Predicting the status of wild deer as hosts of Mycobacterium bovis infection in Britain

Abstract

Control of livestock diseases can become complicated when wild animals are involved. The Eurasian badger (Meles meles) is considered the principle wildlife host of Mycobacterium bovis (which causes bovine tuberculosis, bTB) in Great Britain and Ireland, but wild deer have also been implicated. Whether wild deer are likely to perpetuate bTB in cattle depends on the exposure risks they pose, the mode of pathogen transmission, the distances over which the disease can be transported and whether they can maintain infection within their own populations independently of other sources. We evaluated the likely host status of each of four species of wild British deer (red, roe, fallow and Reeves' muntjac) and the badger across a range of densities typically observed in Britain by manipulating the reproductive number equation proposed by Anderson and May (1991). We estimate that roe deer almost certainly act as spillover hosts at densities lower than 30 km −2 , red deer below 16 km −2 , muntjac below 6 km −2 , fallow below 4 km −2 and the badger below 2 km −2 . We also estimate that muntjac will almost certainly act as maintenance hosts at densities above 56 km −2 , fallow above 47 km −2 and badgers above 24 km −2 . For densities between these values, we cannot be certain of the host status of these species, and for red and roe deer we cannot be certain of host status under most natural conditions typically experienced in parts of Britain experiencing high incidence of bTB in cattle. However, enhanced transmission rates resulting from artificially high densities such as might be experienced at supplementary feeding sites may be sufficient to promote independent maintenance of infection. We were not able to confidently assign host status to any species over a wide range of densities, but conclude that this is likely to reflect reality, where host status may be affected as much by, for example, demographic fluctuations as it is by population density. Our results imply densities below which populations of wild deer inhabiting cattle bTB hotspots ought to be maintained in order to control the possibility of them perpetuating the cycle of intra-and interspecific M. bovis transmission.

Dynamic Network of Interactions in the Wildlife-Livestock Interface in Mediterranean Spain: An Epidemiological Point of View

“…Three scenarios of theoretical probability of infection were considered: 0.1, 0.2 and 0.5. The probability of infection given interaction in wild conditions is a difficult parameter to estimate, so we selected these values according to a range of β parameter presented in previous works, which modeled the transmission of a pathogen transmitted through direct pathways (foot and mouth disease [FMD]; [58,59]) and indirect pathways (animal tuberculosis [TB]; [60]). These are two relevant infectious diseases in Spain since, although this country has been FMD free since 1986, there is a real risk of pathogen introduction through animal imports [61].…”

Modeling current and potential distributions of mammal species using presence‐only data: A case study on British deer

“…Reports published over the past decade or so suggest that most of these populations have been steadily growing (Battersby, ; Mathews et al, ; Ward, ). In large numbers, deer can inflict substantial damage to woodland and crops (Putman & Moore, ) as well as providing a reservoir for the transmission of diseases, some of which can affect livestock and human health, for example, bovine tuberculosis (Ward & Smith, ) and foot‐and‐mouth disease (Böhm, White, Chambers, Smith, & Hutchings, ). In contrast, their populations may be threatened by the introduction of novel diseases, such as chronic wasting disease (Ricci et al, ) which has severely impacted some cervid species in the USA (Monello et al, ) and has recently been reported in Europe (Benestad, Mitchell, Simmons, Ytrehus, & Vikøren, ).…”

Impact of external sources of infection on the dynamics of bovine tuberculosis in modelled badger populations

“…Where these external sources of infection include maintenance hosts, disease control strategies should include management of these other potential sources of disease. However, effective control of bTB in the badger population may also help to reduce the significance of these external sources, especially if the other species are acting solely as spillover hosts [ 32 ]. With larger group sizes, even occasional infectious disease contact can cause low levels of disease to persist, thereby complicating control measures.…”

“…However, only some of the affected species excrete bTB and are therefore capable of contributing to a pool of external infection. Of the affected species, only fallow deer and muntjac, at densities of over 56 per km 2 and 47 per km 2 respectively, are likely to act as maintenance hosts [ 32 ]. Spillover host status may be provided by roe deer, red deer, muntjac and fallow deer at lower densities [ 32 , 34 ].…”

“…Of the affected species, only fallow deer and muntjac, at densities of over 56 per km 2 and 47 per km 2 respectively, are likely to act as maintenance hosts [ 32 ]. Spillover host status may be provided by roe deer, red deer, muntjac and fallow deer at lower densities [ 32 , 34 ]. However, the capacity of these species to maintain the disease as part of a multi-species host community has yet to be explored, and it may provide further opportunities for external infection to the badger population, as well being able to act as a spillover for bTB from badgers.…”