Demodectic Mange

DISEASE RELATED TO SUPPRESSED IMMUNE SYSTEM

Whether or not Demodex causes harm to a dog depends on the animal'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 [1] or older dogs that are suffering from a depressed 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 the 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 that develop into full-blown cases of mange.

What are the signs of demodectic mange?

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

The lesions 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. Sometimes hair loss begins around the muzzle, eyes and other areas on the head. In localized mange, a few circular areas will be noted, most frequently around the head and muzzle. These areas may be crusty or more commonly, they may just be areas with thinning hair. These 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 often times 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. 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 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.

How is demodectic mange treated?

Treatment of demodex traditionally consisted of Mitaban dips (every 2 weeks for 3-6 dips), daily oral medication, shampoos, lotions, and/or immunostimulant therapy. Dips are generally done by your veterinarian, and some dogs can have reversible reactions to the amitraz in the Mitaban dip. Luckily, there are newer flea/tick treatements which can be used to treat demodex, although these treatments are off-label. We primarily use Nexgard or Bravecto to treat uncomplicated demodex. With severe demodex, other treatments may also be used.

Dogs that have generalized demodicosis often have underlying skin infections so antibiotics are often given for the first several weeks of treatment. Because Demodex flourishes on dogs with a suppressed immune system it is wise to check for underlying causes of immune system disease, particularly if the animal is older when they develop the condition.

PROGNOSIS AND IMPACT ON BREEDING

Demodectic mange is not an inherited condition but the suppressed immune system that allows the puppy to be susceptible to the mites can be. Remember that all puppies receive the mites from their mother but only a few have ineffective immune systems and develop the mange. This sensitivity can be passed genetically through generations. Individuals that have a history of demodectic mange, and their parents and siblings, should not be bred, and should be spayed or neutered by six months of age. Through careful breeding most cases of generalized Demodicosis could be eliminated. The various species of Demodex mites tend to infest only one species of host animal, i.e., Demodex canis infests dogs, Demodex bovis infests cattle, and Demodex folliculorum infests humans.

Can I get Demodex from my dog?

The various species of Demodex mites tend to infest only one species of host animal, i.e., Demodex canis infests dogs, and Demodex bovis infests cattle. This means your dog cannot pass on demodex to you.

CONCLUSION

In conclusion, a few important points should be repeated. The mites are transferred from the mother to offspring in the first few days of life. The first sign of hair loss usually does not occur until after four months of age. Demodectic mange is almost always curable or controllable with persistent treatment except in rare cases with very immune suppressed individuals. The immune system condition that allows for the development of demodectic mange can be an inherited condition and breeding of these animals should not occur.