Demodectic mange (also known as red mange, follicular mange, or puppy mange) is a skin disease, generally of young dogs, caused by the mite, Demodex canis or Demodex injai. It may surprise you to know that demodectic mites of various species live on the bodies of virtually every adult dog and most human beings, without causing any harm or irritation. These small (0.25 mm) ‘alligator-like’ mites live inside of the hair follicles (i.e., the pore within the skin through which the hair shaft comes through), hence the name follicular mange. In humans, the mites usually are found in the skin, eyelids, and the creases of the nose.

Disease related to suppressed immune system

Whether or not Demodex causes harm to a dog depends on the dog’s ability to keep the mite under control. Demodectic mange is not a disease of poorly kept or dirty kennels. It is generally a disease of young dogs that have inadequate or poorly developed immune systems or older dogs that are suffering from a suppressed immune system.

What is the life cycle of Demodex canis?

The demodectic mite spends its entire life on the dog. Eggs are laid by a pregnant female, hatch, and then mature from larvae to nymphs to adults. The life cycle is believed to take 20-35 days.

How is Demodex canis transmitted?

The mites are transferred directly from the mother to the puppies within the first week of life. Transmission of the mites is by direct contact only. That is, the mother and puppy must be physically touching, as parasite cannot survive off of the animal. This is important because it means the kennel or bedding area does not become contaminated and therefore the environment need not be treated. Lesions, if present, usually appear first around the puppy’s head, as this is the area most in contact with the mother. Virtually every mother carries and transfers mites to her puppies. Most puppies are immune to the mite’s effects and display no clinical signs or lesions. A few are not immune and it is these puppies that develop full-blown cases of mange.

What are the signs of demodectic mange?

Individuals that are sensitive to the demodectic mites may develop a few (less than 5) isolated lesions (localized mange) or they may have generalized mange, in which case, there are more than 5 lesions involving the entire body or region of the body. Most lesions in either form develop after four months of age.

The lesion and signs of demodectic mange usually involve hair loss; crusty, red skin; and at times, a greasy or moist appearance. The mites prefer to live in the hair follicles, so in most cases, hair loss is the first noted sign, Usually, hair loss begins around the muzzle, eyes, and other areas o the head. The lesions may or may not itch. In localized mange, a few circular crusty areas will be noted, most frequently on the head and forelegs of young dogs 3-6 months of age. Most of these lesions will self heal as the puppies become older and develop their own immunity. Persistent lesions will need treatment that will be described later. In cases in which the whole body is involved (generalized mange), there will be areas of hair loss over the entire coat, including the head, neck, abdomen, legs, and feet. The skin along the head, side, and back will be crusty and oftentimes inflamed. It will often crack and ooze a clear fluid. Hair will be scant, but the skin itself will often be oily to the touch. There is usually a secondary bacterial infection. Some animals can become quite ill and develop a fever, lose their appetite, and become lethargic. Patients with generalized demodectic mange need immediate vigorous treatment.

How is demodectic mange diagnosed?

Once Demodectic mange is suspected, it can usually be confirmed by a skin scraping or biopsy, in which case, the mites can be seen with the aid of a microscope. They are too small to be seen with the naked eye. The adults appear as tiny, alligator-like mites. Remember that these mites are present in every dog, so by themselves, they do not constitute a diagnosis of mange. The mite must be coupled with the lesions for a diagnosis of mange to be made.
Older dogs diagnosed with demodectic mange should be screened for certain other diseases such as Cushing’s disease, hypothyroidism cancer and heartworm disease. Nutritional history and any history of treatment with corticosteroids or other immune-suppressing drugs should be noted.

How is demodectic mange treated?

The treatment of Demodectic mange is usually accomplished with lotions, dips, and shampoos. Fortunately 90% of demodectic mange cases are localized, in which only a few small areas are involved and can often be treated topically. A treatment that has been successful for years has been a 1% rotenone ointment (Goodwinol ointment), or more recently, a 5% benzoyl peroxide gel applied daily. Bathing periodically with a benzoyl peroxide shampoo and feeding a high quality diet and a multivitamin with a fatty acid may also help some dogs. Most of these localized lesions will heal on their own and do not require overly aggressive treatment, though they may worsen before they improve.

If a dog develops generalized demodicosis, more aggressive treatment is usually required. Studies show that between 30% and 50% of dogs that develop the generalized form will recover on their own without treatment, but treatment is still always recommended for the generalized form. Treatment can be lengthy and expensive. The treatment of choise continues to be Amirtraz dips applied every two weeks. Amitraz is an organophosphate, and is generally available under the product name Mitaban. It is a prescription product and should be applied with care. Humans should always wear rubber gloves when applying it to their dog, and it should be applied in an area with ventilation. It is recommended that medium-length and longhaired dogs be clipped short, so that the dip can make good contact with the skin. Prior to dipping, the dog should be bathed with a benzyol peroxide shampoo to help remove oil and cellular debris.

Most dogs with generalized demodicosis require between 4 and 14 dips given at 2 week intervals. After the first three or four dips, a skin scraping should be performed to determine if the mites have been eliminated. Dips should continue until there have been no mites found on the skin scrapings taken after 2 successive treatments. Dogs should not be considered “cured” until one year after their last treatment.

Some dogs develop sedation or nausea when dipped, and toy breeds in particular are sensitive to amitraz. Half strength dips should be used on these sensitive animals.