DEMODICOSIS : Parasite Infection

Demodectic mange, also called "demodicosis," is parasite infection caused by a microscopic mite of the Demodex genus. Three species of Demodex mites have been identified in dogs: Demodex canis, Demodex gatoi, and Demodex injai. The most common mite of demodectic mange is Demodex canis. All dogs raised normally by their mothers possess this mite as mites are transferred from mother to pup via cuddling during the first few days of life. Most dogs live in harmony with their mites, never suffering any consequences from being parasitized. If, however, conditions change to upset the natural equilibrium (such as some kind of suppression of the dog's immune system), the Demodex mites may "gain the upper hand." The mites proliferate and can cause serious skin disease.

Demodectic mange (unlike Sarcoptic mange) is not contagious. Classically Demodex mites have been felt to only be transferable from mother to newborn pup. After the pup is a week or so old, it has developed enough immunity so that infection is no longer possible. In other words, after age one week or so, a dog will not longer accept new mites on its body.
It is not clear if some species of Demodex are more contagious than others or if some contagion is possible under certain circumstances. Isolation of dogs with even the most severe demodicosis is felt to be unnecessary. While there is still assorted theories about dog to dog transmission of Demodex mites, there is no question that mites cannot be transmitted to humans or to cats.
Mites live inside hair follicles -- a difficult place for miticides (chemicals that kill mites) to reach.Mites are a normal residents of dog skin; it is only in some individual dogs that mites cause problems.

THREE FORMS OF DEMODICOSIS
1: LOCALIZED
Localized demodicosis occurs as isolated scaly bald patches, usually on the dog's face, creating a polka-dot appearance. Localized demodicosis is considered a common puppyhood ailment and approximately 90% of cases resolve with no treatment of any kind. This is quite a contrast to generalized demodicosis as described below so it is important to be able to distinguish localized from generalized disease. It seems like this would be a simple task since localized demodicosis classically involves several round facial bald spots and generalized demodicosis involves a bald scaly entire dog; still, reality does not always fit into neat categories in this way. Localized disease does not involve more than two body regions. (One spot or two on the face and one spot or two on a leg would still qualify as localized even though the spots are not close together.) Localized disease involves no more than 4 spots total on the dog.
Treatment is not necessary or recommended for localized demodicosis but there are treatment options for people who simply cannot feel right about doing nothing. Goodwinol ointment, an insecticide, may be used daily to control localized demodicosis. Antibacterial gels are also used against localized demodicosis and associated skin infections. It is important to note that rubbing a creme or ointment on a demodicosis lesion can cause reddening of the lesion making it appear to get worse. It is also possible for rubbing the medication on the area to break off the weaker hairs at the margin of the lesion causing the lesion to appear to get bigger. Neither of these situations truly represents exacerbation of the disease.
Resolution of a localized demodicosis lesion should be at least partially apparent after one month though total resolution can take up to three months.

2: GENERALIZED
Classically with generalized demodicosis, the entire dog is affected with patchy fur, skin infections, bald, scaly skin. Sometimes large patches of affected skin are present, sometimes multiple "polka dots" of lesions cover the dog, and sometimes the entire body is involved. The secondary bacterial infections make this a very itchy and often smelly skin disease. The approach to generalized demodicosis typically depends on the age at which the dog developed the disease.

ADULT ONSET-- Most demodicosis occurs in young dogs, under age one and a half. An older dog should not get demodicosis unless he or she has an underlying problem with the immune system. In such cases, demodicosis is considered a indication to seek a more serious hidden condition such as cancer, liver or kidney disease, or an immune-suppressive hormone imbalance. A more extensive medical work-up will be required.

JUVENILE ONSET -- Young dogs have inherently immature immune systems and are thus susceptible to the development of demodicosis without any sinister underlying diseases. As they grow up and their immune systems mature, they tend to naturally gain control of their mite infestation; in fact, 30-50% of dogs under age 1 year recover spontaneously from generalized demodicosis without any form of treatment. Usually treatment is recommended, though, to facilitate recovery.

3: DEMODECTIC PODODERMATITIS
This condition represents demodectic mange confined to the paws. Bacterial infectious usually accompany this condition. Often as generalized demodicosis is treated, the foot is the last stronghold of the mite. Old English Sheepdogs and Shar peis tend to get severe forms of this condition. The infection can be so deep that biopsy is needed to find the mites and make the diagnosis. It is one of the most resistant forms of demodicosis.