WHAT IS SCABBY MOUTH?
Scabby mouth (orf, contagious pustular dermatitis) is a highly contagious viral disease of the skin of sheep and goats, generally affecting lambs and kids in their first year of life.
The disease causes scabs and pustules usually around non-woolled areas such as the mouth, udder, legs, and feet.
Scabby mouth is usually a self- limiting disease that can impact productivity. It is also a zoonotic disease, meaning it has the potential to infect humans.
HOW IS IT SPREAD?
The pox virus responsible for scabby mouth survives for years in the environment, only causing signs of disease when it enters the skin through cuts or abrasions.
Once the virus is introduced to a property, it will usually remain infected but you may only see disease outbreaks every few years or so depending on the environment and management. Outbreaks most often occur when animals graze or are fed abrasive feed in paddocks, or consume hay, or stubble containing thistles or burrs. Grazing stubble also increases the susceptibility of infection due to the greater incidence of injuries to the mouth and feet. Infection of the feet often occurs when sheep are running in wet, lush pasture with thistles.
WHAT ARE THE SIGNS?
The mouth, muzzle and feet are the most commonly affected areas; however, legs, teats, the udder and the poll of the sheep can also be infected. Infection usually results in scabs and pustules around the lips. Sheep and goats infected with scabby mouth will first develop small areas of red and inflamed skin that develop into blisters then pustules. These viral filled pustules then rupture to form scabs, which is where the disease gets its name. The scabs lift in one to two weeks, exposing the raw skin which generally heals within four to six weeks after the initial infection. Rams can occasionally become infected on the scrotum causing thickening of the scrotal skin and potentially some reduction in sperm quality in hot weather.
Lesions on the teats and around the udder can predispose ewes to mastitis as well as making the ewe reluctant to allow suckling. Lesions occurring around the feet and pasterns cause lameness, leaving the animal susceptible to secondary infections such as dermatophilus (lumpy wool) and resulting in an acute lameness called "strawberry footrot".
Sheep and goats that recover from infection develop lifelong immunity against the disease. Recovered stock may be reinfected, although it is usually only a mild infection that often goes unnoticed.
IMPACT ON FLOCK
Although the disease affects sheep and goats of all ages, lambs and kids are at greatest risk of infection, with morbidity rates being as high as 100% in some flocks. Other impacts on productivity include:
- Setback in weight gains as a result of being unable to feed.
- Increased susceptibility to secondary bacterial infections in severe cases.
- Mastitis in ewes due to lesions on the teats and udder.
- Reduced semen quality in rams due to the thickening of the scrotal skin from lesions.
- Lameness from infection around the coronet and pasterns.
ZOONOSIS
People can become infected with the virus, usually on the hands, with the virus entering through a scratch or broken skin. It is important to use good hygiene when handling sheep or sheep equipment, especially if active scabby mouth lesions are present.
MANAGMENT
Treatment
There are no specific treatments. The virus normally runs its course and clears without treatment in three to four weeks. In severe cases of scabby mouth, treatment may be required to combat secondary infections.
Control
Effective grazing management strategies include:
- Move infected stock onto pastures that present a low risk of skin abrasion or injury.
- Keep pastures clean and free of thistles and burrs.
- If possible, avoid feeding hay containing thistle or burr and grazing stubble.
Vaccination
Scabigard® vaccine generates immunity by giving animals a form of the disease. The vaccine virus is capable of causing disease. It is recommended that lambs be vaccinated at the time of lamb marking and pregnant ewes not vaccinated within six weeks of lambing.
Vaccination should only be considered on properties where scabby mouth is an issue. If sheep from an uninfected property are vaccinated, this will introduce the virus on to the property. Scabby mouth vaccination is a prerequisite for some live export markets.
TAKE HOME MESSAGES:
- Scabby mouth is a highly contagious viral disease, mostly impacting lambs and kids in their first year of life.
- Vaccinating for scabby mouth can introduce the disease to a naïve property.
- Scabby mouth can be passed on to humans so good hygiene is essential.
General principles to consider when vaccinating include:
- Sterilising vaccination equipment before reuse. A specific applicator (Zoetis' Scabigard® Applicator) is required to administer the Scabigard® vaccine.
- This vaccine is different to other vaccines, as it has to be scratched into the skin. Most products require subcutaneous or intramuscular injection with a needle.
- Sheep need to be scratched on the bare skin inside the foreleg or side of the brisket to ensure a successful vaccine take. The scratch should be administered at a 45 degree angle to the skin, 4-5 cm in length and cause ample skin damage without drawing blood.
- A successful vaccine 'take' is determined when animals display a line of pustules along the scratch line, one week following vaccination.
- Sheep that are already immune to the disease may fail to 'take' the vaccine.
- Antiseptics used in lamb marking should not be allowed to contaminate the vaccination site as this will destroy the vaccine.
- Immunity from the vaccine generally develops in two weeks.
- Care should be taken when vaccinating as Scabigard® is a live vaccine and scabby mouth is transmissible to humans. Seek medical attention if you scratch yourself with the vaccine.
- Contact your local vet for assistance on implementing an effective vaccination and control program.
For further information, please contact Stock Sense on 1300 020 163 or email [email protected]
FURTHER LINKS
Agriculture Victoria - Scabby mouth (Orf)
Zoetis Animal Health - Scabby Mouth
Author; VFF, original version published November 2012, updated December 2018. Disclaimer: The Victorian Farmers Federation (VFF), its partners, agents and contractors do not guarantee that this publication is without flaw and do not accept any liability whatsoever for any errors, defects or omissions in the information provided. This publication is intended for general information purposes only and does not constitute financial, legal, investment, production or marketing advice. The VFF excludes all liability for any loss or damage of any kind arising in relation to this publication including any reliance on the information contained herein.