Otodectic mites are tiny insects that live in the ear canals and feed by piercing the skin. They are highly contagious to cats and dogs, but not to humans. Ear mites are the most common cause of ear symptoms in puppies and young adult dogs. Suspect ear mites when both of the dog’s ears are involved.
Ear mites should not be confused with the mites that cause sarcoptic mange. This is an entirely different disease, but one whose signs can include crusty ear tips (see Scabies, page 126).
It takes only a few ear mites to produce a severe hypersensitivity reaction that leads to intense itching with scratching and violent head shaking. The ear flaps become red, excoriated, crusted, and scabbed. The canals contain a dry, crumbly, dark brown, waxy discharge that looks like coffee grounds and may have a bad odor due to secondary infection.
Ear mites can be identified by removing a specimen of wax with a cotton-tipped applicator and looking at it under a magnifying glass against a black background. Mites are white specks, about the size of the head of a pin, that move.
Treatment: Once the diagnosis has been made, all dogs and cats in the household should be treated to prevent reinfestation. If you have a house bunny or ferret, check their ears as well. The ears must be cleaned as described for external otitis. This is essential. Dirty ear canals provide wax and cellular debris that shelter mites and make it difficult for ear medications to contact and destroy them.
After cleaning, medicate the ears using a miticide ear preparation prescribed by your veterinarian. Most preparations contain pyrethrins and thiabendazole. Commonly used ones are Nolvamite, Cerumite, Mitox, Acarex, and Tresaderm. Tresaderm contains a miticide, an antibiotic, and a steroid to relieve itching. Use according to the manufacturer’s instructions.
Revolution is a flea control product that is also effective against ear mites and approved for use in treatment and prevention. Ivermectin may be used as an off-label medication for treating tough cases of ear mites.
It is important to complete the entire course of treatment. If treatment is stopped too soon, a new crop of mites will reinfest the dog.
During treatment, mites escape from the ear canals and temporarily take up residence elsewhere on the dog, causing itching and scratching. In addition to treating the ear canals, the entire dog and all animals that come in contact with her should be treated weekly for four weeks using a pyrethrin-based shampoo, a pyrethrins-based flea powder, or Revolution.
Mite infections are often complicated by secondary bacterial otitis. When present, treat as described for external otitis.