Cheyletiellosis: Night of the Walking Dandruff

Sorry to mislead you into thinking this blog was going to be about the ever popular zombie creature. It's actually about a different kind of monster, a microscopic mite commonly referred to as "walking dandruff" that likes to prey on bunnies. What better time to talk about mite monsters than Easter? What if the cute little twitch in Peter Cottontail's nose is because of an itch?

Meet "Lucky," a young rabbit presented to our veterinary clinic during the winter of 2014 because of a recently noticed skin condition. Lucky was missing large clumps of hair between his shoulder blades, and the area was covered in huge flakes of white dandruff. His physical examination was rather unremarkable besides his obvious skin disease. He did not even act that itchy, but his skin was quite red everywhere and the hair fell out easily anywhere you parted it.

The other rabbit in the home, kept separately, showed no symptoms of skin disease. The bunnies had been adopted over a year ago and had spent some time penned outside during the warmer months of 2013, but had no interaction with each other much less other animals.

Examination of the affected rabbit revealed a large amount
of dandruff, hair loss and red, irritated skin.

I suspected the "walking dandruff" mite even though no movement was seen in the flakes of dead skin. The official name for this parasitic insect is Cheyletiella and there are numerous species which can plague various mammals from rabbits to dogs to cats. Cheyletiella ("kai-la-tee-ell-a") are highly contagious and can even bite people, but they can't live on us for long. The mites tend to live on the animal's skin within the keratin level; they less commonly invade the nasal passages. The mites are fairly large as mites go, and their scurrying among the excess amounts of dead skin produced in response to irritation resulted in the nickname "walking dandruff."


Animals acquire Cheyletiellosis by direct contact with an afflicted animal in most cases. However, the mites and their eggs can also survive for a short period (days to weeks) within bedding and the environment, so transmission may occur via indirect contact as well. Some animals carry around Cheyletiella mites but don't show symptoms at all! 

At the center of the field are two Cheyletiella mites as well
as a large mite egg.

Definitive diagnosis of Cheyletiellosis in Lucky was swift and satisfying. I collected some dandruff from his back on the sticky side of transparent tape and applied the entire thing to a glass slide. At relatively low magnification under the microscope, I saw numerous mites and mite eggs amid hair shafts and epithelial skin cells.

In some cases, mite bodies and eggs may be seen during microscopic evaluation of a stool sample instead. This is a good way to diagnose Cheyletiellosis in cats. Because they are such fastidious self-groomers, infected cats often ingest the excess dandruff as well as the mites making diagnosis from physical examination alone more difficult.

Fortunately, treatment of "walking dandruff" is much easier than eliminating an apocalypse of the walking dead. Various treatments are available to kill Cheyletiella mites. Because rabbits are weirdly sensitive to certain topical insecticides--for instance, over-the-counter products containing fipronil, well-tolerated in dogs and cats for the treatment and prevention of fleas, are devastatingly toxic to rabbits--we selected topical prescription-only selamectin which has been used safely and effectively in rabbits for mites of various kinds.

Dr. Kim Everson applies a dose of medicine to Lucky to treat
his bad case of Cheyletiella mites.

In addition to thoroughly cleaning the hutches and surrounding environment as well as replacing the bedding and feed hay, we decided to treat the asymptomatic rabbit as well. Both bunnies will receive a small amount of medicine on the skin between the shoulder blades once a month for several months in a row. Any mite bites on the humans in the household are expected to resolve once the bunnies have completed treatment.

Shortly after the first dose of medicine, Lucky was reportedly showing signs of improvement in his skin. By now, he should be feeling fine -- just in time for delivering the family's Easter baskets!

Fuzzy the Saber Tooth Rabbit

Severely overgrown rabbit incisors. 

Bunnies are supposed to have "buck teeth" but their teeth are not supposed to resemble fangs (unless we're talking about literary legend Bunnicula). Malocclusion, or misalignment of teeth, is not just an unfortunate cosmetic problem. It can be an uncomfortable and life threatening disease!

Rabbits can have malocclusion or bite problems in either their incisors or cheek teeth. Incisors are the central paired top and bottom teeth. Cheek teeth are the premolars and molars beside the cheek which are used for grinding food. The incisors and cheek teeth of rabbits grow, or erupt, continuously. Normally, this growth is held in check by dental abrasion from chewing a diet high in fiber. Malocclusion issues cause overgrown teeth or razor sharp points on the cheek teeth which lead to difficulty eating, poor digestion, weight loss, drooling and painful or infected sores in the mouth.

Regular trimming of this bunny's incisors is necessary. 

At a little over 18 months of age, Fuzzy's bottom incisors had grown to nearly an inch long. Soiled, matted fur was caught in the bottom teeth. His upper incisors, not readily visible, were also too long and were starting to grow into the roof of his mouth! Fuzzy's owner had provided numerous chew toys in the hopes his teeth would naturally wear down. However, Fuzzy's severe underbite prevents him from bringing his upper and lower incisors together when he chews so the teeth do not wear down properly. Luckily, a thorough history and physical exam revealed no other significant problems. Fuzzy still had a good appetite, was passing normal stool, was a healthy weight and had a glossy hair coat. Even better, Fuzzy's malocclusion problems were limited to his incisors and his cheek teeth were normal! We were able to trim Fuzzy's upper and lower incisors during the appointment. Fuzzy will require regular tooth trimmings in the future to prevent such extreme overgrowth and secondary problems.

Rabbits are an increasingly popular pet. Proper husbandry (diet, housing, and preventive care) is essential for keeping pet bunnies happy and healthy. The Rabbit House Society offers useful information on the care and enjoyment of pet bunnies. Regular preventive care by your veterinarian is also recommended. Immediate veterinary examination is essential for pet rabbits that have not eaten in 24 hours, have diarrhea or are not defecating at all. Injury to the spine or legs, infections and parasites are also important problems. Use caution and consult your veterinarian before using any over-the-counter medications or parasite treatments because certain common antibiotics and flea treatments, for example, can be deadly to rabbits.