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!

Inspiration

Tonight I was asked by my neighbor to remove a kernel of corn from her son's ear canal.

Swallowing chuckles, flanked by his desperate mother aiming a light at the barely protruding foreign body and my incredulous son (his best friend), I try first to suction the kernel out with a baby nasal aspirator. Failing with this approach, I grab a pair of finely pointed forceps from my veterinary cold sterilization tray.

The boy whimpers when he sees the instrument, although it is no more sinister than a pair of tweezers. 

"You must hold still," I warn. "If this doesn't work, you're off to the hospital."

With a steady hand and held breath, I reach into the opening of the ear canal and grasp at the kernel. The offending golden seed glides from the boy's ear. It feels as though I just successfully grabbed the "funny bone" from the Operation man without setting off a buzzer.

Amid cheers and high fives, we part ways for the evening. My arm around my son's shoulders, I have a weird nostalgia feeling as we walk into our house. I'm rather proud of my performance and wonder if my son is similarly impressed. And I'm thinking of my own mom being heroic under extraordinary circumstances in a memory from so long ago it feels more like a dream than reality. In college I commemorated the experience with the following poem later published in UW Eau Claire's 1998 NOTA. In honor of moms everywhere rocking at improvisation in times of crisis (and with its slightly spooky Halloween theme), I present:

Mother

The skinny
scream of the bunny
pierces the adults
to their kitchen
perches—
all except for Mother
who flies to her bare feet
and in a voice I've never
heard—vibrant and
strong—summons
Towels!
Thread!
Needle!
Suddenly the objects
appear, submitted
by leaf-trembling
children sooted with
alfalfa dust and wearing gnome-like
wigs of spiky yellow straw.

While the bunny
cries on the table,
she grasps
the torn flap of hide,
rinses dust and leaves
from the bloody meat beneath—
silent now,
surrounded by silence,
except for the spiraling
shriek of the bunny.
She holds him between
her legs, pressing him still
with solid thighs, as she
calmly weaves black
thread through the eye of the needle.

As easily as she glides
our summer green
cucumbers—
warty legless frogs—
into the boiling cauldron
to pickle,
Mother eases the needle
through one slice of soft
hide into the other,
pulling the torn pieces
taut into the whipstitch.

She needs no
finger-pointing from
the stunned children
to divine the truth.
The evil eye she
levels at the smallest two
boys—the ones whose tug
of war broke the animal—

is not a curse, not hatred
but fear and shock and
sadness.

Still wordless
she knots the thread
as peacefully as tying
off a newly darned
sock, rests the quieting
bunny in a shoe box
and sighs,
breaking the spell.

That bunny ain't dropping Easter eggs

Years ago, pregnant with my first child and having no veterinary training yet, I acquired a young Nubian goat kid with diarrhea. Fecal testing revealed a protozoan parasite referred to generically as coccidia. A cautious expectant mother, I asked my physician if exposure to goat coccidia was harmful to my unborn baby. When he reported back that goat coccidia (Eimeria spp.) are "host specific" -- meaning goat Eimeria are contagious only to other goats -- I was very relieved.


Flash forward a decade and I find myself, now an animal doctor, doling out this same information to dog owners on a regular basis. Finding microscopic coccidia eggs on an annual fecal float test is not uncommon. Dogs may pass Isospora or Eimeria eggs in their stool, but as with goats these coccidia parasites are "host specific." As I explain this to horrified pet owners, they are relieved to hear it is not contagious to them or their children.

A small sampling of the oodles of eggs
-- coccidia, not Easter -- being passed by two
sick bunnies I saw this month. 

Identifying the presence of coccidia is easy. Now here's where it gets tricky. Remember that coccidia are "host specific." If a dog tests positive for an Isospora-type coccidia it may require treatment because Isospora is a dog coccidia. But if an Eimeria-type coccidia is seen, the dog is simply pooping out the coccidia that a rabbit once pooped out. Quickly differentiating between Isospora from Eimeria based on subtle differences in size or ornamentation takes practice and experience. Nevertheless, seeing as nibbling rabbit poop is a pretty common canine past time, chances are pretty good that many dogs are pooping out a non-canine coccidia.*

Many animals host coccidia without any outward signs of illness. In fact, sickness generally occurs only in very young animals during times of stress. As in my goat kid, coccidiosis may cause severe diarrhea. My yellow Labrador developed screaming diarrhea a few days after we brought him home as a puppy thanks not only to Isospora spp. but also to the stress of leaving his litter. Some of my canine patients--puppy or adult--that test positive for coccidia have unexplained scooting or butt licking without abnormal stools. A short course of treatment for coccidia often relieves all these symptoms.

I recently examined two very young bunnies with diarrhea and lack of appetite. These baby bunnies had been turning up their twitching little noses at hay and pellets for several days, eating nothing but carrots (a treat, not a balanced meal). The day I examined them they had been passing liquid orange stool for several hours. Not having had an occasion to test a pet rabbit's stool before, I was unsure of what I would find. Imagine my surprise when I focused my microscope on the fecal float slide to find hundreds of oval eggs. Coccidia! Eimeria-type no doubt. Treatment with anti-coccidia medication--a teeny tiny portion of the average dog dose--was started immediately, and the owner decided to provide additional nursing care at home.

What fascinates me about this case is not so much identifying rabbit coccidia -- as I explained, we veterinarians see it all the time as an incidental finding on canine fecal floats. It's just that I had never seen so much of it in one place. And never had I paused to think about what the rabbit coccidia might do to the rabbit! The story of these two very sick baby bunnies overwhelmed by coccidia has given this parasite a face and personal meaning to me.


* Cats can be infected with or shed coccidia in their stool as well including various species of Isospora or Eimeria which are not contagious to people. 

Cuterebra are not cute (and maggots are just plain gross)

Parasites create a buzz of excitement in a veterinary clinic. Creepy, crawly, stinky? Bring it on!

This week was especially interesting with the appearance of two different species of parasitic larvae arriving inside the skin of two of my mammal patients. The technical term for parasitic fly larvae is "myiasis."

Rabbit afflicted with Cuterebra larva

First, a father called worried that his daughter's pet bunny had been shot with a B-B gun while it was in its outside enclosure because it had a hole on either side of its neck. When the bunny arrived she was bright and alert. Although she had two large wounds on her neck that were leaking fluid and pus, I learned she was not acting sick at home. As I prodded one of Flopsy's wounds a little maggot head peeked out at me! "Cuterebra!" I exclaimed happily.

While disgusting, cuterebriasis is a common and treatable condition in rabbits. Sometimes these larvae show up in the skin of kittens, cats and dogs as well. In the spring and early summer the female Cuterebra fly lays her eggs on blades of grass. When a rabbit or other mammal brushes against the infected grass, the egg or a recently hatched maggot attaches to its fur and then eventually burrows under the skin where it sets up shop. Occasionally these maggots migrate to the wrong place (like the lungs or brain) and cause all sorts of problems, but usually they mature into grubs inside their "warble" under the skin. Eventually they drop off the animal back into the soil where they finish developing. The B-B sized holes seen on Flopsy are the grubs' tell-tale breathing holes.

Removing Cuterebra larva from its warble under the skin

I very carefully removed a pair of fat Cuterebra grubs from Flopsy's neck, cleaned the wounds and started her on an antibiotic for the secondary bacterial infection in her skin. While removing Cuterebra larvae, care must be taken not to break or rupture the grub inside the skin because the pieces will cause festering wounds.*

I know it may be a matter of personal preference, but I find that while Cuterebra are not cute, they are definitely not as disgusting as regular old maggots. Our second myiasis patient, Trina, was an obese outdoor kitty who came in crawling with maggots. Trina had a terrible skin infection around her vulva (she couldn't clean herself because she was so obese) and a ruptured anal gland abscess. Flies had been attracted to her stinky, moist, dying flesh and had laid eggs there. We pulled dozens of wriggling white maggots from Trina's skin, inside her vulva and surrounding fur. (Yes, it was gross even for us veteran parasite handlers.) Then we shaved off the nasty matted fur on her back end, cleaned her wounds and administered pain medication and antibiotics. By the time we finished Trina looked, smelled and felt a million times better. Once we get her through this rough patch, Trina's family and I will be working together to get the extra Lbs off her.

*One theory behind the medical and veterinary symbols of a "snake" wrapped around a staff may stem from a skin parasite in people called Guinea Worm (dracunculus medinensis).  A traditional method of treatment is to wrap the end of worm around a small stick, gradually and carefully twisting the stick until the worm is completely extracted from the person's skin. Breaking the worm inside the skin can create a life-threatening bacterial infection such as tetanus.

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.