Soremouth Highly Contagious in Sheep and Goats…People, Too

By Jane Fyksen Crops Editor
Thursday, November 27, 2008 8:43 PM CST

Soremouth is the most common skin disease sheep and goats get. According to a recent USDA National Animal Health Monitoring System Survey (NAHMS), 40 percent of the U.S. sheep operations report having soremouth in their flocks in the previous three years. Shepherds and goat raisers can, unfortunately, get soremouth from their livestock.

Highly contagious, it’s caused by a virus in the “pox” family. Soremouth goes by many names, including contagious ecthyma, contagious pustular dermatitis, orf and “scabby mouth.” It tends to be more severe in goats than sheep, and anecdotal evidence suggests Boer goats may be more susceptible than others, says University of Maryland Sheep and Goat Specialist Susan Schoenian.

As noted, soremouth is a “zoonotic” disease, meaning livestock can transmit it to people. Since many physicians may be unfamiliar with the disease, producers who think they’ve acquired it from infected or recently vaccinated sheep or goats should be sure to inform the doctor of their exposure to livestock.

Schoenian says in flocks that have never had soremouth, nearly all animals exposed with get the disease. The virus is transmitted by direct contact, penetrating small abrasions in the skin. Carriers (chronically infected) can serve as reservoirs of infection. Soremouth can also spread via infected equipment, even feed and bedding. Outbreaks can occur in orphaned lambs and kids sharing the same nipples. Showing sheep and goats ups the risk considerably, since livestock from different farms are in contact at exhibitions and notes Schoenian, judges may spread the virus when they examine teeth and mouths of animals in a class. Vaccinating a virus-free herd will also introduce the disease to the livestock and premises.

She says young animals are most susceptible to soremouth because they haven’t been exposed before and their immune systems are still developing. Animals that have recovered from natural infection have some resistance to re-infection. However, she says there are different strains of soremouth, and it’s possible for previously-infected animals to become infected with soremouth more than once in their lifetimes. Infections usually occur several years apart, and repeat infections tend to be less severe.

About two to three days after exposure to the virus, pustules and ultimately scabs appear. Soremouth lesions occur primarily on lips and nostrils, but may also develop on other parts of the body, like ears, eyes, feet, limbs, udder, and genital areas. Soremouth affects mostly non-wooled areas. During the course of the disease (1 to 4 weeks) scabs will drop off and areas heal.

Nursing lambs and kids can spread the disease to their dams’ teats. Schoenian says teat lesions that develop secondary bacteria can lead to serious mastitis.

She mentions there are several other diseases (some serious and “reportable” but all uncommon) whose symptoms may resemble soremouth - foot-and-mouth disease (FMD), sheep and goat pox and bluetongue.

Because it is a virus, soremouth doesn’t respond to antibiotics, nor are lesions treated unless secondary bacterial infection or a maggot infestation occurs. There’s basically not much to do for soremouth. In fact, it’s recommended crusts not be removed, as this may delay healing - and increase the handler's chance of acquiring the disease. However, ewes and does with infected udders get special care. An udder salve will help keep the scabs on the teats pliable. In worst cases, lambs and kids should be removed for artificial feeding. They should not be cross-fostered onto other females as they may infect the udders of clean females. Intramammary antibiotics can be used to prevent mastitis.

Soremouth is best prevented by maintaining a closed flock or goat herd. New animals should be quarantined until soremouth can be ruled out. Unfortunately, some can serve as carriers and slip into a flock without detection. After a herd is infected, it is difficult to eliminate the disease because the virus can remain stable in the crusts. Scabs that fall from the animals have long been incriminated as the source infection to other animals’ months or even years later.

Schoenian says the soremouth virus can survive for months, possibly years, away from the sheep. Scabs on pasture are not likely to survive the winter, but the virus may survive in barn pens and on troughs, feeders and gates.

A vaccine may be used in outbreaks. Affected animals can be isolated, while unaffected animals can be vaccinated to reduce the severity of new cases and shorten the course of infection. If the disease is already well-established, this strategy may not be successful, notes Schoenian. According to the NAHMS survey, 5 percent of U.S. sheep producers vaccinate replacement ewes for soremouth and 14 percent vaccinate nursing lambs.

The vaccine doesn’t produce a strong or long-lasting immunity. Vaccination may not always prevent animals from becoming infected, but it may reduce the severity or duration of the disease.

Since live virus is infectious to humans, protective gloves should be worn when handling the vaccine or recently-vaccinated animals. The vaccine shouldn’t be used on farms where soremouth has never been known to occur, as it will introduce the disease to the premises and necessitate annual re-vaccination. Recently-vaccinated animals should not be co-mingled with other sheep and goats, as this will spread the virus.

Pregnant females can be vaccinated two months prior to lambing or kidding to prevent natural soremouth from occurring during the nursing period. Vaccinated ewes and does should be moved to a fresh area for lambing and kidding, this Maryland sheep and goat expert suggests.

She says colostral immunity in vaccinated animals is disputed. If the vaccine does impart immunity, it’s most likely very short-lived. Work with sheep has suggested that vaccinating at the time of drying off may be preferable to vaccinating late in pregnancy. Newborn lambs and kids can be vaccinated if the risk of disease is high.

On farms that buy or show animals regularly, vaccination helps to prevent occurrence of a soremouth outbreak during the show season. Animals should be vaccinated at least six weeks (preferably two months) before the start of the show season, so vaccine scars will be gone before the first show. Flocks with soremouth are excluded from exhibition until lesions have cleared up. Health papers won’t be issued to farms with active soremouth infection.

Vaccination is usually done on the inside of the thigh of young animals and behind the elbow in adult animals. In goats, the underside of the tail is frequently used. The area is scratched to make a raw (not bleeding) area. The vaccine is applied to the raw area. A raised reddened area should result in a few days. It should be noted that this vaccine has a short life of only 10 days.

Again, Schoenian stresses that people can become infected with the soremouth virus when they come into contact with infected or recently-vaccinated animals, even when handling the live vaccine. Wear gloves and wash your hands and clothes afterwards. Soremouth can cause painful lesions, usually on the hands. Fortunately, people can’t spread soremouth to other people. Soremouth skin lesions can resemble more serious skin infections.

The Centers for Disease Control address soremouth in livestock and people at http://www.cdc.gov/ncidod/dvrd/orf_virus/#otherdiseases.

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