we found M. lepromatosis in squirrels from England, Ireland, and Scotland, and M. leprae in squirrels from Brownsea Island, England. Infection was detected in overtly diseased and seemingly healthy animals. Phylogenetic comparisons of British and Irish M. lepromatosis with two Mexican strains from humans show that they diverged from a common ancestor around 27,000 years ago, whereas the M. leprae strain is closest to one that circulated in Medieval England. Red squirrels are thus a reservoir for leprosy in the British Isles.


Subject(s)
Disease Reservoirs/microbiology , Leprosy/microbiology , Leprosy/transmission , Mycobacterium/isolation & purification , Sciuridae/microbiology , Animals , Genomics , Humans , Leprosy/epidemiology , Leprosy/genetics , Mexico/epidemiology , Mycobacterium/classification , Mycobacterium/genetics , Mycobacterium leprae/classification , Mycobacterium leprae/genetics , Phylogeny , Polymorphism, Genetic , Protein Domains , Toll-Like Receptor 1/chemistry , Toll-Like Receptor 1/genetics , United Kingdom/epidemiology
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