Crossroads Veterinary Services (706) 743-7614 or (706) 224-3200

Cervids include deer and their allies, including moose, elk and caribou. Cervids are ruminants and have a similar physiology as our bovine patients with regards to nutrition. Cervids can be afflicted by a variety of bacterial, viral and parasitic diseases affecting domestic ruminants. The following diseases can occur in cervids:

1. Bacterial

1. Brucella abortus: As in other ruminants, brucellosis infection can result in abortion, arthritis and debilitating disease. Bison, elk and cattle can be persistent carriers and the disease can become an endemic problem with appropriate population size, density and management. Other cervids rarely develop clinical disease or endemic infections.
2. Johne's disease: the disease is common in ruminants worldwide and is transmitted by close contact/ingestion or transplacentally from dam to fetus. The incubation period is long, often several years, prior to the appearance of clinical signs of disease. It causes granulomatous enteritis and lymphadenitis, with chronic weight loss despite a good appetite, diarrhea and eventually death. Definitive diagnosis is difficult due to the prolonged culture times required and the likelihood of false negatives on fecal culture. Purchasing cervids from a farm without history of Johne's disease is recommended.
3. Tuberculosis is a density-dependent disease in ruminants and is transmitted via the gastrointestinal tract or respiratory tract.
4. Yersiniosis is primarily a disease of red deer and is an organism present in soil, water and feces. Certain strains with virulence factors affect the intestinal tract, resulting in diarrhea, weight loss and systemic infection. Losses can be significant and the disease is difficult to treat.
5. Anaplasmosis is caused by the vector borne rickettsial organism Anaplasma marginale. It causes subclinical infection in an array of wild ungulates in the United States, and is capable of causing hemolytic disease in cattle (Radostits et al., 1994). Certain species of ticks act as biological vectors while tabanid (horse) flies act as mechanical vectors.

2. Viral

1. Adenoviruses commonly affect ruminants and result in subclinical disease and occasionally result in gastrointestinal, respiratory or hemorrhagic syndrome. The epidemiology of these viruses are incompletely understood in cervids.
2. Bluetongue is an orbivirus transmitted by Culicoides midges and endemic in the southern USA. Cattle are the major reservoir with goats and elk as sublinical carriers
3. Chronic Wasting Disease (CWD) is a prion-associated transmissible spongiform encephalopathy (TSE). Animals develop behavioural changes, increased drinking/urination, excess salivation and difficulty swallowing, occasionally some ataxia, and in all cases, loss of body condition progressing to emaciation. The pattern is sporadic, and the minimum incubation period seems to be about 18 months in mule deer and elk. Transmission is horizontal, by contact, and possibly vertical/maternal, from dam to offspring, even with minimum contact after birth. The disease has been recognized in wild elk, mule deer and white-tailed deer in Colorado and Wyoming. The origin of CWD is unknown. There is no clear epidemiologic association with spongiform encephalopathies of domestic animals. Since the affected captive herds were established with wild animals prior to recognition of the disease in free-ranging animals, it is possible that CWD was introduced from the wild population, where it was unknown at the time.
4. Epizootic Hemorrhagic Disease (EHD) is caused by an orbivirus closely related to Bluetongue virus. The two viruses often cocirculate and the diseases are indistinguishable without virus isolation. It is transmitted by Culicoides midges. The virus does not appear to over-winter in arthropods, and the disease dies out as the vector arthropods die in fall/winter. A variety of domestic and wild ruminants likely form the reservoir in the southern United States. The disease is rarely recognized in domestic animals. Among wildlife, white-tailed deer are especially susceptible to EHD, while other species, including elk, may develop mild or subclinical disease.
5. Herpesvirus infections are ubiquitous among ruminants. In cervids, infections occur with herpesviruses apparently native to deer and with the sheep or wildebeeste origin herpesviruses, which cause malignant catarrhal fever. Alpha herpesviruses of ruminants typically cause mucosal infections and may produce latency in neurons. Two herpesviruses, CHC-1 and CHV-2, have been isolated from red deer; the former was associated with conjunctivitis in farmed red deer calves in Scotland. Rangiferine Herpesvirus-1 was isolated from a reindeer. CHV-1 and RHV-1 are related to Bovine herpesvirus-1, the cause of infectious bovine rhinotracheitis. A herpesvirus related antigenically to Equine Herpesvirus-1 was isolated from fallow deer in Alberta. Only CHV-1 has been associated with disease in farmed deer, and no herpesviruses have been firmly associated with disease in wild deer. However, antibodies that react with BHV-1 have been detected in Quebec caribou, and in black-tailed deer and white-tailed deer in the USA.
6. Malignant Catarrhal Fever (MCF) is caused by a cell-associated (herpesvirus, either Alcelaphine Herpesvirus-1 transmitted from wildebeest (an issue in zoos), or Ovine Herpesvirus-2 (OHV-2) transmitted from domestic sheep. Until recently, tests were not available to detect carrier sheep or wildebeest, and they are still not routine. The hosts of origin (wildebeest, sheep) do not develop disease, but the carrier state is widespread and common among them. Disease occurs in cattle, bison, and most species of cervids. Transmission is by exposure of the susceptible species to the carrier host, usually by close contact, since the virus is not persistent in the environment. There is little, if any, horizontal transmission of disease among individuals of the susceptible species, despite the fact that they show severe signs (ocular, nervous, orocutaneous, respiratory and gastrointestinal mucosal ulceration). They are considered "dead end" hosts from the standpoint of disease transmission. Virtually all deer which develop clinical MCF go on to die.
7. Parapoxviruses usually cause mild transient infections in their native host, but can cause severe disease in unnatural hosts; however, the capacity to cross-infect, and the reaction in the unnatural host, are unpredictable. No parapox infections have been recognized in native deer in North America and the only cervid in which a parapox infection is described is the red deer. In red deer, lesions of the skin and velvet antler were associated with cutaneous trauma due to thistles in paddocks. The overall impact of the disease is mild.

3. Parasitic

1. The principal ectoparasites (external parasites) of concern on deer are mites, especially Psoroptes. sp. and ticks, especially the winter tick Dermacentor albipictus and the black-legged tick Ixodes scapularis.  Psoroptes causes scabies on deer, including elk and white-tailed deer, in which it may also cause otitis and it also infects mule deer. Psoroptic scabies does not seem to be a clinical problem in red deer and fallow deer, but Sarcoptes mites have been recorded from red deer in Europe.  Dermacentor albipictus causes severe alopecia in moose, and does infect elk and white-tailed deer. Ixodes scapularis is the vector of Lyme borreliosis. It is endemic in parts of the northeastern and upper midwest USA.
2. The nematode Elaeophora schneideri, which inhabits arteries in the head and neck, infects mule deer with little effect, but causes problems with mastication in white-tailed deer; blindness, brain damage and gangrene of the tissues of the head in moose and elk; and less severe effects in sika deer and sheep and goats. The normal host in the western United States is the mule deer and white-tailed deer are usually not infected. In the southeastern USA, white-tailed deer are the normal host. Elaeophora uses certain species of tabanids (horse flies) as vectors.
3. This protostrongylid nematode, though it lives at sites distant from the lungs, produces eggs which reach the lungs via the circulatory system. The eggs hatch in the lungs and the first-stage larvae move up the trachea, and are swallowed, to be passed in feces. They use molluscs (snails or slugs) as intermediate hosts. Infectious larvae in molluscs accidentally ingested by deer, migrate from the gut to the spinal cord and brain, then, in most cases, to intermuscular tissues, where they mature. During their migration in the central nervous system, these worms can cause damage which may result in clinical disease.
4. Gastrointestinal nematodes, predominantly Trichostrongyloidea, are common in all ruminants, including deer. Infections typically involve a complex of species of worms, but are usually dominated by one. Those found in deer are usually species related, but not identical, to those in domestic ruminants, and even when they are the same species, they seem to be host-adapted. Parasites exotic to the new world certainly have been imported with their hosts to North and South America. Parasites of deer non-indigenous to Ontario may not transmit effectively to indigenous species of deer, although cross-infection by some species clearly can occur from white-tailed deer to exotics in areas of sympatry. Worms parasitizing the abomasum (true stomach), belonging to the genus Ostertagia or its relatives, are pathogenic in fallow deer, red deer and wapiti, causing diarrhea and weight loss, as do their relatives in sheep and cattle. Related worms are found in wild white-tailed deer in Ontario. Haemonchus species cause anemia in white-tailed deer in the southeastern United States, where, under warm, humid conditions, parasite burdens can be heavy. Under conditions prevailing there, worm burdens are host-density dependent, and have been used as a management tool in measuring deer population density in relation to habitat quality.
5. Lungworms of the genus Dictyocaulus occur in all species of deer and seem to be particularly pathogenic in red deer and elk. Most lungworms of deer (red deer, elk, white-tailed and black-tailed deer, reindeer and caribou, and moose) on morphologic grounds are termed D. viviparus, which is the lungworm of cattle. Transmission is direct (no intermediate host). Cross infections do occur, but cross-infectivity of these worms among hosts in some cases seems to be incomplete. When it has been attempted (ie. infectivity is best or pathogenicity is greatest in the host of origin, compared with the alternative host). Dictyocaulus is an important pathogen of red deer, elk and fallow deer in captivity. Heavy infections can occur in wild deer, especially white-tailed deer in the southeastern United States.

Further discussion on some of the above diseases is available under the zoonotic and emerging diseases section of our website.