The Cat Area 8: Otodectes Cynotis

Good day friends and colleagues, today we will talk about the main source of ear mites not only in cats, but also in dogs.

Otodectes Cynotis, this mite has been proven to be found in dogs, ferrets, foxes, and of course, cats. It is found all around the world, America, Europe, Asia, Middle East and Australia.  

The mites live in the ear canal of the cat. Most times there can be over a thousand mites present in the ear without any apparent mites appearing on the surface of the feline host.

Now we must remember the life cycle of these mites. First of all, the female mite secretes a fluid that helps her eggs to be glued onto the cat's ear canal. The eggs typically require 4 days of incubation prior to hatching. The life cycle includes a larva, a protonymph, and a deutonymph. Each stage takes a minimum of 3 to 5 days to develop, and the development is followed by a quiescent period of about 24 hours during which time the mites molt and shed their cuticles. As soon as the adult emerges from duetonymph cuticle, it will seek out and form a pair with a deutonymph. The complete egg to egg cycle took aproximately 18 to 28 days (about 3 weeks).

Transmission between hosts is by direct contact. The mites seem to require a relatively high humidity for survival and seem to rapidly dessicate at typical room humidities.

As for the clinical signs and pathogenesis, most cats tend to scratch a lot, however, some cats vary in their abilities to serve as hosts for Otodectes cynotis. If we observe close enough we can see that most cats can have severe lesions with significant quantities of dark cerumen and sometimes even blood present in their ears but one or two mites, other cats will have very clean ear canals, almost devoid of cerumen and detritus but have lots of mites. Still other cats can host huge numbers of mites in their ears and still have shown very little in the way of outward signs of infection. Ears of cats with very large numbers of mites tend to contain a dry waxy parchment-like material that occurs as sheets throughout the ear canal. These layers of sheets will contain mites throughout and consist in part of rafts of eggs that are embedded in the material. These ears tend to not contain large quantities of wax.

The easiest way to diagnose Otodectes cynotis is with an otoscopic examination, by observing movement. Another way to diagnose is with a swab in the ear with a cotton tipped applicator and to place the swab in a glass vial serum vial with a small drop of water or even baby oil. After about an hour, the mites will begin to migrate out of the cerumen and dentritis and can be observed walking on the walls of the glass vial or on the applicator stick. Smearing the ear swab onto a glass slide and examining under 400 X magnification usually reveals the mites too.

The Identification is relatively simple, no other non-burrowing mites of large size are typically found in the ears of the cat. The living mites appear as small white organisms that can be seen moving about within the ears or on swabs of deteritus removed from the ears. An examination of the distal portions, pretarsi, of the anterior pairs of legs will reveal the 'wine glass' shaped caruncle on a short pedicel.  The eggs are white, oval, slightly flattened on one side, and are 166 to 206 µm long.

As Veterinarians we have now days multiple options regarding treatment for otodectes cynotis, and of course as we know, not all patients can react properly to a certain treatment, and that is why, it is our job to test and provide the best treatment for each patient.

Our best chance on treatment can be Pyrethrin, there are several presentations containing different type of compounds, such as Otomite Allerder by Virbac, Nolvamite by FortDodge, Eradimite by Solvay, Aurimite by Schering Plough. Also we can use Rotenone containing compounds such as Er Miticeby Phoenix, Ear Mite Lotion by Durvet, Ear Miticide by Vedco.

If we want to go beyond, because our patient has a greater infection we can also use Otomax, which is a mineral-oil based otic ointment containing gentamicin sultate, betamethasone valerate, and clotrimazile.

However, if our patient is not too infected, or if the patient has shown in previous ocasions to be picky on the meds, we can also do a test using natural products such as 2ml of mineral oil based and 30 seconds of external massage of the base of the ear of the cat, and we can see if after 2 treatments one week apart we are able to see a difference. Of course if we decide to go all natural with the mineral oil, we might notice that this oil might tend to leak from the ear, and the hair on the head of the cat might appear oiled for the first day or so after treatment.

And of course as we all know, when it's about a fiery cat we can always go with shots, Ivermectin injectable, even if is not officially approved in cats, ivermectin has been used to treat feline infestations with otodectes cynotis. The most typical dosages are 0.2 to 0.225 mg/kg injected on one occasion or on two occasions with a 3 week interval between injections.

As Veterinarians we most be aware of the toxicity of Ivermectin when used not just in cats but in dogs too, 0.5mg / kg body might just be the limit of this medication, any more than this and it can become extremely toxic. However, Ivermectin can be used safely into the ear canals in drop presentation, it really is highly effective!

Also, we most remember, that one dosage of medication, which ever we choose for our patient may not be enough, and we most tell the owner that they need to return within 2-3 weeks for a follow up visit, and then we most check our patient again and see if there's been improvement.

Now let's talk about the hazzard towards humans, there is a slightly chance for this mite to be transferred to humans, since 1978, there haven't been any reports, so in few words, it can be hazzard towards humans, however is very rare.

It is very important to remind the owner of our patient, that if they have any other pets at home, they should treat all of them, since ear mites can be easily transmitted among them, even if it's a dog or a rabbit, or a ferret, even a parrot.

We hope that this post is of some sort of help for you, or as a kind reminder since ear mites are very common among cats and dogs.
Cheers!




MVZ Carolina Pruneda