Dog Mange - Walking Dandruff (Cheyletiellosis)
Cheyletiellosis (also called cheyletiella mange) is a highly contagious, nonseasonal parasitic skin disease of dogs, rabbits and cats. It is caused by surface-dwelling Cheyletiella spp. mites. The mites that infest dogs usually are of the species Cheyletiella yasguri. Rabbits are most commonly infested with Cheletiella parasitovorax, and cats are the host species for Cheyletiella blakei. The layman's term for cheyletiellosis is "walking dandruff." This nick-name derives from the fact that these pale to reddish-colored parasites are fairly large, as far as mites go. In fact, they often are large enough that they can be seen scurrying along the dog's skin, or on or just under its hair coat. When moving, Cheyletiella mites indeed do resemble "walking" flakes of dandruff.
Causes of Walking Dandruff
Walking dandruff is the common name for a skin condition caused by infestation of a dog's skin by tiny Cheyletiella mites. These mites burrow through the outer layers of the dog's skin, causing irritation and mild to severe itchiness (pruritis) as a result of mechanical irritation. They produce irritating by-products as a result of dining on the dog's skin and can also secrete substances that cause an allergic reaction (hypersensitivity) in the affected animal. Dogs, cats and rabbits usually become infested with different species of Cheyletiella mites. These mites are highly contagious between members of the same host species. However, dogs, cats and rabbits can become transiently infested with the Cheyletiella mites that normally populate other hosts. This happens through direct contact between an animal carrying the mites and a member of a different susceptible species (dogs, cats, rabbits or even people). For example, a human can become infested by Cheyletiella yasguri mites as a result of petting an infested dog, which is the normal host for that particular species of mite.
Prevention of Walking Dandruff
Since the mites that cause walking dandruff are highly contagious between dogs, the best way to prevent infestation is to avoid direct contact between infested and non-infested animals.
Walking dandruff can affect dogs of any age, breed or gender. This is considered to be a zoonotic condition, which means that Cheyletiella mites can be transmitted from affected dogs to people. When humans develop cheyletiellosis, they usually have an extremely intense itchy reaction and develop small raised, itchy red bumps on their skin that are known as "erythematous papules." These raised red bumps tend to be most prevalent on the person's arms, trunk, abdomen and buttocks. The effects of these parasites on people will resolve once the dog and its living environment are successfully treated.
Cocker Spaniels, Poodles and long-haired cats can be asymptomatic carriers of Cheyletiella mites, which means that they can be infested with the mites without showing any outward signs of itchiness or skin scaling. Asymptomatic or inapparent carriers can become the source of contagion to all other dogs, and to cats, rabbits and people, with whom they come into direct physical contact. Walking dandruff is becoming less commonly seen these days because of the increasingly consistent use of flea-control pesticides, which usually also kill the Cheyletiella mites.
How Walking Dandruff ("Cheyletiellosis") Affects Dogs
Dogs infested with Cheyletiella yasguri mites typically develop a mild to moderate inflammatory skin condition (dermatitis) that is characterized by skin scaling and flaking. The condition may be accompanied by varying degrees of itchiness (pruritis). Some dogs do not seem particularly bothered by the Cheyletiella mites, while others scratch, bite and rub furiously at affected areas.
Symptoms of Walking Dandruff ("Cheyletiellosis")
Symptoms of infestation with Cheyletiella mites usually become evident within about 2 to 6 weeks after a dog has been exposed to a carrier animal. Cheyletiella mites are referred to as "walking dandruff," because they often are large enough to be visible to the naked eye. Owners of dogs with walking dandruff may observe one or more of the following signs:
Scaling and flaking of the skin (non-seasonal; mild to severe; most common along the dog's back and sides – called "dorsal orientation"; flaky, plaque-like scales that resemble dandruff; scaling is the most characteristic clinical sign of walking dandruff)
Skin redness (erythema; variable)
Red bumpy rash, usually along the top of the back
External parasites crawling on a dog's skin and hair, usually greatest in number along the dog's back and sides; 8 legs; pale in color; move slowly)
Scratching, biting, rubbing at affected areas of skin due to variable degrees of itchiness/pruritis (non-seasonal; usually mild but can be intense, depending upon the particular animal's sensitivity to the mites; usually most common along the dog's back and sides)
Dogs at Increased Risk
Dogs that live primarily outdoors, and those that are allowed to roam freely and come into direct contact with other outdoor dogs, have an increased chance of developing walking dandruff. Dogs that have recently been to a boarding kennel, groomer or veterinary clinic, as well as those that have lived in an animal shelter, pet shop or rescue facility, are also predisposed to becoming infected with these mites. Young dogs are slightly predisposed to developing walking dandruff, although it can affect animals of any age. Dogs with weakened or compromised immune system function, and those with debilitating systemic diseases, usually are more severely affected by mite infestation than are healthy animals.
How Walking Dandruff is Diagnosed
Young dogs with heavy "dandruff" over their necks and backs – especially if the flakes of dandruff move – should be suspected of being infested with Cheyletiella mites. They may or may not have any symptoms of itchiness.
The attending veterinarian may recommend a urinalysis and routine blood work (a complete blood count and serum biochemistry profile) to rule out metabolic causes of skin scaling. In many cases, walking dandruff can be diagnosed by physical examination and observation of the mites crawling along the top of the dog's back. A simple "touch tape" technique is frequently used to take a sample of the flaky skin debris. This involves taking a piece of acetate tape and pressing it to the skin and hair where the mites are evident. The plaque-like scales will stick to the tape and can then be examined under a microscope, without staining, for very effective confirmation of their cause. A flea comb is another highly efficient way to obtain samples. Deep skin scrapings and fecal flotation can also be used to collect samples, although these techniques are rarely necessary. Cheyletiella mites are fairly large and frequently can be seen with the naked eye. However, it is more reliable to inspect them using a standard hand-held magnifying lens or a microscope. In those cases where the mites cannot easily be identified, the veterinarian may recommend treating the dog with an insecticide and evaluating its response to treatment. Sometimes, walking dandruff in dogs is not even suspected, much less identified, until lesions (sores) and intense itchiness develop in people living in the same household who have become infested with the Cheyletiella mites.
The main symptoms of walking dandruff – itchiness, scratching and skin scaling - can mimic those of other, more common diseases, such as flea bite dermatitis, food allergies, seborrhea and sarcoptic mange.
The standard treatment protocol for dogs with walking dandruff is weekly bathing to remove the scales, followed by weekly topical treatments with insecticidal rinses for a period of at least 6 to 8 weeks. Two-percent lime-sulfur rinses (LymDyp), and pyrethrin shampoos, are commonly used and reportedly are safe for puppies and dogs, as well as for kittens, cats and rabbits. Other reported treatments for dogs with walking dandruff are Amitraz (Mitaban) dips, subcutaneous injections of ivermectin and/or topical application of Selamectin (Revolution). The attending veterinarian can instruct the owner as to the proper timing and amount of these substances to use. Owners of herding breeds – especially Collies, Shetland Sheepdogs, Old English Sheepdogs, Australian Shepherds, White German Shepherd Dogs and mixes that include one or more of those breeds – should not use ivermectin, as those breeds can be highly sensitive to that medication and suffer a number of severe adverse reactions.
Because walking dandruff is so highly contagious among members of the host species, and even to other species, all pets in the household that have had any contact with the affected dog must be treated. Dogs, cats and rabbits are the primary host species for Cheyletiella mites. The animal's bedding, grooming tools and living environment must be thoroughly cleaned and treated, because these parasites can live for up to 3 weeks or more off of a host animal. Adult female mites are especially prone to survive for a long time in the environment. In many cases, it may be best to dispose of and then replace the dog's bedding, brushes and combs. The environment can be thoroughly cleaned with standard household disinfectants and then treated with parasiticidal foggers, sprays, powders or other products. Products that are intended to kill fleas usually are also quite effective against Cheyletiella mites. Corticosteroids may be recommended in some cases as an adjunct to parasiticidal therapy. If the dog develops a secondary bacterial skin infection (pyoderma) as a result of the mite infestation, a multi-week course of oral antibiotics may also be appropriate.
Depending upon the nature and severity of the dog's condition, treatment for walking dandruff may have to be continued for up to 6 weeks or more before the symptoms resolve. The prognosis for affected dogs is good to excellent if the dog and the environment are treated with the appropriate products for the full recommended period of time. Of course, if Cheyletiella mites remain in the carpet, bedding or other contaminated areas, or if the dog again comes into contact with a carrier animal, the infestation will recur. Being infected with Cheyletiella mites once does not provide any immunity or protection against subsequent infestations.