Tuberculosis in badgers where the bovine tuberculosis epidemic is expanding in cattle in England

Benjamin Michael Connor Swift,Marion Sorley,Elsa Sandoval Barron,Alison Prosser,Catherine Rees,Ranieri Verin,Davide Corbetta,Chris Jewell,Rob Christley,Colman O’Cathail,Jess Phoenix,Llorenç Grau-Roma,Malcolm Bennett,Andy Mitchell

doi:10.1038/s41598-021-00473-6

Abstract

Bovine tuberculosis (bTB) is an important animal health and economic problem for the cattle industry and a potential zoonotic threat. Wild badgers (Meles meles) play a role on its epidemiology in some areas of high prevalence in cattle, particularly in the UK and Republic of Ireland and increasingly in parts of mainland Europe. However, little is known about the involvement of badgers in areas on the spatial edge of the cattle epidemic, where increasing prevalence in cattle is seen. Here we report the findings of a study of found-dead (mainly road-killed) badgers in six counties on the edge of the English epidemic of bTB in cattle. The overall prevalence of Mycobacterium tuberculosis complex (MTC) infection detected in the study area was 51/610 (8.3%, 95% CI 6.4–11%) with the county-level prevalence ranging from 15 to 4–5%. The MTC spoligotypes of recovered from badgers and cattle varied: in the northern part of the study area spoligotype SB0129 predominated in both cattle and badgers, but elsewhere there was a much wider range of spoligotypes found in badgers than in cattle, in which infection was mostly with the regional cattle spoligotype. The low prevalence of MTC in badgers in much of the study area, and, relative to in cattle, the lower density of sampling, make firm conclusions difficult to draw. However, with the exception of Cheshire (north-west of the study area), little evidence was found to link the expansion of the bTB epidemic in cattle in England to widespread badger infection.

Highlights

Bovine tuberculosis is an important animal health and economic problem for the cattle industry and a potential zoonotic threat
M. tuberculosis, the overwhelmingly most frequent cause of human TB and M. microti, which mainly circulates in field voles (Microtus agrestis)[6], are found in Great Britain
Risk, with different surveillance and control measures applied to different areas: the Low Risk Area (LRA), the Edge Area and the High Risk Area (HRA)

Summary

Introduction

Bovine tuberculosis (bTB) is an important animal health and economic problem for the cattle industry and a potential zoonotic threat. The control of TB in cattle in many parts of the world is complicated by the involvement of wildlife species, such as d eer[8] and, in England, Wales, the island of Ireland and increasingly in some other European countries, badgers (Meles meles)[2,3] It is unclear whether or not badgers are technically a reservoir host in the HRA (i.e. a source of infection to cattle—the ‘target’ host—but able to maintain infection without reintroduction from cattle)[2,9], and even less is known about the role of badgers in cattle infection in the Edge Area. The expansion of the cattle epidemic in the Edge Area could be the result of cattle-to-cattle, badger-to-badger, cross species transmission, or, other even less well-understood transmission routes such as through soil and farm waste[10,11,12,13]; and the relative contributions of each potential transmission route, or if they differ between regions in the Edge Area, are unknown

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Conclusion