Corbetta, Davide
(2020)
A study of pathological lesions in European badgers (Meles meles) with and without mycobacteriosis in England (northern Edge area).
MVM thesis, University of Nottingham.
Abstract
European badgers (Meles meles) are omnivores members of the family Mustelidae and are widely present in all Europe and the United Kingdom. They are believed to play an important role in the epidemiology of bovine tuberculosis (bTB) in England and several other European countries. Previous studies focused on badgers from cattle bTB endemic areas. European badgers (Meles meles) are also known to be infected by a wide range of other bacterial, viral, protozoal and parasitic diseases.
The aim of this study was to evaluate non-traffic-injury-related macroscopic and histological lesions in road-killed badgers with and without mycobacteriosis from the northern edge of the bTB epidemic, which is considered an area of lower bTB prevalence.
Overall, 607 badger carcasses were collected from six counties in England (northern edge) and necropsied. During post-mortem examination, gross lesions were recorded, and several samples were collected for histopathology, culture and molecular analysis.
A subset of eighty eight (n=88) badgers, 44 positive (M+) microbiologically confirmed mycobacteriosis (whether or not Mycobacterium bovis), and 44 negative (M-), were selected for histopathological examination.
Macroscopically, bite wounds show a trend towards significance in the M+ badgers.
Histologically, in decreasing order of frequency, the most common findings were silica-laden macrophages (85%), granulomas (53%), sarcocystosis (47%), nephritis (31%), portal/periportal hepatitis (26%), and ulcerative dermatitis (18%). M+ badgers had a significantly higher prevalence of granulomas (p < 0.001) and lower prevalence of hepatitis (p = 0.003) than M- badgers. Of the 44 M+ badgers, 31 had M. bovis infection and 13 other mycobacterial infections. Sequencing of rRNA PCR amplicons identified M. nonchromogenicum and M. malmoense in two badgers. M. nonchromogenicum was associated with granulomatous pneumonia and few acid-fast bacilli. M. malmoense was associated with pyogranulomatous dermatitis and abundant acid-fast bacilli.
In conclusion, this study provided a pathological analysis of the most common lesions in road-killed badgers and might set the foundation for further studies of the complex relationship between mycobacteriosis and other diseases in badgers. It also introduced two environmental mycobacteria capable of inducing histological lesions in badgers similar to those caused by M. bovis, a finding relevant to prevalence studies using histology, especially in non-endemic populations, and possibly also to the efficacy of vaccines.
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