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Pay attention to orf in your flocks

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Estimated reading time: 4 minutes

  • The orf virus is a member of the parapoxvirus genus in the poxvirus family and infects the skin and mucosa of animals.
  • The virus has no specific preferences and affects all small stock, including ewes and rams.
  • Most infections occur when groups of sheep crowd together, for example in feedlots or in pens where they lamb or are classed.
  • Vaccination is the best method for preventing an orf virus infection in the flock.
  • To prevent the virus from infecting sheep and goat flocks, producers are advised to increase biosecurity measures on their farms.

Some of our readers may have treated or heard of sheep or goats that have been infected with orf (vuilbek). The orf virus is a member of the parapoxvirus genus in the poxvirus family and infects the skin and mucosa of animals. Orf is commonly seen in sheep, goats and especially young animals. It can lead to a serious bacterial infection if not managed properly. It can also be transmitted to people who have handled infected animals and form red or blue lesions on the fingers, hands, forearms and face. In humans it can be treated with antibiotics, but what to do if your animals are infected?

Dr Freddie Strauss, a veterinarian at the Hertzogbrug Animal Clinic in Aliwal North, sheds some light on the subject.

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Epidemiology

The virus has no specific preferences and affects all small stock, including ewes and rams. “Transmission occurs through direct contact or scabs that fall off due to new skin forming underneath it. The virus can be transmitted when other sheep or goats come into contact with these scabs,” says Dr Strauss.

“Most infections occur when groups of sheep crowd together, for example in feedlots or in pens where they lamb or are classed. While ewes can transmit the virus during lambing, newborns can also easily be infected when they suckle ewes that have lesions on their udders.”

While ingesting feed with small stems in it, it can cause abrasions on the skin around the mouth. These abrasions then serve as a breeding ground for the virus. Dr Strauss says that when goats feed on spiny and prickly shrubs, it can induce higher rates of infection.

“We also find that young animals grazing on green pastures where there is plenty of moisture in the soil, can develop a softening of the skin just above the hoof. This can cause wounds in the coronary band, as well as lesions which are restricted to the coronet of the hoof (the upper limit of the hoof capsule).”

There is always a chance of contracting orf where lambs have a suppressed immune system. Morbidity rates in affected flocks can reach between 50 to 100%, while the mortality rate ranges between 20 to 50%.

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Treatment

While wearing protective gear, one can carefully remove the scabs with a brush, causing the lesion to bleed and thus heal faster. Dr Strauss advises to then apply iodine spray or healing ointment to the lesion once the scab is removed, to help prevent a skin infection.

It is preferable to also inject the infected animal with Duplocillin (1ml per 20kg) to prevent secondary infections.

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Prevention

Vaccination is the best method for preventing an orf virus infection in the flock. According to Dr Strauss, an autogenous vaccine can be produced to isolate and destroy micro-organisms and boost the animal’s immunity. This can only be done by a veterinarian.

Pregnant ewes that have been vaccinated do not pass immunity to their lambs through colostrum. It is therefore best to vaccinate lambs at one month of age and give them a booster dose two months later. It is important to keep the vaccinated lambs and ewes apart from the rest of the flock, until all vaccine reactions have cleared up.”

To prevent the virus from infecting sheep and goat flocks, Dr Strauss advises producers to increase biosecurity measures on their farms. “For example, one can isolate newly introduced ewes and lambs from the rest of the flock and keep them isolated for at least three weeks thereafter. Examine these animals daily for clinical signs of orf. “The same applies when you want to sell your ewes at an auction. You should examine each one beforehand for scabs around the mouth and udders.” – Carin Venter, Stockfarm

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