Demodicosis (Red Mange) in Dogs


Overview of Demodicosis (Red Mange) in Dogs

Demodicosis, also known as red mange or “demodex”, is a common skin disease of dogs caused by a microscopic mite called demodex canis. These mites are part of the normal flora of the skin, and are present in small numbers, so the disease is not contagious. In predisposed individuals the mites increase in number causing clinical disease.

Why some dogs develop demodicosis and others don’t is not understood. It is thought to be genetic; affected dogs have an immune system defect that may be inherited, making it difficult to keep the mites under control.

Types of Canine Demodex

There are different forms of this disease: localized and generalized.

Localized Demodex

This form usually occurs in dogs younger than one year of age. There is no breed or sex predilection. Affected animals are usually healthy and have developed demodicosis as the result of a temporary illness or a stressful event.

The first sign of localized mange might be thinning of the hair around the eyelids, lips, mouth and the front legs – a typical moth-eaten appearance. Prognosis is usually very good, and most animals (90 percent) will recover spontaneously. About 10 percent usually will become generalized.

Generalized Demodex

Generalized demodicosis can begin as a localized case or can present itself as an acute illness. It is frequently categorized according to the age of the dog during the initial onset (juvenile or adult). The main distinction between the two types is the result of differences in predisposing factors and prognosis.

  • Juvenile-onset generalized demodicosis has a more favorable prognosis. Most of them will “self cure” as their immune system matures, somewhere between eight months and three years, depending on the breed of the dog.
  • Adult-onset generalized demodicosis has a more guarded prognosis. These animals develop demodicosis as a consequence of another illness or immunosuppressive therapy. They do not have a genetic predilection for demodicosis. Conditions associated with adult onset demodicosis include cancer, endocrine disease, metabolic disease or steroid therapy. Prognosis depends on the underlying disease.

    For the generalized form, a genetically inherited predisposition to the disease has been found. For this reason, affected animals should be neutered. Both females and males have the same ability to transmit genetic predisposition to demodicosis. The generalized form of the disease is much more difficult to resolve with therapy and relapses after discontinuation of therapy are common.

  • What to Watch For

    Clinical signs consist of demodicosis consist of numerous patches that appear on the head, legs and trunk. These patches generally develop into large areas of hair loss, and the breakdown of skin leads to the formation of crusty sores.

    Diagnosis of Demodex in Dogs

    Demodicosis is diagnosed by the presence of symptoms and by performing deep skin scrapings on affected areas. The mites can be seen with the aid of a microscope. The mites are present on all dogs, so alone they do not constitute a diagnosis of mange.

    Treatment of Demodex in Dogs

  • Localized. If your dog has localized demodicosis, it is important to monitor him/her to establish whether the disease will stay localized or it will progress into the generalized form, as prognosis varies. You will be asked to bathe your dog using an antibacterial shampoo and apply a lotion on the affected area. Your pet will need additional scrapings to monitor the progression or regression of the disease every 2 to 3 weeks for 2 times.
  • Generalized. If your dog has juvenile onset generalized demodicosis you will be advised to neuter your dog. Demodicosis can be an expensive and frustrating disease to treat thus it is important not to contribute to its perpetuation.

    Treatment is necessary when disease is generalized. It includes the treatment of secondary bacterial infections and eradication of the mites. Eradication of the mites can be accomplished by using an amitraz-based dip (Mitaban®) or by using systemic medications (milbemycin and ivermectin). Depending on the breed of your dog, your veterinarian will select the most opportune therapy. Some therapies are not FDA approved (milbemycin and ivermectin) even though they are effective.

    It is very important that you closely follow the instructions of your veterinarian to minimize the likelihood of adverse effects. If the dip is used, your dog may need to be clipped to increase penetration and efficacy of this treatment. Adverse effects of the dip include excessive sedation, itchiness, tremors and coma. It is prudent to have your veterinarian dip your dog. After the dip, it is important for you to monitor for excessive sedation. If this occurs your veterinarian should be consulted, as there are medications that can help reverse this adverse effect. Also bathing will remove the residual medication present on the skin and hasten the recovery.

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