Pig Mange: how to spot it and how to treat it
The warm spring, coupled with a mild winter will result in earlier activity of flies, ticks and midges this year. All of these can be transmitters of disease, as well as causing disease themselves. Pigs like to scratch; they have naturally dry skin. However, if your pigs seem particularly itchy, there could be 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. These microscopic ectoparasites will cause rough, scaly skin and your pig will be very itchy leading to red inflamed areas that can bleed. It usually starts behind the ears, but it then spreads across the body. Head shaking can be persistent and 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 intense skin reactions of small red pimples covering their entire body. As the disease progresses chronic lesions will occur with thick encrustations in and behind the ears, behind the elbows and on the inside of the hind legs. It is not just skin signs that are seen with mange; because of the irritation, aggression may also increase, resulting in 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 for examining under the microscope. There is also a blood test available. The mite can affect people, but they do not survive on us as we are a dead end host.
The most effective treatment is an injectable Avermectin (such as Panomec/Ivomec) which is available on prescription. Because of the life cycle of the mite, several injections every 2-3 weeks may be required. You must also remember to treat all the pigs in the group. Topical products are no longer licenced, although there is an ‘in feed’ treatment available which has a shorter meat withdrawal period.
Mange can be very difficult to eradicate, especially when pens and shelters are permanently occupied. Cleaning the environment should be part of the control programme, with surfaces washed and disinfected, and then left to thoroughly dry to assist killing of the mite adults, eggs and larvae. Leaving open ground unoccupied for one month – particularly in the summer will lead to dying off of skin parasites and treating prior to reoccupation may be sufficient to break the cycle of infection.
To prevent re-infection, it is important to isolate incoming stock for a minimum of six weeks. Isolate and treat any pigs that have had contact with outside animals such as at shows or where boars are shared. If you are in doubt, treat twice during the isolation period.
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. The eggs can survive for a few weeks though in the bedding. Injectable Ivermectin will kill the adults but, as with the mites, since the 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. If you think you may have a problem on your farm, do not hesitate to get in touch.