By Roelof Bezuidenhout
Sheep scab, or brandsiekte, a skin disease caused by the sheep scab mite (Psoroptes ovis), is a major threat to South Africa’s wool industry.
An infestation often starts unnoticed in a flock but it can rapidly escalate, compromising the wool clip and harming the health of the animals. Rams may refuse to mate, and lambs can struggle to nurse properly.
The sheep scab mite’s life cycle – from egg to adult – spans about 11 days. Adult mites chew through the skin and feed on the serum that seeps from the resulting wounds, which soon form scabby crusts.
Early signs of an infestation are when sheep start scratching, rubbing against fences, or biting and plucking out their wool.
The mite is microscopic and can only be identified by an expert using magnification. If your sheep are showing signs of irritation, it is best to consult a veterinarian – if left unchecked, the infestation can spread like wildfire, even to neighbouring farms.
The mite affects only sheep – and all breeds. It can survive for up to two weeks on goats, as well as on clothing, vehicles and wool scraps, and in pens. In summer, mites may lie dormant in the base of the horns or in the folds under the tail, only to flare up again in winter.
Treatment
If even a single sheep tests positive for scab, it must be reported to the state veterinary office. The farm will be placed under quarantine, and no livestock may be moved until the infestation has been brought under control. Thanks to modern treatments, ranging from dips to injectables, this is manageable, but it still requires time and money. Follow-up treatments are always necessary about 10 days later, and to prevent re-infection, all animals on the farm must be treated within a short timeframe.
As an added precaution, workers’ overalls should be regularly changed and washed during treatment periods. It’s also critical to double-treat any new animals brought onto the farm, including rams.
Make sure boundary fences are secure to keep out stray or roaming animals, and always disinfect shearing equipment when a shearing team arrives on the farm. Sheep scab can also spread via livestock shows and auctions, or by buying sheep from unscrupulous speculators.
Prevention
Keeping a farm free from sheep scab largely comes down to plunge-dipping, or injecting animals after shearing – a standard lice-control measure on most sheep farms. Plunge-dipping remains the most effective line of defence, provided the dip concentration is maintained correctly and each animal is fully emersed three times to ensure complete coverage. Syringes must also be routinely checked to ensure every sheep receives the proper dosage during injectable treatments.
The problem tends to escalate in areas where plunge-dipping is no longer regularly practised, often due to neglected or damaged dip tanks. Broken fences and poor flock management further contribute to uncertain animal health status in many districts. That’s why sheep scab is often referred to as an irresponsible – and entirely preventable – scourge.
The mite was widespread in the early 1900s, but a concerted government campaign to bring it under control was very successful. But without regular treatment of all flocks, new outbreaks remain a constant risk.
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 | Roelof Bezuidenhout is a fourth-generation wool, mohair, mutton and game farmer and freelance journalist. Attended Free State University, majoring in animal husbandry and pasture science. Other interests include agricultural extension and rural development. |
