This section of the website provides concise and accessible information on the different diseases which can affect wild deer in Scotland, including up to date information relating to Foot and Mouth Disease and Bluetongue.
FOOT AND MOUTH DISEASE
Following the outbreaks of Foot and Mouth in 2007, Scottish Government officials are reviewing lessons learnt. When available the results if this review and changes arising will be published in this section.
Symptoms
Foot-and-mouth disease (FMD) is an acute infectious disease, which causes fever, followed by the development of vesicles (blisters) - chiefly in the mouth and on the feet. The disease is caused by a virus of which there are seven 'types', each producing the same symptoms which are distinguishable only in the laboratory.
FMD is probably more infectious than any other disease affecting man or animals and spreads rapidly if uncontrolled. Cattle, sheep, pigs, goats and deer are susceptible. Elephants, hedgehogs, rats and any wild cloven-footed animals can also contract it. FMD is endemic in parts of Asia, Africa, the Middle East and South America, with sporadic outbreaks in disease-free areas. The interval between exposure to infection and the appearance of symptoms varies between twenty-four hours and ten days, or even longer. The average time, under natural conditions, is three to six days.
After-Effects
Foot-and-mouth disease is rarely fatal, except in the case of very young animals, which may die without showing any symptoms. In very rare exceptions, a severe form of the disease may cause sudden death in older animal stock.
The after-effects of the disease vary. In addition to treating and nursing a herd or flock of sick animals, a reduction in the milk yield in a dairy herd will certainly be experienced, at least until the next lactation. Mastitis may develop and in some cases chronic heart disease occurs. The raw surfaces left on the foot when the blisters burst are likely to become infected; this may lead to lameness and loss of a hoof.
Infection
The virus is present in great quantity in the fluid from the blisters, and it can also occur in the saliva, milk and dung. Contamination of any objects with any of these discharges is a danger to other stock. At the height of the disease, the virus is present in the blood and all parts of the body. Heat, sunlight and disinfectants will destroy the virus, whereas cold and darkness tend to keep it alive. Under favourable conditions it can survive for long periods.
Airborne spread of the virus can take place and under favourable climatic conditions the disease may be spread several miles by this route. Animals pick up the virus either by direct contact with an infected animal, by contact with foodstuffs or other things which have been contaminated by such an animal, or by eating or coming into contact with some part of an infected carcase.
Foot-and-mouth disease is extremely infectious. A very small quantity of the virus is capable of infecting an animal and it is easy to realise how rapidly the disease could spread throughout the country if no attempt were made to control it.
Trucks, lorries, market places, and loading ramps - in or over which infected animals have travelled - are dangerous until disinfected. Roads may also become contaminated, and the virus may be picked up and carried on the wheels of passing vehicles.
The boots, clothing, and hands of a stockman who has attended diseased animals can spread the disease. Dogs, cats, poultry, wild game and vermin may also carry infection.
BLUETONGUE DISEASE
The current appearance of Bluetongue Disease in Suffolk has great significance for both the farming and wildlife populations of the UK. Bluetongue is a well recognised disease of ruminant animals in many parts of the world. Although it has affected large areas of northern Europe since 2006 the UK has always remained free of the infection.
Infection and Symptoms
The disease is caused by a virus and spread by biting midges. It is not infectious from animal to animal but depends upon the insect vector to transmit the virus from one animal to another in much the same way as malaria is transmitted from person to person. A wide range of ruminants may be infected by the virus but the response varies considerably from species to species. Of the domestic animals, sheep are the most seriously affected, with severe disease in adult sheep causing high mortality. Signs include swelling of the head, high fever, nasal discharge, lameness, pneumonia and interference with the blood supply to the tongue and lips, which turn blue or even black. In milder outbreaks, clinical signs may be less severe but abortion, stillbirth and weak, fading or deformed lambs occur. Cattle are usually either only very mildly affected, or are not affected at all – although the current disease in Suffolk was first recognised in a cow; other cattle as well as sheep are now being tested. The type of virus in Suffolk has been identified as BTV8, which is the same strain as in the recent outbreaks near the English Channel and North Sea coasts in Europe. It probably arrived with a wind borne midge.
Some parts of the southern USA have continual and persistent infection, as do some parts of Mediterranean southern Europe and many other sub-tropical agricultural economies are plagued by the disease.
Bluetongue and Deer
The virus belongs to a closely related group of viruses that includes the virus causing African Horse Sickness and a severe disease of deer called Epizootic Haemorrhagic Disease [EHD]; in fact, the deer virus and the sheep virus are so closely related that some scientists believe that they are simply variations of the same virus. Others believe that the viruses are distinct, but very similar. The deer disease [EHD] causes serious and fatal signs in white tailed deer in many parts of the USA and Canada. Outbreaks sometimes kill hundreds of animals, usually mostly white tails, but in severe incidents mule deer and pronghorn antelopes are also affected and may die. The clinical signs in deer are the same as the signs in sheep with Bluetongue. Rather perversely white tailed deer are also the most seriously affected by true Bluetongue virus, leading to great confusion in southern States of the USA where both diseases are endemic. Red deer, fallow deer, muntjac and roe deer are all potential hosts of the Bluetongue virus and in experimental inoculations with EHD all four species developed a period of infection, with multiplication and shedding of the virus, but none developed serious disease.
Almost all Eurasian deer species are members of the subfamily Cervinae, which contains species like the red deer, sika, fallow, axis, the rusa and swamp deer. Wapiti, or American elk are also classified within this sub family and just like red and sika, can hybridise with European red deer. Most of the New World deer like the north American white tailed, the mule deer and the South American brocket deer, marsh deer, pampas deer and pudu are members of a different sub family of deer, the Odocoilinae. Bluetongue virus appears to be much more able to become established and to cause disease in the Odocoilinae deer [for instance the white tailed] than in the Cervinae species. The roe deer is a member of the Odocoilinae, not the Cervinae and is therefore muc more closely related to American white tails than to British red or fallow. Although there has been a little work with EHD virus in roe, not a great deal is known about the pathogenesis of true Bluetongue in roe, which is generally a deer species of northern latitudes where Bluetongue has not traditionally occurred.
At present it is unknown whether any of our native wild deer species are susceptible to BTV8 because, as far as we know, Scottish midges and Scottish deer have never been naturally exposed to the virus. It is likely that they are susceptible; however, there is no evidence from Europe yet to suggest that bluetongue is a significant disease for wild deer, or that wild deer play any role in perpetuating the disease for domesticated ruminants. Indeed, information to date indcates that the prevalance of the disease in wild deer in Europe is surprisingly low given the high prevalence of bluetongue in domestic livestock. This is in contrast to the situation in the North America, where clinical disease appears common in wild deer.
The UK bluetongue experts group, which provides scientific advice to Governement on dealing with the disease, previously considered active testing of wild deer in East Anglia for bluetongue. However, since there is no evidence to date from passive surveillance for clinical signs that bluetongue is present in wild deer within the restricted zone, or anywhere else in GB, it was agreed that sampling deer was not currently warranted; that position will be kept under review.
It would be hard to justify doing anything more in Scottish deer at this stage, and in fact the domestic cattle and sheep population should provide the best evidence of bluetongue prevalence. However, as we do not know a lot about how this strain of bluetongue will behave in Scottish deer, we would welcome increased vigilance by deer managers and we will continue to liaise with Scottish Government Animal Health officials..
