Demodex mange is a very itchy skin condition caused by a mite named Demodex canis. Most dogs are infected as puppies while they are nursing. The mites live in the hair follicles and sebaceous glands on the skin. Many dogs will have mites without showing any clinical signs. In some dogs thought to be immuno-compromised, the mites cause an inflammatory response in the skin that makes the dog miserable. Their hair falls out revealing flaky skin. If not treated early, the hair follicles will rupture creating a condition called furunculosis (boils). Dogs with furunculosis often have secondary bacterial and/or yeast infections that can become life-threatening.
Treatment of demodicosis is tailored to the patient. Most dogs with localized disease which means one or two areas of hair loss, will clear the disease on their own. I still recommend treating these dogs just to be safe. Dogs with generalized disease require aggressive therapy to kill the mites as well as get rid of any secondary infections. Dogs are dipped in Mitaban (19.9% amitraz) every two weeks until the mites are eradicated. The dips are usually done at a veterinary hospital to observe and treat the side effects of this drug. Patients are monitored for hypothermia, lethargy, diarrhea, swelling and an abnormally slow heart rate. Mitaban is the only FDA approved drug for demodex in dogs.
For non-herding breeds, ivermectin can be used to treat demodex. The patient is started at a low dose and then gradually increased if no problems are encountered. Again, I want to warn people not to use ivermectin in herding breeds and any mixes as death may result due to the multiple drug resistance gene mutation. Side effects of ivermectin include disorientation, blindness, problems walking and coma. Milbemycin is an alternative to ivermectin but has the same warning against use in herding dogs as well as dogs under 12 weeks of age.
Unfortunately, none of the treatments will work in all dogs. I have had the best luck with the Mitaban dips when they are done properly. The common mistakes I observe are: 1) Using old solution 2) Dipping dogs with long hair. I always keep these dogs clipped to allow good contact between the dip and the skin. 3) Using too little dip. The dog’s paws should soak in the dip for 15 minutes while additional dip is being continually poured over them. Think of it as basting. 4) Allowing the dogs to swim after a dip. All of the skin, including the paws must be kept dry between treatments. Place booties or plastic bags over the paws to prevent contact with snow and wet grass. 5) The most common mistake of all the treatments listed above is stopping too soon. Treatment must continue for 1 to 2 months after no mites are observed on two skin scrapes performed 1 month apart. Because dogs with generalized demodicosis are thought to be immune-compromised, boosting the dog’s immune system would be helpful. Unfortunately, I have not been able to find any immune-stimulants that help.
-Kwochka, KW. Canine and Feline Demodicosis Treatment Options. Western Veterinary Conference Proceedings 2004.
-Shell, L. Demodicosis Associate Database, Veterinary Information Network, 12/20/2008.