The status of tuberculosis in European wild mammals

Abstract

Tuberculosis (TB) is a chronic disease caused by Mycobacterium bovis and related members of the Mycobacterium tuberculosis complex. Infection affects not only cattle but also other livestock species, companion animals and wild mammals. Humans are also susceptible; hence, zoonotic infection is a driver for disease control in animal hosts. As bovine TB prevalence has been reduced in livestock, the relative epidemiological and socio‐economic importance of wildlife reservoirs has increased, and there is a need for disease management strategies. We review the current status of TB in European wild mammals, identifying epidemiological trends and areas for future research and management. TB has a complex epidemiology, which may involve multiple hosts, and is influenced by climate and habitat. Consequently, the role of wild and domestic hosts in the epidemiology of TB varies among regions. In Europe, there are three regional examples of M. bovis maintenance hosts: the Eurasian badger Meles meles in Great Britain and Ireland, the Eurasian wild boar Sus scrofa in the Iberian Peninsula and deer belonging to the subfamily Cervinae in several European regions. In other parts of Europe, these species are currently regarded as spillover hosts, although in time their status may change depending on local or regional risk factors. Nevertheless, in most situations, the relative contribution of wild mammals to M. bovis infection in cattle is still a matter of debate. Also, the outcome of management interventions to control disease in wildlife populations may be complex and counter‐intuitive. As our knowledge of disease dynamics in wild mammals improves, options for disease control in wildlife reservoirs, such as vaccination, improved biosecurity and population management, are likely to broaden. In order to evaluate our existing control options, we must monitor the effects of interventions on TB occurrence in the affected regions of Europe and share our collective experiences.

Interactions between four species in a complex wildlife: livestock disease community: implications for Mycobacterium bovis maintenance and transmission

“…Primarily caused in cattle by Mycobacterium bovis infection, this bacterial disease can spill over into human and wildlife populations. Wildlife reservoirs have been identified in brush-tailed possums (Trichosurus vulpecula) in New Zealand (Anderson et al 2013); badgers in the England, Wales and Ireland (O'Connor et al 2012); wild deer in the USA and Canada (Nishi et al 2006;O'Brien et al 2011); buffalo and other wildlife in South Africa (Renwick et al 2007) and European bison (Bison bonasus) and wild boar (Sus scrofa) in Europe (Naranjo et al 2008;Gortázar et al 2011;Krajewska et al 2015). In an infected animal, M. bovis can be excreted in all bodily fluids, meaning transmission is possible directly through close contact (aerosol transmission, meat or milk ingestion) or indirectly via contact with fluids or excreta in the environment (Neill et al 2001;Radostits et al 2007).…”

Scientific Opinion on the public health hazards to be covered by inspection of meat from farmed game

“…The goal of TB eradication in cattle requires the development of strategies that reduce pathogen transmission between wildlife and domestic animals and between non-bovine livestock and cattle (O'Reilly and Daborn, 1995). In Europe, three wildlife hosts are regionally defined as maintenance hosts, meaning they are able to maintain and transmit the infection to other species including cattle: the Eurasian badger (Meles meles; mainly in the British Islands), the Eurasian wild boar (mainly in the Iberian Peninsula) and deer of the subfamily Cervinae (red, sika and fallow deer) in several regions (Gortázar et al, 2012). The latter two hosts (or host groups) are also occasionally farmed and thus belong to the farmed game.…”

“…Consequently, we can have little confidence that TB infection is truly absent in wild mammal populations in many countries, despite the absence of reported cases. Moreover, it has been speculated that, given the current geographical and numerical expansion of wild hosts of TB in parts of Europe and the emergence of risk factors related to habitat change and game management, including farming, fencing and feeding, the importance of wildlife in the epidemiology of Mycobacterium bovis infection in domestic animals may continue to grow in the near future (Gortázar et al, 2012).…”

“…Wild deer TB has been described in 10 European countries in the last decades, including both Offically Tuberculosis Free (OTF) and non-OTF MSs: Austria, France, Germany, Hungary, Italy, Poland, Portugal, the Republic of Ireland, Spain and the UK (Gortázar et al, 2012). The best-known situation is currently that in Spain, where the mean prevalence of 10-15% of red deer with TB compatible lesions have been reported , and local culture-confirmed infection prevalence ranges up to 27 % in red deer and 18 % in fallow deer in parts of the country .…”

“…Wild boar TB has been reported in the last decades in at least 10 European countries: Bulgaria, Croatia, France, Germany, Hungary, Poland, Portugal, Slovakia, Spain and the UK (Gortázar et al, 2012). Wild boar experience much higher levels of exposure than deer .…”