Demodicosis (Red Mange) in Dogs

Demodicosis, also known as red mange, is an infestation of the dog by a variety of Demodex mite. Although they are found in a dog’s normal bodily flora, they are usually kept in check by the immune system. Immature or impaired immune systems may allow the mites to flourish and cause thickened scaly patches on the skin. Small, localized patches can be treated relatively simply, but Demodex infestations that have spread over extensive areas of the skin require more persistent and aggressive treatments to eliminate.

Demodicosis is the inflammation and thickening of the skin due to an overproliferation of a species of Demodex mite living naturally on your dog’s skin.

Most of the symptoms of this infestation show up on the skin of the canine that is affected. 

• Crusting
• Discoloration
• Infections
• Loss of hair
• Pustules
• Redness
• Scaly or leathery appearance
• Sensitive to touch
• Sores 
• Unpleasant odor
• Warm to the touch
• Wrinkling

In cases where the mites have invaded the lymph nodes, you may see additional symptoms such as fever, lethargy, and loss of appetite. 

Types

Demodicosis, also known as red mange, is caused by a species of Demodex parasite. Most dogs have some of these parasites living in the fauna on their bodies, generally in the hair follicles. The adult form of this parasite is shaped like a tiny cigar sporting eight short legs, although the larvae only have six legs. Three types of mite can contribute to this condition in dogs.  

Demodex canis - This is the most common form of Demodex and is just 40-300 microns long. 

Demodex cornei - This type of Demodex parasite is the smallest of these species to inhabit dogs, and are only half the length of the Demodex canis. 

Demodex injai - This variety is both the largest form of Demodex and the most recently found; outbreaks of the injai variety of Demodex are usually limited to the back and the hindquarters of the dog.

The Demodex mites that cause this disorder are tiny cigar-shaped lifeforms with eight short legs that are generally acquired from mother dogs to puppies during nursing or may be transferred during other physical contact, and they are often found among the other standard fauna on healthy dogs. The canine immune system usually keeps the mange in check, however, dogs with immature or compromised immune systems may develop this disorder. The susceptibility in puppies does appear to have a genetic component and dogs that have a history of developing demodicosis, as well as their parents and siblings, should not be bred.

When you bring your animal into the veterinarian's clinic, a sample of the skin affected by the mange will be taken for a process known as cutaneous cytology, where the skin sample is examined microscopically. The Demodex mites  are easy to see on most skin samples with a microscope, and when coupled with the skin reaction, diagnosis becomes elementary. Younger dogs who contract this due to the simple immaturity of the immune system often outgrow the problem when they reach maturity, however, adult dogs who acquire this disorder should be thoroughly evaluated as this disorder may be an early indicator that the immune system has been compromised. 

Diseases and disorders that can lead to an overgrowth of these parasites can include Cushing’s disease, hypothyroidism, and cancer, among others. Nutritional history and medications will often be re-evaluated at this time, as well as disorders due to dietary deficiencies or allergies, which can also make the skin more prone to developing this type of mange.

Localized symptoms of demodicosis often resolve spontaneously but may also be treated with topical insecticides to kill the mites and hasten healing. Generalized demodicosis, which has spread over the entire body requires more aggressive therapy to gain control of it. Medicated baths, usually containing a pesticide known as Amitraz, are most commonly used to kill the mites. These are generally repeated approximately every two weeks for at least six treatments, or until no mites are found after two successive treatments. Certain dogs are sensitive to the chemicals and may develop sedation or nausea. Canines that show these symptoms should have the dip reduced to half strength. 

Another alternative is to administer one of the dewormers Ivermectin or Milbemycin orally. These medications are often successful in treating red mange, but because of the high dosage required to eliminate the infestation they can be dangerous in their own right and should only be administered under close veterinary supervision. Ivermectin is particularly dangerous to Collie breeds and Collie mix dogs and should be avoided for Collies and similar breeds.

Prognosis is generally quite good for localized infestations of demodicosis, often being easily eliminated. Generalized demodicosis can be challenging to treat effectively. Recurrences of the disorder are common as are bacterial infections, and treatment is generally a lengthy process. If antibiotics are prescribed to help treat a bacterial infection, it is important to continue the antibiotics for the full measure of time that your veterinarian recommends in order to avoid a return of the infection. 

Supplements to stimulate the immune system may help stem the infestation by these mites, and there are a number of safe herbal remedies that can contribute to healing the skin, such as lavender, almond, and neem oils, and frequent oatmeal baths. Steroid and corticosteroid treatments for red mange should be avoided as they suppress the immune system, worsening the problem.