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!

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. 

Dirty Jobs: Considerations for Cleaning up Wildlife Latrines

Making the most of the unseasonably mild November weekend, we set to work converting an old ice shanty into a deer stand instead. The shanty had been abandoned to the weeds years before, but aside from a broken window and a rip in one of the tin-sided walls, the little building was in remarkably good shape. As we sifted through random lumber, old magazines and broken glass inside, we encountered a raccoon latrine in one corner.

An attic raccoon latrine

If you've never seen a raccoon toilet before you're lucky. Raccoon poop is surprisingly large and bulky. Once a raccoon has picked a toileting spot, he and other raccoon will make repeated deposits there. If the public raccoon toilet happens to be in your attic, barn or shed, you have a real mess to clean up. However, cleaning up wildlife waste sites is not without risk. The eliminations of many creatures can carry various disease-causing micro-organisms.

Rodent Excrement

In the early 1990s an outbreak of a sometimes fatal respiratory illness in humans occurred in southwestern U.S. Also known as Four Corner's Disease and Sin Nombre virus, the causative agent was determined to be  hantavirus and was linked to exposure to mouse droppings. More recently in late summer 2012, eight cases of hantavirus (including three deaths) were confirmed in an area of Yosemite National Park. Hantavirus can be found in rodent saliva and droppings, so people risk exposure to infection when removing rodent nests. Aside from supportive care, there is no specific treatment for hantavirus. To reduce exposure to potentially infectious rodent droppings, the Centers for Disease Control (CDC) offers the following advice.

• When opening an unused cabin, shed, or other building, open all the doors and windows, leave the building, and allow the space to air out for 30 minutes.
• Return to the building and spray the surfaces, carpet, and other areas with a disinfectant. Leave the building for another 30 minutes.
• Spray mouse nests and droppings with a 10% solution of chlorine bleach or similar disinfectant. Allow it to sit for 30 minutes. Using rubber gloves, place the materials in plastic bags. Seal the bags and throw them in the trash or an incinerator. Dispose of gloves and cleaning materials in the same way.
• Wash all potentially contaminated hard surfaces with a bleach or disinfectant solution. Avoid vacuuming until the area has been thoroughly decontaminated. Then, vacuum the first few times with enough ventilation. Surgical masks may provide some protection.

Pigeon Droppings

Pigeons are an expensive nuisance in urban areas. Their droppings are not only messy, but also are potentially loaded with disease-causing agents. Two types of common soil fungi sometimes grow happily in pigeon poop and can cause serious illness in people when aerosolized. One such fungal disease, histoplasmosis causes fatigue, fever and chest pains in people with high exposure to contaminated droppings. The other, cryptococcosis, can cause lung infections. Both types of fungal disease tend to be worse in immune-compromised people. A third pigeon-poop disease, psittacosis, is caused by bacteria that can be found in the droppings of pigeons as well as some types of pet birds. Inhalation of airborne bacteria may cause flu-like illness and even pneumonia. All three of these infections can be treated with antifungals or antibiotics.

Bat Guano

Bats get a bad enough rap as being a reservoir for the rabies virus. This deadly infection is transmitted via an infected bat's bite not through the bat's waste products. Like pigeon poop, bat guano can contain the fungal organism that causes histoplasmosis. In some parts of the world, the excrement of some bat species has been linked to numerous viruses that affect livestock and people.

Raccoon Latrines

Baylisascaris procyonis, intestinal parasite of raccoon

The raccoon poop piled in the corner of my little shed is not just a foul mess. It almost certainly contains a type of intestinal worm called Baylisascaris procyonis that can infect a variety of animals including dogs and humans if accidentally ingested. Human infections are rare, but can be severe if the parasites invade the eye, organs or the brain. Diagnosis of Baylisascaris infection in pets is made by evaluating a stool sample under the microscope. Special dewormers are needed to treat this type of roundworm in pets and may be used to treat human infections with variable success. Raccoons cause so much damage to property that making your buildings inhospitable to them by securing openings and removing food sources (including pet food) goes a long way to reducing your exposure to their fecal parasites.

The afternoon rain prevented us from following through on the CDC's suggestions for cleaning up a raccoon latrine. But we will be back armed with masks, gloves and shovels. We will probably also have to paint over the raccoon toilet with Kilz primer to seal in odor and make the shack a neat place to hang out. Knowing that we need to take a few simple precautions with our nasty clean-up project will significantly lower our risk of infection.

Ring Around the Ringworm

Ringworm is one of my least favorite parasitic diseases. {Having written that prompts me to ask myself what is my most favorite disease! Ear mites are definitely high on the list of creepy, cool parasites that are fun to treat.}

A cat with ringworm lesions on its face (hairloss)

Anyway, I hate ringworm. It is a common, non-lethal contagious fungus (not a worm at all as the name suggests) that infects the skin, hair and nails. There are many different species of ringworm fungi, or dermatophytes, and they can affect just about any species of mammal imaginable: goat, horse, cow, guinea pig, dog, cat, human. Ringworm is fairly ubiquitous in the environment, hanging around in the soil, animal housing structures, and of course on the skin and fur of the animals it calls home.

In animals, a ringworm infection typically appears as patches of hairloss sometimes with crusty, scaling skin underneath. On people, the fungus usually creates a reddish ring-shaped rash on the skin (hence the name). It is variably itchy. Prognosis for a cure is very good with appropriate treatment.

There are several reasons why I hate ringworm.

1. It is zoonotic. This means infected animals can share the fungus with people. In fact, many times pets are presented to me for inspection because a human family member has classic ringworm symptoms and the pet is the suspected source. It stinks when the cute cuddly new kitten is suddenly a pariah.

2. It is sneaky. Like a Typhoid Mary, a ringworm carrier can quietly infect a legion of other animals and never even appear sick. Therefore, even though it is not a deadly disease, it is a population medicine nightmare. In animal shelters, ringworm is an endemic threat to the health and adoptibility of the animals. A ton of money and time is spent testing, treating and retesting shelter animals, especially cats, for ringworm. In some shelters, cats entering the shelter with known or suspected ringworm might even be euthanized to prevent its spread.

3. There is no one great test. A Wood's lamp can help screen dogs and cats for ringworm because a fair number of cases will fluoresce, or glow. I become quite giddy when a cat or dog ringworm suspect lights up like a city skyline at night under the Wood's lamp. {It's almost as cool as watching ear mites swim through mineral oil under microscope magnification.} Definitive diagnosis of ringworm, however, is made by culturing the organism from the fur. This test can take days to weeks and occasionally fails due to the persnickety nature of certain ringworm types who may refuse to grow well in the lab.

Lime dipping a cat with ringworm

4. There is no one great treatment. A diagnosis of ringworm comes with a laundry list of different topical and oral treatment options. Some are antiquated and dangerous. Some are stinky, messy and flat out obnoxious. Others are terribly expensive. Current veterinary protocols for treating ringworm usually involve a combination of multiple obnoxious lime dip baths and costly oral antifungal medication.

5. A ringworm household can turn into veritable Superfund Site. Ringworm is spread through "hairborne" fungal spores, which easily become airborne on shed fur and dust. Careful, thorough vacuuming and dusting (including heating/cooling ducts if the ducts culture positive) and laundering is necessary to prevent re-infection of the affected animal. A bleach solution can be applied to bleach-safe surfaces.

Most of us who spend time around animals--either in our home, in the workplace or on the farm--will have  a ringworm infection at some point in our lives. Fortunately in people the infection is usually fairly easy to treat with topical medications. For affected animals, my recommendation is, be aggressive and be vigilant because this particular parasite really bites.

Just Do It! Rabies Vaccination

My veterinary clinic received a call from a frustrated dog owner late Friday afternoon. Her dog was coughing and refused to eat after spending a mandatory ten days in a local shelter under rabies quarantine after biting someone. Her bill for quarantining her dog was over $200. On top of that, now her dog was very sick and faced additional costs for diagnostics and treatment. All this could have been avoided with a comparatively inexpensive examination and rabies vaccination!

Rabies is a disease not to be trifled with. Because rabies disease poses a significant threat to human health, public officials take bite cases involving dogs and cats as well as wild animals very seriously. Wisconsin law requires pet dogs, cats and ferrets that have bitten a person to be quarantined for ten days and examined by a veterinarian three times during this period to monitor for signs of rabies. Although rabies virus is typically transmitted through bite wounds, it is also rarely spread through contamination of open wounds, abrasions, mucous membranes, or scratches with saliva or other potentially infectious material (neural tissue, cerebrospinal fluid, salivary gland tissue). This means that even if a mere cat scratch results in medical intervention for the person scratched, the injury may need to be reported to the authorities with orders to quarantine.

Here's the catch. If the pet is current on its rabies vaccination, the quarantine can occur in the owner's home. If the pet's rabies vaccination has lapsed the quarantine must be in an approved facility such as a veterinary clinic or shelter at the owner's expense. And either way the pet needs to be examined three times by a veterinarian.

Dog showing signs of rabies during quarantine

Animals that develop neurological signs during the quarantine period are humanely euthanized and their brains are submitted to the state diagnostic laboratory for testing. If the animal's brain tests positive for rabies the injured person needs to undergo rabies prophylaxis, the series of injections to prevent development of rabies disease. In the past, these injections were administered into the person’s abdomen. Nowadays, the injections are given in the arm, not much different from getting a tetanus or flu shot!

Did you know?

• Rabies occurs in more than 150 countries and territories. Rabies is found on every continent on Earth except Antarctica!
• Worldwide, more than 55,000 people die of rabies every year. Nearly half of those bitten by rabid animals are children!
• Dogs are the source of 99% of human rabies deaths.
• In the United States, raccoons, skunks, bats, and foxes are common wildlife carriers of rabies. Among domestic animals (besides dogs, cats and ferrets), cattle, horses, swine and other livestock can also be affected by rabies virus.
• Not all rabid animals show the classic foaming-at-the-mouth “mad,” or furious form of rabies. Some rabid animals display the paralytic or “dumb” form of rabies, and may appear to be choking on something. Human exposure in these cases often occurs when a well-meaning person reaches into the animal’s mouth to clear the obstruction!
• Wound cleansing and immunization within a few hours after contact with a suspect rabid animal can prevent the onset of rabies and death.
• Every year, more than 15 million people worldwide receive post-exposure preventive injections to avert the disease – this is estimated to prevent 327,000 rabies deaths annually.

The Center for Disease Control (CDC) provides a good overview on rabies disease. Also, the American Veterinary Medical Association (AVMA) has created an entertaining and enlightening video on rabies which is appropriate for educating young people about the dangers of rabies. 

Just do it! sums up my feelings on rabies prevention. Keep all pets -- even indoor cats -- current on their rabies vaccination. Educate yourself and the children you love about rabies disease prevention. In the case of injury from an animal -- especially wildlife or stranger -- contact the local authorities (police, animal control, physicians, veterinarians) for assistance in determining whether quarantining, testing or prophylaxis is necessary. 

Leapin' Livers! Leptospirosis and Other Liver Problems

I am exhausted. And demoralized.

Since late Thursday evening I have been caring for a critically ill terrier on intravenous fluids. Up every couple of hours each night for potty breaks, medicating and TLC. During the in-between times watching "Doggie TV", my closed circuit camera system broadcasting the antics of hospitalized pets to the comfort of my couch (not very stimulating programming...lots of sleeping going on in the clinic!) Just when I thought he was ready to go home on Saturday, he started to relapse.

Denny* is a six-year-old Cairn terrier who presented for vomiting, diarrhea and not eating. Extensive bloodwork and fecal tests all pointed toward acute liver failure. The liver is a very important organ that comes under attack from all sorts of day-to-day insults. Although the liver has hundreds of vital functions, one function is an all around "detoxifier." Everything that passes through the lips of an animal is dealt with by the liver:  bacteria, viruses, toxins, medications. Most of the time anything with potential to harm is effectively neutralized and silently excreted from the body. Sometimes the liver's defenses are overcome and the animal becomes ill. Luckily the liver also has great regenerative potential, so with some intensive care, elimination of the inciting cause, and time, many of these animals recover fully.

Electron micrograph of Leptospira bacterium

Due to his age and vaccine status, Denny was first suspected of having a bacterial infection in his liver called leptospirosis. This organism is shed in the urine of infected wild animals such as racoons or domestic animals like cattle and dogs. The infection is acquired by drinking contaminated water or snuffling around an area where another infected animal has urinated (the bacteria can pass through mucous membranes such as lips, noses and breaks in the skin). Leptospirosis is a zoonotic disease, meaning people can catch it from their infected animal. Some animals become very sick from liver or kidney disease, while others are asymptomatic carriers of the disease, shedding the bacteria wherever they urinate! Yikes! Although leptospirosis is treatable with common antibiotics, if the infection has triggered widespread inflammation in the system the animal may not respond to treatment.

While there is a specific test for leptospirosis, it takes time to run at the outside laboratory and Denny needed treatment immediately. We started him on intravenous fluids to help flush the buildup of liver toxins from his bloodstream, anti-vomiting medications and antibiotics. By Friday evening he was able to keep down water, small amounts of food made for liver failure patients, and oral medications. He was perky and stronger than when he arrived Thursday evening. He even lifted his leg to pee!

On Saturday morning I made preparations for sending Denny home. But by the afternoon, Denny refused to drink and started vomiting again. And his diarrhea returned, a bright orange color signaling continued problems with his liver. Still bright, Denny clearly is not improving enough to go home.

My heart is sinking. It's not the normal progression of things for uncomplicated leptospirosis. Other differential diagnoses are spinning through my mind as I try to make sense of Denny's disease. Does Denny, though not old, have a liver tumor? Does he have leptospirosis or other infection complicated by raging hepatitis? Does he have a heretofore asymptomatic congenital liver disease such as a shunt, a condition where blood loaded with nutrients and waste products bypasses the liver processing center? I'm dwelling a lot on this last one because I know more about his genetic background than I do most of my patients. His parents are my patients too. And they are nearly twice his size!

Portography, a special imaging technique, showing a
large liver shunt. A special dye is injected into the splenic
vein (from right of image) which then travels to the liver.
Here the dye mostly bypasses the liver (middle)
straight back to the heart (left of image).

This size difference worries me because dogs born with liver shunts are generally smaller than their counterparts and may be "poor doers" throughout life. Severely affected animals may show symptoms early on, but some pets find a way to compensate for the disease and may have little to no sign of disease for years. Maybe they do poorly under anesthesia at the time of spaying or neutering. (This is why preanesthetic testing is so important...to catch any early signs of liver problems before anesthesia.) Maybe they are intermittent pukers or have other easily overlooked symptoms of illness throughout life. Maybe as adults they just have some unexplained liver elevations on wellness blood screening and are acting perfectly happy otherwise.

Denny's owner allowed me to speak with the breeder, who has been able to keep tabs on most of her puppies long after adoption. Turns out Denny was diagnosed with a temporary heart murmur in early puppyhood which later resolved. In addition to being petite, Denny has been intermittently vomiting for years, a medical problem unique to him among his canine family members. She also reports that Denny's brother died at age 5 from a vague illness involving his liver!

Because liver shunts require specialized imaging or invasive biopsies for definitive diagnosis, the expense of which is outside most families' reach, we are left with more questions than answers oftentimes. I'm not sure how Denny's situation will resolve. Time is the nearly magical ingredient in so many of these tough cases. Denny's owners are committed to giving him a good chance, so we will continue IV fluids and symptomatic medications for now, buying his liver more time to rest, regenerate and recover if possible.