Sheep-scab is a condition in sheep caused by infestation with a particular type of mite (Psoroptes ovis, known as the sheep-scab mite). This mite is a very small, wingless parasite that you can barely see with the naked eye, and then only properly under a magnifying glass or a microscope.

Sheep-scab is also known as scab, psoroptic mange or “brandsiekte” in South Africa. Because sheep-scab is severe and spreads easily, it is a controlled disease in South Africa. The disease occurs all over Sub-Saharan Africa.

We thank the Department of Agriculture, Forestry and Fisheries of the Republic of South Africa for distributing this vital information on animal diseases.

Why is sheep-scab important?

Sheep-scab remains a very significant health and welfare problem for the sheep industry. It hampers the efficiency of sheep farming and reduces profitability in the sense that it causes a loss in wool production. Other production costs include loss of meat, milk, leather and reproductive capacity. It spreads through contact and can even cause the death of sheep. It is also costly to treat and to control.

How do sheep get sheep-scab?

The mites causing sheep-scab spend most of their life on sheep, and sheep are therefore infested by close contact with other sheep that have scab. This can occur by the introduction of infested sheep to your flock, or by contact of your sheep with infested sheep from other flocks (for example, during grazing or at shearing).

Note that sheep may not always show signs of disease when infested with mites (particularly short-wooled breeds such as Dorpers).

Close contact most frequently occurs when the sheep are kraaled or housed in other ways (for example, in shearing sheds). The mites can drop or be rubbed off the sheep and survive for up to ten days, so that other sheep can be infested by mites in kraals, other premises, auction yards, pastures, or on wool that has been rubbed off infested sheep. Sheep-scab most frequently occurs in autumn and winter.

What are the signs of sheep-scab?

• After piercing the skin with their sharp mouthparts, the mites feed by sucking moisture from the tissue below the skin, which results in irritation and itchiness of the skin.

• The earliest sign is ragged-looking wool because the sheep are itchy and bite and scratch themselves. If you inspect the sheep carefully, you may feel very small lumps on the skin.

• You will also notice the sheep biting themselves and rubbing against fences and other objects.

• You may see wool in the mouths of the sheep and wool may also be found on fences and other objects against which the sheep rub.

• Fluid leaks from the irritated skin, and dries to form yellow crusts or scabs. This is why the condition is called scab.

• You will see bare, scabby patches and matted wool.

• The affected areas get larger over time as the mite numbers increase, which can lead to a loss of wool over large areas.

• The mites prefer areas covered with wool, particularly on the sides of the sheep.

• They tend to occur on the shoulders and sides of woolly sheep, and the tails and backs of hairy breeds.

• The biting and scratching aggravate the condition, and bacterial infection can result.

• If sheep are left untreated, they can become very thin and weak and eventually die.

Remember, one scab-infested sheep can result in the re-infestation of your entire flock!

How can you tell if your sheep have scab?

• By the above signs observed in sheep.

• Any itchy sheep must be suspected of having sheep scab!

• As it is difficult to see the mites with the naked eye, a definite diagnosis requires skin scrapings and looking for mites under a magnifying glass or microscope. The mites live under the scabs, and are best found on the edges of the scabs. Collection and identifi cation of mites can be done by your animal health technician or state/private veterinarian.

• If you suspect your sheep to have sheep-scab, you are legally obliged to immediately notify your state veterinarian or animal health technician.

• He will prescribe the required treatment of the aff ected fl ock.

• Eradication involves the quarantine of the premises and dipping of all sheep on the farm.

How can sheep-scab be prevented?

• Previously, yearly dipping of sheep to control sheep-scab was compulsory. This is no longer so, and the emphasis is on recognising infested flocks and controlling infestations when they are identified.

• You should be careful when introducing new sheep into your flock. Check that they do not have scab.

• Dip all introduced sheep with a dip effective against sheep-scab mite before they come into contact with your sheep.

For further information, contact your nearest animal health technician or state/private veterinarian, or visit the website of the Department: Agriculture, Forestry and Fisheries Republic of South Africa at www.daff.gov.za.