This section contains information about TB in wildlife species, including a factsheet on badger vaccination, and information about what to do if TB is suspected in a wild deer carcase.
Many species of non-bovine farmed (e.g. South American camelids (SAC), captive deer, goats, pigs and sheep) companion (e.g. cats, dogs and ferrets) zoo and wild mammals are susceptible to M. bovis infection. Only a relatively small number of animals are identified as infected each year through scanning surveillance.
Evidence suggests that non-bovine species other than the badger are generally ‘spillover’ hosts and appear to pose a very small risk of spreading M. bovis to cattle and badgers. Wild mammals other than badgers can act as maintenance hosts for M. bovis and vectors of the infection for cattle, as illustrated by the experiences of New Zealand (brush-tailed possum), Australia (Asiatic water buffalo), Michigan (white-tailed deer), South Africa (Cape buffalo), the Central and Southern Iberian Peninsula (wild boar and red deer), and some départements of France (wild boar and red deer in addition to badgers). However, the existing evidence from wildlife surveys and quantitative risk models carried out by APHA (formerly Fera) in Great Britain indicates that in this country, the badger remains the principal and possibly the only wildlife maintenance host of M. bovis.
Whilst M. bovis infection has been found in other wild mammals in England (notably deer and more rarely wild boar, fox and some rodents), the data on the prevalence of infection, pathology, abundance and ecology suggest that fallow deer and possibly muntjac and red deer are the only other wild mammals that could act as potential sources of M. bovis for cattle in England and Wales. Even in these deer species, the effect is localised and the risk of transmission to cattle much lower than that posed by badgers, primarily due to differences in behaviour and contact levels with cattle. Additionally, once detected, deer infection is often controlled locally by additional culling.
Wild deer surveillance is carried out by private stalkers who are aware of the need to submit suspicious lesions for bacteriological examination. Where there is a suspicion of deer-related tuberculosis infection in cattle, this surveillance can be intensified and additional surveillance of cattle in an area can be initiated by APHA when considered appropriate. APHA continues to monitor the results of scanning surveillance in wild mammals.
Feral wild boar
There is sparse information available about feral populations of wild boar in England. They are currently thought to be present in a limited number of localised populations at low population densities. They are normally only infected with TB in areas where infection is widely found in cattle and badgers.
A small number of isolations of M. bovis are made from feral wild boar each year, and the genotypes are usually identical to those isolated from the local cattle.
In England, feral wild boar are thought to act as spill-over, sentinel hosts of M. bovis, and current evidence suggests that the risk of transmission of M. bovis between cattle and feral wild boar is very low. In other countries such as France and Spain, there is however evidence that they can act as reservoirs of infection and transmit tuberculosis to cattle. Widespread tuberculous lesions have been found in feral wild boar in Spain suggesting that these animals can shed the bacterium and contaminate the environment.
Therefore, feral wild boar in England should be regarded as potential amplifier hosts for M. bovis. If evidence emerges that feral wild boar are playing a significant role in the epidemiology of TB in England, measures could be taken to control the population.
Useful resources
- Factsheet on TB in deer and other animals
- APHA information sheet on reporting suspicion of TB in a wild deer carcase
- Research Gate. Delahay RJ, Smith GC, Barlow AM, Walker N, Harris A, Clifton-Hadley RS(2007). Bovine tuberculosis infection in wild mammals in the South-West region of England: A survey of prevalence and a semi-quantitative assessment of the relative risks to cattle.