African Horse Sickness (Perdesiekte)


Since summer is on its way the usual parasites and diseases are as well. Certainly one of the most feared equine diseases is African Horse Sickness.
The vector (insect that spreads the disease) is a midge. Horses that spend time outside during the night and graze in low lying areas or near streams or dams are at risk.
The disease presents in four forms:
  • Dikkop,
  • Dunkop,
  • Mixed Form and
  • Horse Sickness Fever
Dunkop is the most aggressive, mixed form the most common and Horse Sickness Fever the mildest form of the disease. The primary problem of the condition is an inflammation of the blood vessels which causes fluid leakage into the subcutaneous(under the skin) space in the case of Dikkop and into the lungs in case of Dunkop.
There is no effective treatment for African Horse Sickness, only palliative treatment, which means that only the symptoms can be treated and the horse made comfortable. Since it is a viral disease the horse has to eliminate the virus itself.
The only way to fight the disease is to try and prevent it from occurring. This is most effectively done by vaccinating the horses with the African Horse Sickness (AHS) vaccine. It is very important that both doses are given three weeks apart as there are seven different types of Horse Sickness and they are split between the two doses. Limiting exposure to midges is an important management tool in aiding prevention of the disease. This can be done by stabling your horse between dusk and dawn when midges are most active, using insect repellents, using a day blanket during the day and having other animals like cattle graze with the horses. Early detection of the disease is important and can be done by taking the horse’s temperature twice daily (am and pm) where you will be looking for a dramatic rise in temperature. Other diseases (ex. tick fever) could also cause a rise in temperature.
Other diseases that may have similar symptoms are Equine Viral Encephalosis and West Nile Virus (WNV). Blood tests can distinguish between these diseases; the Equine Research Centre at Onderstepoort does one of the AHS tests free of charge while funds are available. All three diseases occur in the Parys area. The more samples are tested the more we have an idea of what diseases occur in certain areas and the more the efficacy of AHS vaccine can be tested in the field as well as motivating the industry to make WNV vaccine freely available.
The best way to prevent Horse Sickness is vaccination!
Please ensure that you order and get your vaccine early in the season (ie now) before any outbreak occurs and stock runs out. Please remember to maintain the cold chain ie keep the vaccine refrigerated at all times until the vaccine is used. Never put the vaccine in the freezer. Once the vaccine has warmed up it must be discarded; recooling is not effective.
Please contact Dr. Johan Venter at Parys Dierehospitaal on 056-8112114 if you have any questions.


Horse Castration


Even though winter is almost over (thank goodness) there is still enough time to get your stallion castrated. The reason why we prefer winter is that flies are less thus chance of fly strike and infection.
The procedure usually involves heavily sedating the horse or if the horse is very fractious, performing a short anaesthesia. The scrotal skin and testis are locally anaesthetised and two incisions made to remove the testis, the incisions are not closed. The horse is given a once off antibiotic and anti-inflammatory treatment. A tetanus vaccination is also administered.
Post-operative care involves walking the horse and doing some hydrotherapy to promote drainage of the surgical site. If proper drainage does not occur complications can occur such as seroma formation and infection.
Some of the reasons for electing to castrate a stallion are:


  • For ease of controlling the animal, geldings are usually much more docile than stallions and are not influenced by mares on heat.
  • If the horse is to be used for sporting events, a stallion’s neck tends to become large and muscled which negatively influences their sporting ability (ex. endurance).
  • If there is no need for a stallion on the property, stallions tend to be quite aggressive towards other horses and thus need to be kept alone.
  • If a colt is castrated before his growth plates close the horse will grow taller than he would have if he stayed a stallion. This is due to the effect testosterone causing growth plates to close earlier.
  • Unwanted matings would not occur.


Please contact Parys Animal Hospital on 056-8112114 if you have any questions or would like to make an appointment.
Kind regards,
Dr. Johan Venter (B.Sc. (vet.biol.), B.V.Sc.)

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