Susan Kerr, DVM
February 12, 2016

My pigs have mites. What can I do to treat the mites themselves and the pigs’ skin damage, and how can I prevent future infestations?

First, we need to clarify if you are in the middle of a “lousy” situation or have a “mitey” big problem instead. People often confuse mites and lice, but once you learn the difference, it’s easy to tell them apart: We can see lice with the naked eye but need a microscope to see mites. Mite infections can be diagnosed via skin scrapings and microscopic examination, skin biopsy or even response to treatment, while a hog-lice infestation can easily be diagnosed by examination of the pig’s skin. Pigs can even be infested with both parasites at the same time.

Lice Vs. Mites

Unlike the lice of other livestock that tend to be troublemakers during winter, hog lice seem perfectly happy to be a problem in the summer, as well, and mites can be a problem any time. Both parasites have life cycles that ­occur entirely on the host. They spread ­primarily through contact with infected animals and through ­infected bedding or habitat. If you didn’t have a problem and now you do, odds are you brought in an infected ­animal or your pigs came into contact with one.

Microscopic mange mites burrow into a pig’s skin, laying eggs along the way and causing inflammation and itchiness in the host. The eggs hatch within a few days; the entire cycle from egg to egg-laying adult is completed in about two weeks. Although the majority of mites and eggs remain on the host, some can contaminate the environment, particularly bedding. Mites can live many days in the environment but die in just a few days when warmer environmental temperatures exist. All animals in contact with one another and/or having access to the same environment should be treated at the same time; a second and possibly third treatment will be needed to kill the mites that develop after the first treatment. Wait a week after treatment before moving pigs to uninfected facilities or allowing them to co-mingle with ­uninfected swine. Permethrins can be applied to the environment to kill mites in the environment, but they will also kill beneficial insects, so use caution.

Hog lice are large for lice—adults are 1/4 inch long—and dark; they prefer to hang out on the underside of a pig’s body and in armpits, folds of skin and ears. They can also be seen, moving on the head and back of affected animals or attached and sucking blood. Adult female lice lay eggs called nits, which are firmly attached to the host’s hair and ­easily observed.

Depending on environmental conditions, eggs hatch in two to three weeks and the life cycle is complete in another two weeks. The entire life cycle takes place on the affected animal, as lice can only live a few days without a host. Like mites, lice ­irritate their host, causing itching, reddened skin, secondary skin injuries, anxiety and weight loss; they can also transmit some diseases. Also as with mites, a second or even third treatment will be needed to kill nymphs and adults that hatched and developed from eggs after the first treatment.

Treating Pig Lice and Mites

Over-the-counter meds are available for treatment of lice and mange in swine. Injectable ivermectins and topical permethrins are effective against both parasites when used according to label directions. Note that treated swine shouldn’t be slaughtered sooner than five days after treatment with permethrin or 18 days if an ivermectin product is used. Always follow medication label instructions regarding slaughter withholding times and dosages.

Unless secondarily infected, your pigs’ skin should heal readily after you kill their parasites and they stop excoriating themselves while scratching. Clean significant scratches and wounds with a livestock disinfectant soap twice daily, rinsing well. Consult a veterinarian if any sores or injuries persist. Avoid applying topical medications because most interfere with healing instead of hasten it. Using an ­approved fly spray will help keep flies from bothering unhealed lesions.

If possible, remove infected pigs’ bedding and leave the area vacant for several weeks before putting down clean bedding and housing pigs there again—the longer, the better. If you have successfully treated all infested pigs, retreated once or twice, removed bedding, and given any mites or lice in the environment time to die, you should be able to put this episode behind you.

Prevent Another Infestation

To reduce the chance of re-introducing lice or mites into your herd, keep a closed herd or examine herd additions closely for obvious lice and the irritated skin, sores and itching typical of mange mites. Your veterinarian may recommend preventative mite treatment for herd additions to be on the safe side. However, bear in mind that every use of an ivermectin product for external parasite control hastens the development of internal parasite resistance to this family of dewormers. In most herds, ivermectins are still very effective against internal parasites of pigs, so don’t jeopardize this effectiveness by overusing them to control external parasites. Use topical permethrins first, as long as they are effective.

This is a good time to plug quarantine pens: Routinely isolate herd additions for one to three months downwind and downstream from the main herd, watching for any evidence of disease development or ­expression of parasite problems. If you live in an area with feral hogs, go to great lengths to prevent any contact or environmental overlap between them and domestic pigs, as they can transmit mites, lice and more serious problems to your herd.

About the Author: Susan Kerr, D.V.M., Ph.D., P.A.S., is a Wash­ing­ton State University Northwest Regional Livestock and Dairy Extension Specialist.

Article vetted by Dr. Lyle G. McNeal.


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