Two theories1 exist about why certain dogs develop demodectic mange, both of which deal with suppression of the immune system. While not proven to be inherited, most researchers believe the tendency to develop demodectic mange is hereditary, and most breeders seem to find evidence of certain families that are more prone to the problem. One theory regards the cause to be a defect in t- lymphocytes (a type of white blood cell) which respond to an immunosuppressive substance produced by the mites, resulting in a dog whose immune system cannot get rid of the mites. The second theory holds that it is not the mites, but a tendency to develop a bacterial infection along with the mange, which results in the bacteria suppressing the immune system. Either way, the result is the same, the mites and bacteria proliferate on the skin, causing hair loss, redness, etc.
Demodectic mange is seen primarily in two forms, juvenile and adult. Juvenile mange is further subdivided into localized and generalized mange. The age at the onset of symptoms determines the diagnosis, with mange beginning before about 15 months of age considered juvenile.
Localized juvenile mange is a common problem resulting in patches of hair loss, primarily involving the face and front legs, but which may be found anywhere on the body. The symptoms begin between three months and a year of age, and 90%2 of the dogs cure themselves within 4-8 weeks. The remaining dogs progress on to have generalized mange, which is characterized by more than 10 areas of hair loss, itching, bacterial infection and redness.
Adult onset mange is that which begins in dogs more than about two years of age, and is not considered hereditary. Many dogs with adult onset of mange have an underlying health problem that is suppressing the immune system and leads to the development of the mange. A dog with adult onset of mange should be carefully examined and have lab work performed to rule out any underlying cause.
Diagnosis of demodectic mange involves finding a large number of mites in affected areas. The skin is scraped with a scalpel blade and the resulting material is examined under the microscope. A skin scraping is a simple, inexpensive test and should be performed on every dog with hair loss of any description in order to rule out mange as a cause.
Treatment varies with the severity of the symptoms. As localized mange will resolve even without treatment, most veterinarians regard treatment for localized mange as a case of treating the owner, rather than the patient. Treatment may involve regular bathing to clear the hair follicles, application of insecticidal ointments to the affected areas, or antibiotics. There is no evidence that spot treatment of localized lesions will prevent generalized mange. It is not considered advisable to treat localized mange with amitraz (Mitoban ) dips.3 In many cases, no treatment at all is the best treatment, with periodic visits to the veterinarian for scrapings to determine if the numbers of mites are increasing.
Generalized mange, either juvenile or adult onset, is a serious and potentially life threatening disease, as unresponsive cases sometimes require euthanasia. Treatment of generalized mange should only be undertaken with the knowledge that it will probably take a long time, be expensive, and may not work. Adult onset is particularly difficult to treat, due the common presence of another underlying condition.
Treatment of generalized mange usually involves clipping the hair to better reach the skin, bathing with antibacterial shampoos, regular dipping with amitraz (Mitoban ) and appropriate antibiotics. Many individuals will relapse if not treated every eight weeks or so, even after an apparent cure. Many animals treated with amitraz develop side effects, most notably sleepiness and depression. While frightening to owners, these are rarely serious. Due to the presumed hereditary nature of the disease, the American Academy of Veterinary Dermatologists recommends the surgical neutering of any animal affected with, or recovered from, generalized demodectic mange.
In cases which do not respond to amitraz, some success is being obtained with milbemycin or ivermectin, oral heartworm preventives, but this requires daily treatment, and these drugs are not approved for this use. Some researchers feel higher concentrations of amitraz, used more frequently, may also help, although these doses are not approved in this country.
Thyroid hormone is not indicated unless the animal is hypothyroid, as well as having mange. Corticosteroids (cortisone) should not be given even if the animal is experiencing itchiness, due to the immunosuppressive effects of these drugs.
Juvenile demodectic mange is a common problem in Italian Greyhounds. Data from the IGCA health survey indicates some 10% of IG’s have had localized mange. Only about 5% of the affected individuals went on to develop generalized mange, a somewhat lower figure than might be expected. What conclusions can we draw from this information? Probably that while localized mange is a common problem in IG puppies, most dogs do not develop generalized mange. This would seem to indicate that removing these animals from a breeding program would serve no purpose, but conversely, due to the relative infrequency of generalized mange, any affected individual should be surgically neutered.
1.Henfry, JI. Canine Demodicosis Update. In Practice September 1990 187-192
- Foley, RH. Parasitic Mites of Dogs and Cats. The Compendium Vol 13, 5 p.783-786
- Muller, GH Kirk, RW Scott, DW. Small Animal Dermatology. 1989 W.B Saunders Co. Philadelphia PA
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