Bovine Tuberculosis in Britain and Ireland – A Perfect Storm? the Confluence of Potential Ecological and Epidemiological Impediments to Controlling a Chronic Infectious Disease

Abstract

Successful eradication schemes for bovine tuberculosis (bTB) have been implemented in a number of European and other countries over the last 50 years. However, the islands of Britain and Ireland remain a significant aberration to this trend, with the recent exception of Scotland. Why have eradication schemes failed within these countries, while apparently similar programs have been successful elsewhere? While significant socio-economic and political factors have been discussed elsewhere as key determinants of disease eradication, here we review some of the potential ecological and epidemiological constraints that are present in these islands relative to other parts of Europe. We argue that the convergence of these potential factors may interact additively to diminish the potential of the present control programs to achieve eradication. Issues identified include heterogeneity of diagnostic testing approaches, the presence of an abundant wildlife reservoir of infection and the challenge of sustainably managing this risk effectively; the nature, size, density and network structure of cattle farming; potential effects of Mycobacterium bovis strain heterogeneity on disease transmission dynamics; possible impacts of concurrent endemic infections on the disclosure of truly infected animals; climatological differences and change coupled with environmental contamination. We further argue that control and eradication of this complex disease may benefit from an ecosystem level approach to management. We hope that this perspective can stimulate a new conversation about the many factors potentially impacting bTB eradication schemes in Britain and Ireland and possibly stimulate new research in the areas identified.

Liver fluke (Fasciola hepatica) co‐infection with bovine tuberculosis in cattle: A prospective herd‐level assessment of herd bTB risk in dairy enterprises

“…This may impact the nexus between fascioliasis and bovine tuberculosis infection (Kelly et al, ; Munyeme et al, ). Wild populations may also be governed by differing ecological rules than that of managed populations (Ezenwa & Jolles, ; Graham, ), as managed populations have a very strong evolutionary pressure on the pathogen due to test and cull (as is the case of bTB in Northern Ireland), and so too on detected infected hosts (Allen et al, ). For example, Ezenwa and Jolles () found that anthelminthic treatment of free‐ranging buffalo in South Africa resulted in increased animal survival, which then led to increases in bTB risk for the population.…”

“…These findings have impact for both policy makers and practitioners invested in the management bovine tuberculosis in endemic regions, which rely upon the accurate diagnosis of infected individuals (Allen et al, ; De la Rua‐Domenech et al, ; Schiller et al, ). Co‐infection management has been proposed as an important policy approach when moving towards eradication of notifiable pathogens (e.g.…”

“…The bTB eradication programme costs over £37 million in 2017 (DAERA, ), and Northern Irish farmers bear a burden of £50 million related to production losses caused by fluke infection, and via costs of fluke control (Cooper, McMahon, Fairweather, & Elliott, ). Any association between bTB and F. hepatica infestation is therefore important in understanding the epidemiology of both diseases and guiding eradication efforts (Allen, Skuce, & Byrne, ).…”

Mycobacterium bovis uses the ESX-1 Type VII secretion system to escape predation by the soil-dwelling amoeba Dictyostelium discoideum

“…Mycobacterium bovis, a member of the M. tuberculosis complex, causes bovine tuberculosis, one of the most important veterinary health problems in the UK and Ireland [1,2]. It is also a neglected zoonotic infection in humans, causing an estimated 147,000 new infections and 12,500 deaths worldwide in 2016 [3,4].…”

Interspecific visitation of cattle and badgers to fomites: A transmission risk for bovine tuberculosis?

“…Consequently, bTB has been the focus of ongoing national, and various regional, eradication programs in both the UK and Ireland for over 50 years. Despite these programs, bTB remains a significant burden due to its complex epidemiology (Allen, Skuce, & Byrne, ).…”