Ear mites is one of the most common causes of otitis externa in our domestic carnivores. Without seriousness, it can nevertheless lead, if not treated, to otitis interna.
Causal agent and clinical signs
The causative agent is Otodectes cynotis, a mite that lives in the animal’s ear canal. This mite measures 350 to 500 micrometers.
The mites feed on the inflammatory exudate caused by the bites they inflict on the epidermis of the ear and also on the cerumen produced.
Adults lay eggs in the dog’s external auditory canal; the complete cycle takes place in 14 to 21 days.
The transmission of ear mites from animal to animal occurs through direct contact. In some cases, it can also be done by indirect contact when the animals use the same sleeping places. Otodectes can leave the ear canal, which explains the bilateral involvement in infested animals, but also the contagiousness of ear mites.
The most frequently observed clinical signs are ear pruritus (very severe itching) and profuse blackish, smelly discharge in the ear.
The dog may shake its head very often or keep its head tilted to one side (usually on the side most affected). An auriculo-podal reflex (the dog scratches the ear very sharply with the paw) is frequently observed when a cotton swab is introduced into the ear.
Ear mites in dogs usually cause otitis externa, which is inflammation of the external ear canal. If this scab is not treated, it can progress to purulent otitis externa, or even otitis interna. The transition to chronicity (infection that lasts more than 3 weeks) can cause narrowing of the external auditory canal.
The diagnosis is usually made by the veterinarian by observing the ear canal with an otoscope. Mites and the inflammatory lesions they cause are visible in the ear canal.
A sample of the secretions and their observation under a microscope generally make it possible to highlight the causal agent: Otodectes cynotis.
Your veterinarian will thus differentiate between ear mites and other agents responsible for ear pruritus such as Demodex canis (rare) or Malassezia pachydermatis.
He will also observe your dog’s eardrum to make sure there are no complications.
It can happen that the dog, by untimely scratching of his ear, ruptures an auricular vessel and generates an othematoma. In this case, the initial cause, namely scabies, must be treated before considering treatment for the othematoma.
Treatment and prevention of ear mites
The treatment of scabies consists of the regular application of an acaricide by local route for a minimum duration of 21 days (duration of the cycle of the mite).
In more specific cases, topical fipronil or subcutaneous injection ivermectin may be used. Topical selamectin has also been reported to be effective.
Interspecific transmission of ear mites is possible: it can thus pass from dogs to cats (and vice versa). However, it is not a zoonosis, humans cannot catch it.
Due to the high contagiousness and the possibility of interspecies transmission, when one of the animals in the house is diagnosed with Otodectes cynotis, it is recommended to treat all animals, especially if they are in close contact. the ones with the others.
The best prevention of ear mites relies on good ear hygiene (without being excessive). In addition, treatments by the cutaneous route or by the oral route allow optimal prevention. New molecules recently put on the market, in particular sarolaner and its derivatives, have shown significant efficacy in the prevention and treatment of ear mites in dogs.
Ear mites is a common condition in dogs. Your veterinarian is in the best position to advise you on the treatment to be implemented but also to guide you towards the most effective prevention according to your dog’s size and lifestyle.