Your dog keeps scratching at one ear and shaking his head. Your cat's ears are packed with dark, crumbly debris. Both are classic reasons to suspect ear mites, Otodectes cynotis, and both are reasons to book a vet visit rather than guess, because yeast and bacterial ear infections can look the same. If mites are confirmed, every dog, cat and ferret in the home needs treating, not just the one that is scratching.
What Are Ear Mites?
Otodectes cynotis is the ear mite behind most ear mite cases in cats and dogs. It is a tiny arachnid that lives in the external ear canal, the tube that runs from the ear flap down to the eardrum. It is a surface mite: it does not burrow into the skin, and it feeds on skin debris and tissue fluid on the lining of the canal. Some mites wander out of the ears onto the head, neck, rump or tail.
Who gets them
Cats, dogs and ferrets, plus wild carnivores such as foxes. Ear mites are more common in cats than in dogs, especially kittens under a year old and feral cats. Rabbits get ear mites too, but that is a different species (Psoroptes cuniculi).
How they spread
Mainly by close contact between animals, which is why a mother often passes them to her kittens or puppies. Bedding and grooming tools may carry mites for a short time, but mites do not survive long off the host, and CAPC does not consider the environment a significant source of spread.
Life cycle
The whole cycle happens on the host and takes about three weeks (CAPC gives 18 to 28 days from egg to egg). The stages are:
- Egg, cemented to a hair or the skin surface
- Six-legged larva, which hatches after a few days
- Protonymph
- Deutonymph
- Adult
There is no pupal stage. Adults are thought to live up to about eight weeks and keep reproducing throughout that time, so numbers build quickly.
Can people catch ear mites?
Rarely. People who live with an infested pet occasionally get a temporary itchy rash, and there are a few published reports of the mite in human ears. It is not considered a major zoonotic risk, and getting rid of the mites on the pets solves the problem.
Symptoms of Otodectes Cynotis
Signs vary a lot from one animal to the next, and they do not track the number of mites. Some cats carry huge numbers with few or no signs, while others have badly inflamed ears with only one or two mites. For veterinary teams: most of the signs come from a hypersensitivity reaction to antigens the mites produce while feeding, which helps explain that mismatch.
When signs do show, they can include:
- Scratching or rubbing at the ears
- Head shaking
- Dark brown or black discharge that looks like coffee grounds
- An ear canal filled with dark, waxy or crusty debris
- Redness and inflammation of the ear canal
- Scratch marks, crusts, or hair loss around the ears from self-trauma
- Head tilt or circling in some animals
- A swollen, fluid-filled ear flap, called an aural hematoma, caused by vigorous head shaking and scratching
- A bad smell, which usually points to a secondary bacterial or yeast infection
Diagnosis of Otodectes Cynotis
The history and signs, especially an itchy pet that lives with other itchy pets, make a vet suspect ear mites. The diagnosis is confirmed by finding the mites.
Your veterinarian will usually:
- Look down the ear canal with an otoscope (a lighted scope for examining the ear), where live mites may be seen moving. For students and new techs, our guide on how to use an otoscope covers the technique.
- Collect ear debris and check it under a microscope for mites, eggs or mite fragments.
- Sedate the pet if the ears are too sore to examine properly.
A quick look with the otoscope can miss mites. In a small 2019 study of 30 infested ears in 5 dogs and 12 cats, otoscopy alone found mites in 20 of 30 ears (67%). Debris collected with an ear curette and checked under the microscope found them in 28 of 30 (93%), and the two methods together found all 30. So a look that finds nothing does not fully rule mites out.
Ear mites vs. other ear problems
Dark debris is not proof of mites. Yeast (Malassezia) and bacterial ear infections can look very similar, and they often occur alongside mites as secondary infections. A microscope check of the debris tells them apart, and it decides which treatment makes sense.
What Do Ear Mites Look Like?
Adult ear mites are about half a millimeter long or smaller, roughly the size of a grain of sand. Females are slightly larger than males and may just be visible without magnification, as tiny white specks that move against the dark debris. Adults have four pairs of legs. They have no wings and cannot fly or jump, but they move quickly over the surface of the ear canal.
When to See Your Vet
Any of the signs above is a reason to book a visit, and so is pain when the ear or head is touched. Have new kittens, puppies and rescued pets checked too, especially if they will live with other animals.
Leave cleaning and medicating the ears until the vet has examined them. Aggressive cleaning can make an inflamed ear worse, a badly inflamed ear can have a damaged eardrum, and the right product depends on what the vet finds.
Treating Ear Mites
Treatment works well when the whole plan is followed. Your veterinarian chooses the product and dose for each animal based on species, age, the severity of the ear disease, any secondary infection, and how many pets are in the home. A typical plan includes:
- Ear cleaning by the vet team, or at home only as your vet directs. If the ears are very painful, cleaning may be done under sedation.
- An anti-parasite product. Options include products in the macrocyclic lactone or isoxazoline classes and pyrethrin ear products. Treatments that work through the whole body are often preferred, because mites can live outside the ears.
- Treatment of secondary infections. If bacteria or yeast are present, your vet may add an antibiotic or antifungal.
- Every dog, cat and ferret in the household, whether or not they show signs. An untreated housemate can pass mites straight back to a pet that has just been treated.
- A recheck, so your vet can confirm the mites are gone.
Wash your pets' bedding and clean grooming tools during treatment. House sprays are generally not needed, because mites survive poorly off the host.
Preventing Ear Mites
Many broad-spectrum parasite preventives in the macrocyclic lactone and isoxazoline classes, the same products used against fleas, ticks and other parasites, also protect against ear mites. Ask your veterinarian which one suits each of your pets.
Beyond that, prevention comes down to contact. Get new and outdoor pets checked before or soon after they join the household, and treat all in-contact animals when one is diagnosed.
Summary
Otodectes cynotis is the common ear mite of cats and dogs. It lives on the surface of the ear canal, spreads by close contact, and can hide in pets that barely scratch. Treatment is usually effective. What tends to trip owners up is an untreated housemate or a skipped recheck.
If you like this article, read more on our blog!
Sources
- CAPC: Otodectic Mite
- Merck Veterinary Manual: Mange in Dogs and Cats
- WCVM Learn About Parasites: Otodectes cynotis
- Today's Veterinary Practice: Ear Mites: Uncovering, Treating, and Preventing Infestations
- PubMed: Comparison of three methods for the diagnosis of otoacariasis due to Otodectes cynotis in dogs and cats
This article is for general information and is not a substitute for advice from your veterinarian.
