Dog - Mange 2. Otodectic Mange

What is mange?

Mange is a parasitic skin disease caused by microscopic mites. Three different types of mite can commonly cause problems in dogs:-

The otodectic mite usually infests the ears and can result in otodectic mange. This causes irritation leading to bacterial infections which can result in otitis externa.

The demodectic mite usually resides in the hair follicles of the skin and can cause demodectic mange. This is the most common form of mange in dogs.

The sarcoptic mite is responsible for canine scabies (sarcoptic mange). It lives just under the skin.

What is the cause of otodectic mange?

Otodectic mange, also known as parasitic otitis, or ear canker, is caused by Otodectes cyanotis, a large white mite that lives on the surface of the lining of the ear canal and occasionally on the skin surrounding the head or other parts of the body. It, like the demodex mite which on rare occasions can also be responsible for parasitic otitis, is one of the most common mites found on dogs but is reported to account for only approximately 10% of the inflammation of the external ear canal (external otitis) in the dog. This may be an under estimation since the mite becomes difficult to demonstrate once secondary bacterial inflammation is present. This usually follows rapidly as a result of the scratching and rubbing resulting from the irritation caused by the mite.

What are the signs?

Irritation, head shaking and rubbing with abundant brown or black waxy discharge are the most common signs associated with this disease. The ear canal is usually very itchy to the touch and both ears are usually affected. The head shaking, rubbing and scratching may lead to development of aural haematoma (separate handout). The secondary bacterial infection can lead to facial eczema as well as severe inflammation (otitis) of the ear canal.

Is it contagious?

Transmission is by close direct contact although mites are reported to survive in the environment. Young dogs are more prone to infection but not all develop signs. Carriers can still pass the problem on through close contact.

How is my dog likely to have picked up mites?

The problem may have been passed on from the mother during suckling or from other dogs or cats with which your dog has close contact.

Do cats show symptoms if they have ear mites?

Like dogs it varies with the individual. Some cats can carry large numbers of mites without showing obvious signs whereas others will rapidly develop an acute hypersensitivity reaction with typical signs of excess brownish/black wax and acute irritation of the ear canals.

How is it diagnosed?

Microscopic examination of samples of the waxy discharge will usually reveal evidence of the mites. In the ear canal these live beneath the wax next to the skin.

What is the treatment?

It is important that you treat not only the affected dog but all in contact animals in the home. The affected dog will initially require gentle, thorough cleaning of the ear which may have to be done by us under sedation or even a general anaesthetic. Then regular treatment of the ear canal will be necessary. We will supply appropriate medication and explain its use.

In contact dogs and cats that are not showing symptoms may be effectively treated using an appropriate spot-on preparation which we will be happy to supply.

How long will treatment have to continue?

This depends upon the severity of the otitis. It is important that treatment is continued for at least three to four weeks after all the symptoms have resolved.

What is the prognosis?

Otitis of whatever cause is always a potentially serious problem in the dog. There is the danger that the ear drum perforates and inflammation spreads to the middle ear (Otitis media).

Appropriate treatment usually carries a good chance of cure but it is important that the full treatment course is completed according to instructions. Please carry out regular checks to detect any signs of excess wax, sensitivity or smell.

For further information please refer to the handout on Otitis externa.