Cheyletiellosis in Dogs (Walking Dandruff Mite)

Cheyletiellosis is an itchy, scaling skin disease of dogs caused by infestation with Cheyletiella mites. It is often called "walking dandruff" because when you examine an infested dog, you may see that the "dandruff" is moving. The movement is actually caused by the mites moving around under the scales. Although the mites inhabit the entire body, the scaling and itching often seem worse over the back.

Cheyletiellosis is a contagious and a zoonotic disease, which means that it can be spread to and from other dogs, cats or humans. Dogs can acquire the infection from other pets or humans. The mite is transmitted by close contact with infested animals. Since the mite can live for a few days off the host, it is also possible to become infected through environmental contamination. Eggs are also shed into the environment, which is believed to also be an important cause of re-infestation. 

This disease is very contagious making it more prevalent in shelters, humane societies, boarding facilities and grooming establishments where there are lots of pets. Poor sanitation, poor nutrition and overcrowding can lead to infestation. Thus, it is likely for puppies from puppy mills to show up in pet stores with this problem. 

Puppies seem to be more susceptible than older animals, but infestation of adults is sometimes seen. Cocker spaniels appear to be predisposed. 

The discomfort of itching and the lesions the animal can cause to himself by scratching is directly related to the impact of this disease on the dog. 

What to Watch For

Flaky, scaly hair coat (especially over the back)

Itchiness (in some pets)

Redness of skin (in some pets)

Diagnosis

A medical history may reveal a scaly, itchy skin problem on one or more of the animals in the home, often after a recent addition of a new pet. These mites can temporarily infest people, so you may experience an itchy rash on arms, belly, back and chest.

Your veterinarian will do a physical exam, which will probably reveal the characteristic scaly skin along the dog's back. However, not all animals show this distribution of lesions. These mites are large compared to other mites and in cases of heavy infestation, you can see them on the skin with a magnifying glass.

Other diagnostic tests may include:

Flea comb. Combing with a flea comb is probably the most reliable method of diagnosis. The dog should be thoroughly combed all over the body and the scale that is collected on the comb should be viewed under a microscope. The scale may also be placed on a dark background and observed. These mites appear as white specks that move, hence the name "walking dandruff" mites.

Skin scrapings. Microscopic evaluation of skin is less accurate than flea combing in light infestation because only a small area of skin is evaluated. Skin scrapings are often done to rule out other itchy skin diseases like scabies, and the mite may be picked up in the process.

Acetate tape. Impressions of the skin with clear acetate tape can pick up mites, which can then be seen when the tape is placed on a drop of mineral oil on a slide and viewed under a microscope. This method also has the disadvantage of sampling only a small area.

In cases where mites cannot be found, but a parasite is suspected, your veterinarian may elect to treat for the disease and look for a response to the treatment.

Treatment

Although commonly used flea sprays, shampoos and powders may give temporary relief, more aggressive treatment is needed for long term success of walking dandruff mites. Because this disease is contagious, all pets in the home should be treated.

Treatment includes:

Ivermectin is an effective treatment for cheyletiellosis. It may be given by subcutaneous injection or orally. However, ivermectin is toxic (For more information go to Ivermectin Toxicity) in herding breeds such as collies, Shetland sheepdogs and other breeds. This drug is usually used every 1 to 2 weeks for at least 4 weeks.

Selamectin (Revolution), Imidacloprid (Advantage) and Fipronil (Frontline) , are topical drugs that are applied to the skin of dogs between the shoulder blades. These drugs show promise in treating cheyletiellosis. They are often applied monthly for at least two months.

Lime sulfur dips are effective, although clipping of the hair coat may be necessary in medium and longhaired breeds to get the best results. Dips may need to be done weekly for 6 to 8 weeks.

Sprays containing pyrethrin can be used in weekly applications for 3 to 4 weeks.

Amitraz dips are also effective and used every week for 3 to 4 weeks.

Whatever treatment is selected, it is important to treat all animals in the household.

Prognosis

The Prognosis is good with effective therapy and treatment of all pets in the home.

Home Care and Prevention

Treatment of the home environment may be necessary to prevent re-infestation. Wash all bedding and discard brushes and combs. Vacuum carpets and upholstery thoroughly and repeatedly and spray the house with a flea premise spray.

Although it is difficult to prevent infestation by the walking dandruff mite, you can take some steps to lower exposure. You should avoid the dog while he is infested since the mites are highly contagious.

Be sure to have any new animals evaluated by a veterinarian before admitting them to your home. Cheyletiellosis can be contagious to people so anyone handling the pet should thoroughly wash their hands and use appropriate caution.