Overview
Otodectes cynotis are surface-living mites affecting the ear canal and pinna. Cats more often suffer from parasitic otitis than dogs, however both are affected. Puppies and kittens are more likely to be affected following infection from the mother at the time of feeding. The mites are spread by direct contact between animals and feed on debris and tissue fluid in the ear canal and local area.
Clinical signs
These mites cause direct irritation from feeding activity and secondary hypersensitivity inflammatory reaction to mite products. The most common clinical sign is ear irritation – scratching, rubbing and head shaking. Thick black crumbly "coffee ground" discharge in ear canal and inflammation and thickening of ear canal. Self-trauma may result in the development of secondary pyotraumatic dermatitis around the head and ear base.
Diagnostic investigations
White mobile mites visible on magnified otoscopic examination.
Positive identification of Otodectes cynotis on ear swab microscopy.
Treatment
Ear cleaning. Many topical medications are inactivated by wax and discharge within the ear, and so ear cleaning is essential prior to administering topical medications. Teach the owner how to clean the ear canal with a suitable ceruminolytic cleaner to remove wax and discharge.
Systemic treatment. Use of systemic drugs rather than topical therapy ensures Otodectes cynotis on other areas of body will be killed.
Selamectin spot-on solution. 6mg/kg applied topically. Part the hair on the back of the neck and apply directly to the skin every 4 weeks. Only use in puppies > 6 weeks old.
Moxidectin spot-on solution (with Imidocloprid). 0.1ml/kg applied topically every 4 weeks; use dosing pipette appropriate for size of dog.
Miticidal ear drops – most licensed ear drops have miticidal claims.
Ivermectin 200 - 300µg/kg s.c. or p.o. every 2 weeks for 6 weeks (off-licence and not to be used in Collie or related breeds of dogs – risk of serious drug reaction). May also be used topically 1% ivermectin diluted 1:9 with mineral oil (2-4 drops in ear daily for 3 – 4 weeks).
Secondary infection. Treatment of secondary bacterial or yeast otitis externa with ear cleaning and appropriate topical treatment.
Prognosis
Successful elimination with appropriate treatment.
Prevention
Treatment of all in-contact animals simultaneously.
Treat for full life cycle of mites (21 days) – repeat treatment after 10 days.
Links
Further information on this subject is available on the ESCCAP website.