Wild deer are highly susceptible to TB infection. In Great Britain they are generally considered to be spill-over hosts of TB i.e. they are unlikely to sustain the infection within their own population in the absence of infected cattle or a wildlife reservoir. The wild deer population in GB has been estimated to be well over two million with an annual cull of over 300,000.
There are usually only a few isolations of M. bovis from wild deer each year in GB. There is evidence that wild deer can be a reservoir of TB and can transmit TB both to other deer, and to cattle. This can occur where wild deer live or congregate at high population densities and commonly interact with cattle e.g. in South West England and the northern USA.
Deer are not a protected species, so if evidence emerges that wild deer are involved in the spread of TB in a particular location, measures could be taken to control the population. If TB is suspected in a wild deer carcase then it must be reported to the Animal & Plant Health Agency. In the High Risk and Edge Areas of England, confirmation of disease can be valuable information used to guide herd management and biosecurity decisions by local cattle keepers. Confirmation of TB in wild animals can lead to TB testing changes for neighbouring cattle herds in the Low Risk Area of England only.