The management of wild deer in Scotland: Deer Working Group report

Annex 7 - Notes on some Notifiable Diseases affecting wild deer

Bovine Tuberculosis (TB)

While primarily a cattle disease, TB is found in deer, is endemic and zoonotic, with affected humans developing a TB very similar to the normal type. It can be passed between most mammals. Deer are generally considered to be ‘spill-over hosts’, meaning that they are unlikely to sustain the infection within their own population in the absence of infected cattle or other wildlife. However, they do have the potential to transmit disease to other susceptible co-located species, including cattle and also to humans with close contact. The view that deer appear to pose only a small risk of spreading TB to cattle is questioned by some academic studies, with fallow showing 2.6 – 6.5% prevalence, muntjac 1.0 - 14.4% , red 0.1 – 3.5% and roe 0.4 – 1.9% . In contrast, badgers show 9.7 – 12.2% prevalence and foxes 2.0 – 4.7%. Red and fallow deer in particular may play a ‘potentially substantial’ role in maintaining infection levels in an area, particularly if densities are high.^[3] The Tuberculosis in Specified Animals (Scotland) Order 2015 revoked all previous legislation for TB in non-bovine species and introduced a regime of TB controls covering deer and other susceptible species.

Foot and Mouth

The last outbreak in the UK was in 2007. Deer are classed as ‘susceptible’ and are therefore under movement and carcase restrictions during an outbreak. Some cases of the disease in deer were reported in the press during the 2001 outbreak but this evidence is disputed. The disease can be fatal in roe and muntjac, with other species acting as reservoirs for unknown periods of time. Laboratory tests for the virus are undeveloped for the disease in deer, with cattle and sheep testing procedures being used with an unknown efficacy of detection, which may have contributed to the uncertainty about the occurrence in deer during past outbreaks.

Chronic Wasting Disease (CWD)

This is an exotic disease, which is not transmissible to humans. It is a transmissible spongiform encephalopathy (TSE), similar to scrapie. This disease has not been identified in Scotland, nor is there any evidence to date of TSE in deer in the UK. However, it has been reported in Norway in reindeer and moose (2016) and is widespread in USA. If it was to become established in the wild deer population in the UK, it would have major consequences for deer populations. A leaflet has been produced by Scottish Natural Heritage in partnership with the Scottish Government and other members of a CWD Expert Working Group, which is aimed at raising awareness of the disease.^[4]

Warble fly

Flies of the genus Hypoderma are widespread through the northern hemisphere. Two species cause disease in cattle (H.bovis and H. lineatum). The resulting disease caused by these species (‘Warbles’) is a notifiable disease in Scotland only. Deer are susceptible to both these species. Another species, H. diana, continues to affect deer throughout the UK. Warbles was widespread prior to the 1980s and was finally eradicated in 1990, having been made notifiable in 1982. The main legislation on warble fly is the Warble Fly (Scotland) Order 1982. A related species, H. tarandi, is found in the boreal zone where zoonosis has been reported. This latter species has also been found in red deer in Norway, where reindeer are the normal host. If warble fly is reported in Scotland, the actions identified in the contingency plan for exotic notifiable diseases will be followed.^[5] Another parasitic fly that is a member of the same family as warble flies, the nasal bot fly, can affect deer and while harmless, can cause them significant irritation.

Bluetongue

This is an insect-borne viral disease that affects all ruminants, including deer, but most severely sheep. It cannot be spread directly between animals and relies on the midge as a vector for transmission. The disease does not affect humans and there are no public health or food safety implications. While not present in Scotland, an outbreak occurred in Dumfries in 2017 as a result of imported cattle. The significance of deer as a reservoir species is unknown, although this is thought to be significant in continental Europe.

Epizootic haemorrhagic disease

A similar viral disease to bluetongue, principally affecting deer but not yet recorded in UK. It is associated with lower latitudes than Scotland’s and has not yet been recorded in Europe. It is present in the USA, Africa, Asia and Australasia.

Footnotes

3 Bovine Tuberculosis Workshop, ‘TB Wildlife Reservoirs’, University of Glasgow, 9-10 May 2013.

4 SNH, ‘Chronic Wasting Disease of Deer’ leaflet, 2017.

5 Scottish Government (2017). Exotic Animal Disease Contingency Framework Plan, Version 5.