Demodectic Mange Treatment for Dogs
What is Demodectic Mange?
Mange caused by the Demodex canis mite is a relatively common skin disease in dogs. It is most frequently seen in puppies, though it does occur in older dogs on occasion. Demodex mites are normally found in the hair follicles of the skin of dogs, and they pass from the mother dog to her puppies in the first few days of life. Mange occurs when the immune system of the dog cannot keep the mite numbers in check. In puppies, a delay or defect in the development of the immune system, malnutritionLack of proper nutrition, caused by not having enough to eat, not eating enough of the right things, or being unable to use the food that one does eat. or other illness may compromise the immune system and prevent it from regulating the mite population. In older dogs, chemotherapy or other immunosuppressive problems may allow the Demodex mites to proliferateIncrease rapidly in numbers; multiply.. When mite numbers become excessive, hair loss and secondary bacterial infections occur. This disease is not contagious to humans or other animals in the house, including other dogs.
It can be classified as localized or generalized. Localized mange is typically defined as four or fewer small patches of hair loss with or without a superficial bacterial infection. Generalized mange involves significant hair loss with bacterial skin infections and can become life threatening.
How is it Diagnosed?
Mange is usually diagnosed by the microscopic examination of deep skin scrapings. This involves the veterinarian squeezing the skin to extrude the mites from the hair follicles and then scraping off the material with a scalpel blade or similar tool. The material is examined under a microscope to look for evidence of demodecosis—adult mites or their eggs or larvae. An alternative to the skin scraping is the trichogram. This involves plucking hairs from the lesions and examining them under a microscope. In some rare cases, skin biopsiesAn examination of tissue removed from a living body to discover the presence, cause, or extent of a disease. may need to be obtained to make a diagnosis. This is particularly true for lesionsA region in an organ or tissue that has suffered damage through injury or disease, such as a wound, ulcer, abscess, tumor, etc. involving the feet or in certain breeds of dogs, such as the Chinese shar-pei.
What is the Treatment for Demodectic Mange?
Demodectic mange generally has a good prognosisThe likely course of a disease or ailment.. Some cases of localized Demodex in young dogs may spontaneously resolve, especially if secondary bacterial infections are controlled and treated. Other cases of localized and all cases of generalized demodectic mange will require more involved treatment. It is imperative that the secondary bacterial infections be controlled. Superficial bacterial infections involves treatment with topical antibacterials, but more severe cases will require both topical treatment and systemic antibiotics.
There are a variety of medications available to treat the mange itself. One is an amitraz rinse that is applied weekly or biweekly. It tends to be more effective in the treatment of juvenile-onset mange than adult-onset. The use of amitraz can be labor-intensive and may have some side effects in small dogs. It is recommended that long-haired dogs have their coats clipped short before using.
Other medications your veterinarian may use for treatment are oral ivermectin given daily, oral moxidectin given daily, topical moxidectin applied weekly or injectable doramectin administered weekly. These medications are used off-label, meaning they are not approved by the FDA for the treatment of mange; however, they are approved for use for other diseases, and there are peer-reviewed studies to document their successful use for treating demodectic mange in dogs. Many of these medications may be better tolerated by your dog than amitraz. Some of the herding breeds of dogs, such as Collies, have a genetic mutation (known as the ABCB1 or MDR1 mutation) that may make them more susceptible to the toxic effects of some of these drugs. If you have a herding breed dog with demodectic mange, it is worth having your dog tested for the defect before starting therapy to determine which drugs will be safe to use as treatment.
Treatment can take several weeks to months depending on the severity of the mange. Skin scrapings should be performed regularly until two negative (no mites seen) skin scrapings are obtained one month apart. Therapy should continue for four weeks after the second negative skin scraping. It is also recommended that dogs that have had demodectic mange not be used for breeding because there is a genetic predisposition for developing mange. The heat cycle in female dogs can trigger recurrence of the mange as the hormonal changes can affect the skin’s immune system.
In general, puppies that develop demodectic mange, especially the localized type, have a good prognosis for full remission. Most cases of generalized mange, especially in puppies, will also resolve with appropriate therapy. Dogs who develop demodecosis as adults or who have mange in their feet will typically require longer courses of therapy, and in some cases, the mange may not ever completely resolve. These dogs will need life-long therapy to manage the problem and keep the skin lesions in check. Any adult dog with mange should be checked for underlying conditions that could be suppressing the immune system, such as thyroid disease, Cushing’s or cancer. The chronic use of immunosuppressive drugs, such as prednisone or cyclosporine, may also predispose a dog to mange.
Anytime you notice your dog losing hair or developing a skin infection, check with your veterinarian. Mange will most likely be on the list of things he or she will check for. If your dog does have the disease, there a variety of ways to treat it and ensure your dog’s continued good quality of life.
Lori Teller, DVM is a graduate of Texas A&M College of Veterinary Medicine and lives in Houston, Texas. She practices at Meyerland Animal Clinic.