Orf / Vuilbek

Orf, Scabby mouth or ‘Vuilbek’ in Angora goats

‘Orf’ ‘Vuilbek’or ‘scabby mouth’ is an infectious viral disease of the pox virus family.

The virus affects goats of all ages but kids are most susceptible.

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How do kids get Orf?

The virus is spread by direct and indirect contact and enters through any abrasion in the skin. Abrasions to the lips and muzzle while browsing makes this area the most common site for the lesions to occur.

  • Spread to the gums and inside the mouth and nose can then take place.
  • Bites from midges can be a site of entry for the virus, typically causing lesions on the eyelids, ears and genitals.
  • Suckling kids causing micro-trauma to the teats of ewes makes this a potential site for infection and transmission from the kids.
  • Wet conditions can cause softening of the skin around the hooves resulting in abrasions and therefore infection typically between the claws ‘strawberry footrot’.

In severe cases, the spread of the virus becomes more generalised. The generalised form is often fatal with extensive lesions of the mouth, pharynx, oesophagus and even the rumen.

  • Secondary bacterial infection of the lesions can cause mortality which can be greater than 20% depending on the secondary complications. Pneumonia is the most common cause of mortality.
  • Vitamin A deficiency, poor hygiene and stress may predispose animals to severe forms and complications.

How long can the pox virus survive on a farm?

The virus is very resistant to heat and drying out and so can survive from one kidding season to the next. Ewes can transmit the virus to the kid during parturition. Permanently infected goats can develop, resulting in an endemic situation on the farm. 

What are the time frames for the development of the Orf lesions?

  • Lesions start to appear 2-6 days after the virus is introduced. The lesions start as reddish papules which change to yellowish pustules after a few days.
  • By about 11 days they become covered with dark brown scabs.
  • The scabs come off within 2-4 weeks without leaving a scar.

How does Orf effect kids and ewes?

When the lesions become severe (cauliflower-like appearance) the goats will show signs of pain, poor appetite (or reluctance to suckle) and lose weight. Ewes with lesions on their udders or teats often will not allow the kids to suckle.

Treatment

Treatment is purely supportive but does shorten the duration of clinical signs of the virus. Remember the Pox virus is a Zoonosis (humans can get it) so wear gloves when treating the lesions

  1. Crusty or scaly material must be removed (use a disinfectant scrub like F10 or Bioscrub Chlorehexidine). Vigorous cleaning of the lesions which causes them to bleed and treats the secondary bacterial infection, but it is also thought to stimulate the immune response (possibly viral particles entering circulation) in the effected animal

 

  1. Farmers report a good response to the application of an off-label mixture to form a paste which is applied after cleaning.
  • 20% Kerol and 80% linseed oil (or cooking oil) - mix in Zinc Sulphate 5g/100ml of the mixture (or Sulpher)

This also helps keep the lesions moist and prevents them from drying and cracking causing discomfort.

 

  1. Some farmers have used ‘Greasy Heal’ a horse product after cleaning to good effect (but is expensive)

 

  1. Goats that are badly effected also consider:
  • Anti-inflammatory injections to reduce pain in animals that are reluctant to eat.
  • The use of antibiotics to prevent secondary infections can be justified. Of the injectable antibiotics, long-acting penicillins seem to be the most effective at controlling secondary bacterial infections.
  • Valuable animals with severe oral lesions can be stomach tubed to be fed.

 Blowfly strike is always a risk so must be closely monitored.

Prevention

  1. Vaccination against Orf is available, but its limitations should be understood.

 NB: DO NOT VACCINATE if you have never had the problem on your farm as you will just be introducing the virus

If an animal is vaccinated or exposed to a natural infection, further exposure to the virus is still likely to cause disease, but the scabs which form will be less severe and will drop off more quickly (10-14 days instead of two to four weeks). This means animals are contagious for a shorter period and will have a knock-on effect in reducing the overall contamination level of the environment and infection level of the herd. Vaccination of already infected animals also helps scabs to fall off quicker.

The best time to vaccinate ewes is 8 weeks before kidding so any lesions which develop in response to the vaccine will have healed before the kid is born.

Kids from contaminated ewes can also be vaccinated a couple of days after birth to try and prevent the virus from spreading to other areas of the body. Kids should then be given a second vaccination 8 weeks after the first.

Kids from vaccinated ewes will have some immunity via the colostrum but may become infected, showing fewer clinical signs.

Vaccines are available only from Onderstepoort Biological Products (OBP) at present.

The manufacture of vaccine by Grootfontein from farmers’ own virus-rich material has recently been halted due to legislation.

How is the vaccine administered?

The vaccine is not administered by injection in the usual manner but by using a thick needle on the clean area. Make 2 scrapes about 2.5cm long. The scrapes must be deep enough to make a red mark but not bleed. The vaccine is rubbed into the scraped region. A brush can be used for this. It is recommended that this is done in the axilla (armpit) NOT the inner thigh as infection could potentially spread to the udder and genitals.

A lesion develops within 7 days at this site. Always wear gloves as people can get the disease by being infected through abrasions of the skin when treating or vaccinating animals.

  1. Vitamin A supplementation,
  2. Good hygiene practices, making every effort to manage susceptible animals with as little stress as possible, and minimizing overcrowding will reduce the severity of outbreaks. 
  3. Good nutrition (avoid abrasive food types).

With the intensification of Angora goat breeding and grazing systems, the disease is becoming more prevalent on Karoo farms and having greater economic effects.

Dr Mackie Hobson

 

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