Walking dandruff in dogs – symptoms and treatment

Overview

A mite living on the skin surface

The most common Cheyletiella species in dogs is Cheyletiella yasguri. This pale arachnid lives in the surface layer of the skin. It lives on the surface rather than burrowing into the skin. The disease is also called cheyletiellosis, meaning Cheyletiella mite infestation.

An adult mite is about 0.5 millimetres long and may be visible to the naked eye. The name walking dandruff describes how the mites' movement makes skin flakes appear to move. Infestation may cause only slight scaling or a clearly itchy skin rash. Cheyletiella mites occur in dogs and cats around the world.

Causes

Direct contact and the environment

Walking dandruff spreads particularly readily when animals have close contact. Spread between dogs, cats and rabbits is also possible, although each mite species has its usual preferred host. The source may be an animal whose skin looks completely normal. Mites and hairs bearing eggs left in the environment can sustain infestation.

From egg to adult on the dog's skin

The mite feeds by piercing the skin surface and sucking tissue fluid. The female attaches her eggs to hairs with fine strands. Eggs hatch into larvae in about 4 days. The larval stage is followed by nymph stages and finally the adult mite. A larva has 6 legs. After the larval stage, the mite passes through 2 nymph stages. The entire life cycle takes place on the host animal and lasts about 3 weeks. An infestation starting from a single mite is estimated to take 3–5 weeks to develop. This does not mean every dog starts itching after exactly the same interval.

A female mite can survive off the animal for up to 10 days. A survival period of 10–14 days in the environment has also been reported for adult mites. Unlike females, larvae, nymphs and adult males die soon after leaving the host animal. Cool, damp conditions may prolong survival. Environmental cleaning is therefore part of breaking the cycle of infestation.

Risk factors

Puppies and animals in poor condition appear more susceptible to walking dandruff infestation. Reduced immune defences are also associated with more frequent infestations. Large breeding establishments and other settings bringing many animals together increase exposure. Dogs may be exposed in shelters and grooming establishments, for example, where many dogs have contact with one another.

In homes with several pets, contact between different animal species also matters. An adult dog may have no signs even though a puppy living with them is itchy and scaly. There is no clear risk classification based on breed or sex.

Typical symptoms

The typical change is increased scaling over the back and upper body. Signs may initially be so slight that you do not notice them. Possible findings include:

• Dry, bran-like flakes, particularly in the coat over the back.
• Greasy-looking scaling around the head and back.
• More frequent scratching and itching of variable severity.
• Skin redness and localised crusted lesions.
• Small, pale moving specks in the coat or among the flakes.
• Thinning hair as the signs spread more widely.

Some dogs itch intensely, while others do not itch at all. The scaly skin may otherwise remain fairly normal in appearance. Even a small number of mites can be associated with very severe itching. A hypersensitivity reaction to the mites may explain this. Severe lesions can resemble sarcoptic mange. Itchy skin lesions in a person may also be the first clue to a pet's infestation.

Complications and consequences

A continuing cycle of infestation

An untreated carrier can pass mites back to a pet that has already been treated. An uncleaned bed can also provide a source of renewed exposure. Disappearance of signs does not always mean that all mites have left the animal. The outlook for recovery from appropriately treated walking dandruff infestation is generally excellent.

Skin symptoms in people

Walking dandruff mites can cause itching and small raised spots in people who have contact with an animal. Symptoms may occur particularly on the arms and trunk. Humans are incidental hosts, and infestation does not usually become permanent. Sustained reproduction does not occur on humans. There is no evidence of spread from person to person. Human skin symptoms may disappear within about 3 weeks after the pet and environment have been treated.

Diagnosis at the vet

History and contacts

Diagnosis is based on the dog's history, skin lesions and identification of mites or their eggs. Your vet also asks whether other animals or people in the home have similar skin symptoms. Walking dandruff is considered in an itchy, scaly dog even when the initial suspicion is an allergy.

Samples from the coat and skin surface

A flea comb is used to collect flakes and surface debris from the coat over the back for microscopic examination. During combing, the comb must reach the skin surface so that surface material enters the sample. A sample can also be collected by pressing transparent tape against scaly skin. Hair over a small area may be clipped for sampling. Hair samples can be examined for mite eggs attached to the hairs. The eggs are about 240 micrometres long. Cheyletiella eggs resemble louse eggs but are smaller and more loosely attached to the hair. A mite egg lacks the characteristic cap of a louse egg. An adult walking dandruff mite has 8 long legs. Large, curved hooks on the mouthparts help identify the adult mite.

A superficial skin scraping is one possible test, but sampling methods may need to be combined. A routine scraping may be negative because the parasite lives on the skin surface. Collected material can be examined in mineral oil, which prevents live mites escaping from the sample. A clinic may also use a vacuum fitted with a filter to sample a large area of the coat. Eggs swallowed during licking can sometimes be found on faecal examination.

A negative sample and other possible causes

Mites can be difficult to find, especially in an animal carrying few parasites or bathed frequently. A negative sample therefore does not rule out infestation if the signs and exposure fit. Your vet may then assess the response to a treatment trial. A reduction in itching and skin lesions within 1–3 weeks of starting antiparasitic treatment supports the suspicion.

Other causes of scaling include other external parasites, nutritional problems and disorders of skin keratinisation. Intestinal parasites are also considered when investigating an itchy dog with marked scaling. Walking dandruff mites can additionally cause a false positive dust mite skin test through cross-reaction. Parasite infestation is therefore investigated before planning allergen immunotherapy.

Treatment

An antiparasitic medicine selected by your vet

Several topical and systemic antiparasitic medicines, which act throughout the body, are effective against walking dandruff mites. Possible active ingredients include selamectin, moxidectin and fipronil. Your vet prescribes treatment and selects a medicine according to the animal species being treated. Treatment of walking dandruff may require a medicine to be used outside its officially authorised indication. An ordinary flea spray or powder may not be effective enough to eliminate walking dandruff mites.

All exposed animals are considered

Dogs, cats and rabbits in the same household are treated at the same time. Contact animals without signs are included because they can sustain infestation. Close animal contacts outside the home are also considered. A medicine suitable for a dog may not suit a cat: permethrin and amitraz are contraindicated in cats.

Environmental cleaning and assessment of treatment success

Beds are washed and the living environment vacuumed to remove mites. Other surfaces touched by the animal are also cleaned thoroughly. Unnecessary or difficult-to-clean items carrying infestation may be taken out of use. Eradicating infestation can be particularly difficult in large groups of animals.

The end of treatment depends on eliminating the parasites, rather than simply a reduction in visible flakes. Follow-up visits may include another examination of the coat and skin surface for mites. If signs return, both untreated carriers and possible environmental sources are investigated.

Prevention

Spread of walking dandruff is controlled by identifying infestation and treating affected and exposed animals. Scaling and itching in a new puppy should be investigated, especially if the puppy came from a large group of animals. Assuming an adult dog without signs is completely free of infestation on appearance alone can allow exposure to continue.

External parasite protection planned by your vet may also help prevent walking dandruff infestation. Washable bedding and vacuuming help remove possible sources of reinfestation. Sleeping with an infested pet increases close exposure for people. Children's exposure to a potentially contaminated environment is reduced. Hand hygiene forms part of reducing infection risks associated with animals' external parasites.

Important for dog owners

Record when scaling started, where it occurs and how much your dog scratches. Photograph the same skin areas to monitor changes. Tell your vet about new pets, boarding or care arrangements, grooming, and skin symptoms in other animals and people. This information helps investigate infestation.

Make a list of all dogs, cats and rabbits that have had close contact. Arrange their treatment according to your vet's instructions. Treating only the puppy with signs is insufficient if other contact animals carry mites. Also identify beds and other frequently used resting places for cleaning.

Show itchy skin lesions in a person to a doctor and mention the pet's confirmed or suspected walking dandruff infestation. Do not use an animal's prescribed antiparasitic medicine on a person. During treatment, monitor your dog's skin and other pets' signs, and attend the agreed follow-up visits. Settling of itching does not always mean your dog is already completely free of mites.

Frequently asked questions

Can you see walking dandruff mites with the naked eye?

A mite about 0.5 millimetres long may appear as a small, pale moving speck among the flakes. Identification is confirmed by examining a mite or eggs under a microscope. Mites may still be difficult to find, particularly if there are few of them or the dog has been bathed frequently.

Can a dog's walking dandruff affect people?

Walking dandruff mites can cause itchy raised spots in people after animal contact. Humans are incidental hosts, so infestation does not usually become permanent. Treating pets and the environment stops renewed exposure. A doctor assesses human skin symptoms and should also be told about the pet's confirmed or suspected infestation.

Does a dog without signs also need treatment?

Yes. Pets that have been in contact with an infested animal are treated even if their skin looks normal. An animal without signs can carry mites and pass them to other pets. Your vet chooses suitable treatment for each animal species.

Can you rely on a negative skin scraping?

One negative sample does not rule out walking dandruff if the signs and exposure history fit infestation. Mites can also be sought by combing, tape sampling and hair sampling. Your vet may additionally use a reduction in itching and skin lesions during a treatment trial to support the diagnosis.

Why does walking dandruff return after treatment?

Reinfestation can come from an untreated contact animal or an uncleaned bed. Visible signs can also disappear before all the mites are gone. Treatment success is therefore assessed through follow-up visits planned by your vet and, where necessary, repeat examinations of the coat and skin.