Ectoparasites we might find in a pet’s ear canal using microscopy!!

Our last post looked at some of the micro-organisms involved in ear infections that we can see under the microscope…rods, cocci and yeasts.  Sometimes looking down the microscope we find ectoparasites from an ear swab sample . Ectoparasites mean parasites that live on the external surface of an animal – like fleas.  But some of these ectoparasites live on the lining of the ear canal – best known as ear mites. To look for ectoparasites we use a slightly different technique in preparing the microscope slide.  We add a small amount of liquid paraffin to the ear swab on the slide.  We also change the settings on the microscope to a lower light intensity and use a lower magnification lens.  Sometimes we also add dilute potassium hydroxide liquid to a plain sample on a slide to allow us to see any parasites more clearly.

You can see why ear mites must feel very itchy



Fig 1 shows a clip of a fresh liquid paraffin mounted sample from a cat’s ear.  It shows Otodectes cynotis mites, more commonly known as ‘ear mites’.  The life cycle of Otodectes cynotis is around 3 weeks with eggs being laid in cement like material that sticks them to their surroundings.  They hatch into 6 legged larvae after about 4 days. The 6 legged larvae feed and rest before becoming 8 legged adults capable of mating and producing further eggs.  Adult mites can expect to live approximately 2 months.  They can survive away from their host for 5 to 17 days in the animal’s environment.

They are most often found in the ears of cats and sometimes dogs, but can be found on your pet’s skin surface.  Clinical signs of cats suffering from mites vary.   Some are very itchy with a discharge reminiscent of coffee grounds.  Dogs may have very itchy ears with minimal discharge.

Ear mites can be shared between dogs and cats and are very contagious.  Many of the newer flea products will help to treat them and prevent them from becoming established.  Check with your own vet which ones will help.

But not all mites look the same

The second picture shows Demodex mites taken from an ear sample.  Sort of cigar shaped.  These mites are more commonly associated with skin disease but can occasionally be found within the ear canal.  They are usually associated with a waxy discharge.  Demodex canis, the main form found in dogs, is passed from the bitch to her pups within the first few days of life and is considered a normal inhabitant of the skin.  Demodicosis describes the condition in which the Demodex mites multiply in excess causing skin and occasionally ear problems.   Certain breeds have a higher risk of developing demodicosis.   Genetics are known to play a part in the disease process.  But so are problems with the immune system due to factors such as a young age or concurrent illness.  The life cycle is completed in 3 to 5 weeks and, apart from Demodex gatoi in the cat, the mite is not considered to be contagious.

Are you worried about your pet’s ears, especially if the problem is not getting better or keeps coming back?  Further investigation may well help solve the problem for you.  Feel happy to contact Nicky Shaw for help.  With her Advanced Practitioner Status with a Veterinary Dermatology Designation she will always be happy to go that extra mile to help you and your pet.