A little mite causes a lot of trouble for Lacey.
Demodectic Mange – Lacey’s Mum was the culprit.
(Sometimes called red mange or demodicosis)
The Culprit – Demodex Canis
Demodectic mange, also called demodicosis, is caused by a microscopic mite of the Demodex genus. Three species of Demodex mites have been identified in dogs: Demodex canis, Demodex gotoi, 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 through cuddling during the first few days of life. Most dogs live in harmony with their mites, never suffering any consequences from being parasitized. However, if 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.
Is Demodicosis Contagious?
Demodectic mange (unlike sarcoptic mange) is not considered a contagious disease and isolation of affected dogs is generally not considered necessary. That said, there are some circumstances under which the mites could spread from one dog to another.
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 no longer accept new mites on its body. It should not be contagious from one pet to another and is not contagious to people and cats.
Mites live inside hair follicles — a difficult place for miticides (chemicals that kill mites) to reach.
Mites are normal residents of dog skin; it is only in some individual dogs that mites cause problems.
Demodicosis has Three Forms
Form #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.
Some guidelines used to distinguish localized demodicosis include:
- 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 four spots total on the dog.
Resolution of a localized demodicosis lesion should be at least partially apparent after one month although total resolution can take up to three months. 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 one year of age recover spontaneously from generalized demodicosis without any form of treatment. Usually treatment is recommended, though, to facilitate recovery.
Approximately 10% of localized demodicosis cases will progress to generalized demodicosis. Enlarged lymph nodes are a bad sign, often foretelling generalized mange.
Form #2: Generalized
Classically, with generalized demodicosis the entire dog is affected with patchy fur, skin infections, bald, scaly skin.
Sometimes there are large patches of affected skin, and sometimes multiple “polka dots” of lesions cover the dog, and sometimes the entire body is involved. The secondary bacterial infections make this an itchy and often smelly skin disease. The approach to generalized demodicosis typically depends on the age at which the dog developed the disease.
Form #3: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 an 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.
IT IS IMPORTANT THAT DOGS WITH A HISTORY OF GENERALIZED DEMODECTIC MANGE NOT BE BRED AS THERE IS A HEREDITARY COMPONENT
Treatment: Stress and Generalized Demodectic Mange
The treatment of demodicosis only in part relies on medications; some basic steps can be taken with regard to pet care to maximize the chance of success. Physiological stress is an important factor determining the degree of severity of demodectic mange and the following steps should be taken to reduce stress:
- Females should be spayed as soon as the disease is controlled. Coming into heat, hormone fluxes, and pregnancy are very stressful. Also, predisposition to demodicosis is hereditary and should not be passed on.
- The dog should be fed a reputable brand of dog food so as to avoid any nutritionally related problems.
- Keep the pet parasite-free. Worms are irritants that the pet need not deal with and fleas may exacerbate the itchiness and skin infection.
- Keep up the pet’s vaccinations.
- The mites cause suppression of the immune system so the pet needs every advantage to stay healthy.
- Skin infections are usually associated with these cases and antibiotics will likely be necessary. It is important that cortisone type medications such as prednisone NOT be used in these cases as they will tip the immune balance in favor of the mite.
Treatment: Medications
Current Treatment of Choice — Ivermectin
Ivermectin is a broad spectrum anti-parasite medication with a number of uses though its use in treating demodicosis is not approved by the FDA. When ivermectin was a new drug it was hoped that it could be used against demodectic mange mites as at that time only fairly toxic dips were available and incurable cases were common. After some experimentation it was found that daily or every other day dosing is necessary for effective demodicosis treatment and soon ivermectin was felt unequivocally to be the drug of choice for this condition. Note that the weekly protocols that work for other parasites simply do not work on Demodex mites.
THIS MEDICATION CANNOT BE ASSUMED SAFE FOR USE IN COLLIES, SHETLAND SHEEPDOGS, AUSTRALIAN SHEPHERDS, OLD ENGLISH SHEEPDOGS AND, SOME WOULD SAY, ANY HERDING BREED.
The high doses of ivermectin used in the treatment of demodicosis are not compatible with the commonly used flea product spinosad (Comfortis®). The combination of spinosad and high doses of ivermectin will increase the likelihood of ivermectin neurologic side effects. While flea control is very important during the treatment of demodectic mange, a different product should be used.
Prognosis
The younger the dog, the better the chance of cure is. Most dogs less than one year and a half years of age recovery completely from generalized demodicosis. In many cases of adult-onset demodicosis, the disease is controlled with treatment but cure is not always possible. Some cases can never be controlled.
Treatment, no matter which option is chosen, should be accompanied by skin scrapes every 2 weeks. In this way the effectiveness of treatment is assessed and modifications can be made. After two consecutive scrapes are negative, treatment is discontinued but a final scrape should be performed after one month off therapy. The reason for the final scrape is to be sure the mites are not coming back (which they can do if every single mite on the dog is not eradicated).
Relapse?
When relapse occurs it is often because the dog appeared to be normal and the owner did not return for the appropriate re-scrapings. Relapse is always a possibility with generalized demodicosis as there is no easy way to confirm that every mite has been killed, but most dogs that relapse do so within a 6 to 12 month period from the time they appear to have achieved cure.