Barry Whitworth, DVM
Area Food/Animal Quality and
Health Specialist for Eastern Oklahoma
Contagious Ecthyma (CE) is a highly contagious viral disease found throughout the world wherever sheep are kept. The virus primarily affects young lambs and kids within a few weeks after birth. It is also seen among weaned lambs and kids that are comingled such as in feedlot situations. Older adults not previously exposed or with compromised immune system may be affected as well as some other domestic and wild animals. Although no studies have been done, the disease most likely causes significant economic losses. Economic losses are attributed to weight loss and death loss. The disease is zoonotic, which means the virus can infect humans. The human disease is referred to as ORF. Some other common names for the disease are sore mouth, ORF, scabby mouth and contagious pustular dermatitis.
In addition to sheep and goats, the disease has been found in Alaskan mountain goats, Dall’s sheep, muskoxen, caribou, Sitka black-tailed deer, alpacas, deer, pronghorn and elk. The disease was reported to be in some dogs that were fed sheep, but the virus was not confirmed. The virus was found in three cats with skin lesions. Some believe these cats may have been immunocompromised. Rabbits, mice and Macaque monkeys have been infected experimentally.
The cause of CE is an ORF virus, which is in the genus Parapoxvirus. In small ruminants, the virus is located in skin lesions and scabs. The virus may be transmitted by direct contact with the lesions or by fomites. The virus can be found in the healed skin lesions for a short period of time. In laboratory conditions, the virus is viable in the scabs for several years. The virus is thought to enter the animal through cuts or abrasions in the mouth. Also, erupting teeth may be an entry point for the virus.
Once an animal has been exposed to the virus, clinical signs appear in a few days. The clinical signs of the disease vary in severity. Initial clinical signs are a wet mouth with red areas around the commissure of the mouth. This is followed by raised circular areas that may become vesicles and pustules. The pustules will rupture and ooze fluid on to the wool or hair. The lesions mature into scabs. The lesions are usually found on the lips, mouth and nose. Other areas where lesions may be found are the ears, eyelids, feet, genitalia and mammary glands. The lesions are painful, which leads some young animals to refuse to nurse or eat. If the feet are affected, animals may become lame. Lambs may transmit the virus to the dams while nursing. This may lead to mastitis. Ulcers may be found in the mouth on occasions. Rarely, the lesions progress into the esophagus, digestive tract, and lungs. This may result in digestive problems and pneumonia.
There have been reports with this disease of severe non-healing proliferative lesions in sheep and goats (Smith et al.) (Concha-Bermejillo et al.). The lesions are similar to the ones described above but much worse and do not heal. In these cases, additional lesions seen are swollen lymph nodes, arthritis and chronic fibrinous pneumonia. The animals did not respond to treatment for secondary bacterial infections. Antiviral treatment has not been reported in these cases.
Most veterinarians diagnose CE on clinical signs. The virus can be identified by Electron microscopy (EM). However, EM cannot separate one parapoxvirus from another. In order to confirm the ORF virus, other laboratory tests are required.
Read more in the October issue of Oklahoma Farm & Ranch.