Dry, flaky skin in pigs: It could be sarcoptic mange
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A scratching pig could be suffering from sarcoptic mange. Vet Liz Bennett explains how to identify it and what treatment will be required
A lot of pet pigs, especially older ones, have skin that is scurfy and flaky. It can even look like it is cracking. This is often simply dry skin where low humidity has dried out the external layers. If a pig seems particularly itchy, though, this could mean a more serious problem. Sarcoptic mange is caused by a mite (Sarcoptes scabiei var suis) that lives in the skin. It is a host-specific mite that is spread from pig to pig by direct contact or contact with recently contaminated surfaces. It can persist in the environment for up to three weeks in ideal conditions, so bear this in mind if transporting your pig or sharing equipment. These microscopic ectoparasites will cause rough, scaly skin and the pig will be very itchy, which will lead to red, inflamed areas that can bleed.
It usually starts behind the ears, but then spreads across the body. Head shaking can be persistent and may lead to secondary ear damage, such as aural haematomas (large blood blisters within the ear flap). Pigs can also become hypersensitive to the mites (usually 3-8 weeks after the initial infection), causing small red pimples that will cover the entire body.
As the disease progresses, chronic lesions will occur with thick encrustations in the ears, behind the elbows and on the hind legs. It is not just skin signs that are seen with mange; because of the irritation, aggression may also be a feature, including tail, ear and vulva biting. Chronically infected boars may fail to work due to discomfort causing infertility. Growth rates can decline by up to 15% and feed usage in heavily infested sows will be increased by 10% or more.
Diagnosis is confirmed by demonstrating the presence of the mite. A teaspoon scraping from the inside of the ear can be a productive site. There is also a blood test available. The mite does not survive on humans.
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The most effective treatment is an injectable Avermectin, such as panomec/ivomec, and several injections every 2-3 weeks may be required. All pigs in the group will require treatment. Topical products are no longer licenced, although there is an 'in feed' treatment available which has a shorter meat withdrawal period.
It can be difficult to eradicate. Cleaning the environment should be a part of the control programme, with surfaces disinfected and then left to dry to assist with the killing of the mite adults, eggs and larvae. Leaving open ground unoccupied for a month — particularly in the summer — will lead to dying off of the skin parasites, and treating prior to reoccupation may be sufficient to break the cycle of infection.
To prevent reinfection, isolate incoming stock for a minimum of six weeks. Isolate and treat any pigs that have had contact with outside animals. If in doubt, treat twice during the isolation period.
Is it lice?
The other possible parasitic cause of itchiness is lice (Haematopinus suis). These are visible to the naked eye and are usually seen around the head and neck and between the legs. Eggs laid on the hairs develop into adults over a four-week period, but the louse is dependent on the pig and can only survive a few days off the body. However, the eggs can survive for a few weeks in the bedding. Since louse eggs are unaffected by ivermectin and may take up to three weeks to hatch, retreatment is nearly always necessary.
Parasitic skin disease can be very debilitating and severely affects welfare and productivity, so take the time to look after your pig's skin and keep it healthy.
Liz Bennett is a vet with Didcot-based Larkmead Vets, one of the largest pig practices in the UK. Its expert team of vets provides specialist advice on all aspects of pig health and management