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Orf Virus

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What is "sore mouth" (contagious ecthyma, orf)?

"Sore mouth," also known as "scabby mouth," or contagious ecthyma, is a viral infection caused by a member of the poxvirus group and is an infection primarily of sheep and goats.

Geographically, "sore mouth" infection is commonly found throughout the world. According to the United States Department of Agriculture Animal and Plant Health Inspection Service's National Animal Health Monitoring System (USDA APHIS NAHMS) 2001 sheep survey, 40 percent of U.S. operations reported sore mouth infecting their flocks in the previous three years.

Symptoms

What are the clinical signs for sore mouth?
  • Early in the infection sores appear as blisters and then become crusty scabs. 
  • Sores are typically found on the lips, muzzle, and in the mouth (see photos below).
  • Sheep and goats may get similar sores/scabs on the lower legs and the teats, especially when ewes or does are nursing infected lambs or kids.
  • Except in rare cases, animals recover completely from sore mouth infections within a month.
  • Young animals may have difficulty nursing/feeding and may require bottle or tube feeding. Nursing ewes may abandon their lambs, and older animals may also require nutritional support. 
  • Particular breeds (e.g. Boer goats) may be especially susceptible and have severe infections. 
What causes sore mouth?

Sore mouth in sheep.
Photo courtesy Edie Lederman, MD.

Sore mouth is caused by a poxvirus (specifically orf virus) and is found all over the world. The scabs of infected animals contain virus, can fall off, remain in the environment and serve as a source of infection to susceptible animals.  A flock can become infected through contaminated bedding, feed or trucks, or by direct contact with infected animals (e.g. replacements brought onto the operation or at shows). 

Animals may become infected with sore mouth more than once in their lifetime although infections are likely to occur years apart. Young animals will have the most visible disease because they have not likely been exposed to the virus before and because their immune systems are still developing.

Which animals can get sore mouth?

Sore mouth is generally found only in sheep and goats. Other ruminants that are occasionally infected include musk oxen and gazelles.  

Are there other diseases of concern in sheep that could look like sore mouth?

Yes. Foot-and-mouth disease (FMD) is a serious disease that does resemble sore mouth and can affect sheep, goats, cattle, swine, and other "cloven-hoofed" animals.  Although FMD has not occurred in the United States since 1929, if there are symptoms you observe in your animals that appear more serious than sore mouth, immediately report it to your veterinarian, to State or Federal animal disease control officials, or to your county agricultural agent.

What can I do to protect my animals from sore mouth?

There are measures that may help lessen the risk of infection. These include:

  • Reduce the likelihood of mouth/muzzle cuts (e.g. remove thistle or harsh brush from grazing areas)
  • Quarantine new animals until sore mouth can be ruled out
  • Avoid bringing animals with sore mouth to public events such as fairs and shows

The sore mouth virus survives in soil, and carrier animals may not show symptoms; as a result it is difficult to prevent infection, but using the measures above may assist in prevention.

Sore mouth may be transmitted through saliva. Some owners choose to assist the judges at shows by opening their own animal's mouth. While there is no evidence to prove that this will prevent sore mouth, it is a logical measure to decrease the spread of sore mouth by indirect contact (i.e. from infected animal to judge's hand to uninfected animal).

 

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