Otodectes cynotis

Otodectes cynotis
Phylum	Arthropoda
Class	Arachnida
Order	Astigmata
Family	Psoroptidia
Genus	Otodectes
Species	O.cynotis

Also known as: Ear mite

Otodectes cynotis C. Antonczyk 2008

Otodectes cynotis Caroldermoid 2006, wikimedia commons

Introduction

Otodectes cynotis mites are surface mites. They are the cause of otodectic otitis, the most common mange of dogs and cats in the world. They are also found in the fox and the ferret. The mites inhabit the inner ear and feed on ear debris, they appear white in colour.

Pruritus is caused by irritation and the saliva of the mites, which is immunogenic. Secondary bacterial infection is common, resulting in purulent otitis externa which will require more treatment.

In cats, another presentation can be seen, which is that of an ectopic infection where signs are seen on other body parts such as the tail. This is due to contact e.g. cats sleeping in a curled position would allow mites to infest that area. Transmission of the mites can occur to kittens whilst they are suckling.

Identification

The mites have closed keratinous bars, apodemes on their ventral surface. They are smaller in size than psoroptes cuniculi and have short pedicles on their first and second pairs of legs.

Lifecycle

The Life cycle of an Otodectes mite takes 3 weeks. The females lay around five eggs a day on the surface of the ear canal. Four days later, larvae hatch and become nymphs. There are two nymphal stages before an adult mite is formed.

Clinical Signs

Clinical signs include head shaking, scratching of the ear and even the development of an aural haematoma because of the two above signs. The animal may often resent this area being touched.

A brown waxy exudate is produced and this later becomes crusty. If secondary bacterial infection has occurred then pus will also be seen in the ear canal.

Diagnosis

Clinical signs and history are indicative of the disease.

Visualisation of the mites via an auroscope will provide definitive diagnosis.

Treatment

Topical ear drops usually contain acaricide, fungicide, antibiotics and steroids. These should be dropped into the ear and the base of the ear then massaged to help the drops disperse. In cases of severe wax build up, ceruminolytics may be useful.

Selamectin as a spot on also acts to prevent Otodectes.

All in contact animals should be treated in the household as these may be asymptomatic carriers.

References

Blood, D.C. and Studdert, V. P. (1999) Saunders Comprehensive Veterinary Dictionary (2nd Edition), Elsevier Science.
Bond, R. (2008) Dermatology Study Guide, Royal Veterinary College.
Foster, A, and Foll, C. (2003) BSAVA small animal dermatology (second edition), British Small Animal Veterinary Association
Fox, M and Jacobs, D. (2007) Parasitology Study Guide Part 1: Ectoparasites, Royal Veterinary College

Also see:

Ear Mites in Cats and Dogs

Ear Mites in Ferrets

Otodectes cynotis Learning Resources
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