Contagious Ecthyma (Orf)
Global Virus Affects Sheep and Goats
Contagious ecthyma, also known as “orf” or “soremouth,” is a common malady in sheep and goats. It is caused by a parapoxvirus and is found worldwide. Though sheep and goats are most commonly affected, other ruminants, such as the musk ox or gazelle, are occasionally infected. The virus enters the body via cuts on the muzzle or mouth, usually caused by grazing on thorny brush or pasture.
Transmission and Clinical Signs
Orf first appears as blisters on the lips, muzzle and in the mouth. These blisters soon develop into crusty scabs. Lesions can also spread to the lower legs and teats, especially in ewes or does that are nursing infected young. The scabs, which contain the virus, fall off infected animals and become a source of infection for susceptible animals. In addition to the scabs, the virus can be spread via the infected animal’s saliva. Some animals may be infected, but not show clinical signs; thus, they can serve as asymptomatic carriers. Once in the soil or environment, the virus can survive for long periods of time. Infection easily passes from animal to animal or through contaminated bedding, feed buckets, water troughs, etc. Young animals are more susceptible to the virus because their immune system is not fully developed nor have they ever been exposed to the virus previously. Particular breeds, specifically Boer goats, may be especially susceptible to the poxvirus and develop more severe infections.
Infection typically lasts for three to four weeks, and, except in very rare cases, affected animals completely recover. Most animals develop only mild signs, though some, particularly younger animals, may stop eating and drinking due to pain. These animals may have difficulty nursing and will need to be supplemented with bottle or tube feeding. Nursing ewes or does may reject their young as well due to the pain associated with suckling. Older animals that develop severe clinical signs will also need additional nutritional support. Repeat infections do occur, though they usually develop more than a year after the previous infection and have less severe clinical signs.
Clinical Signs Mimic Other Serious Diseases
The signs of orf mimic Foot and Mouth Disease, which is a serious, reportable disease that affects sheep, goats, cattle, swine and other “cloven-footed” animals. If you observe signs that appear more severe than those of orf, it is important that you immediately contact your veterinarian so that you know what your animal is infected with. (The lesions also mimic Bluetongue, which isn’t reportable but poses a completely different threat.)
Vaccination Lessens Severity of Disease
Though there is a commercially available vaccine for orf, a farmer should not use it without consulting with a veterinarian. The vaccine is made from live orf virus. Therefore, the vaccinated animals actually develop a mild orf infection and shed some of the virus. The vaccine does not prevent infection, but it does lessen the severity of the disease if animals are subsequently exposed to the virus. Since vaccinated animals can shed the virus and contaminate the farm, the farmer should consider the herd’s risk of being naturally exposed to the orf virus versus the risks associated with using the vaccine. You should always consult your veterinarian to discuss your herd’s risk of infection before vaccinating. Other methods of prevention include:
- improving pastures to reduce the risk of cuts to the mouth/muzzle
- quarantining new animals for a minimum of 30 days to avoid spreading an incubating infection
- isolating known infected animals
- wearing rubber or latex gloves when handling herd members and changing those gloves when moving from one animal to another
- disinfecting all buckets, troughs and other equipment
Impact on Humans
Orf is a zoonotic disease, meaning that it is transmissible from animals to people. People become infected through contact with an infected animal, contaminated equipment or inadvertent vaccine exposure into broken skin and develop painful sores, typically on the hands. The sores can last for up to two months and usually heal without scarring. If you have contact with an animal infected with orf and have suspicious lesions on your body, you should contact your physician immediately. Because some animals may be asymptomatic carriers of orf, you should always wear gloves when handling sheep or goats, especially if working with their mouths or muzzles and if you have open wounds on your hands. Practice good hygiene by washing with soap and warm water after handling. (‘Human-to-human transmission can occur’, Smith: Large Animal Internal Medicine, fifth edition, pg 749.)
Preventative Steps Keep Animals Healthy
Contagious ecthyma is a common illness in sheep and goats and, once established in your herd, is difficult to eradicate. Knowing the signs of the virus and taking steps to prevent it will go a long way in keeping your sheep and goats healthy and disease-free.
Dr. Mary Newell Sanders practices at Marek Veterinary Clinics in Bellville and Sealy, Texas.