Current Advice on Parasite Control:
Ectoparasites - Otodectic Mite (Ear Mite)
Otodectes cynotis (ear mite)
Otodectes cynotis has been reported from dogs, cats, foxes, and ferrets worldwide.
Overview of Life Cycle
- The complete egg-to-egg cycle takes 18 to 28 days. The egg hatches to produce a larva, a protonymph, and a deutonymph. Each stage takes a minimum of about three to five days of maturation to reach the next stage. The pairing of the male and a deutonymph takes place, and fertilization occurs as soon as the female molts to the adult stage.
Video courtesy of Dr. Chris Adolph, Southpark Veterinary Hospital
- Eggs are large (about 200 μm in length).
- A six-legged larva hatches from the egg and goes through first and second nymphal stages before becoming an adult.
- Adult females are 350 to 450 μm in length, and adult males are 275 to 360 μm in length.
- The adult male has short pretarsi with wineglass-shaped caruncles on the distal end of each leg. The female has caruncles on only the first two pairs of legs, with long hairs on the posterior two pairs of legs. The posterior of the male has a pair of suckers used to grasp the female during copulation.
- Clinical signs include shaking of the head, scratching at the ears, inflammation of the ear canals, and accumulation of copious cerumen and frequently serous to purulent exudates, depending on the nature of secondary infectious agents.
- In very heavy infestations, mites may leave the ear canal and cause infestations on the head and associated body parts of the dog or cat. In rare cases, these animals may present with miliary dermatitis.
- Cats may have what appear to be significant lesions with large quantities of dark cerumen and even blood in the ear canal, yet only one or two mites are present. Other cats may have very clean ear canals and as many as 50 mites present. Still other cats may have thousands of mites in an ear and yet exhibit few, if any, outward signs. The ears may be filled with a dry and waxy parchment-like material that occurs as sheets throughout the ear canal.
- Infestations are not uncommon in dogs and cats that do not receive routine veterinary care.
Host Associations and Transmission Between Hosts
- Infestations in dogs or cats can be transferred between hosts by close contact.
- When mites are present in one dog or cat in a household, it is essential that all dogs and cats in the household be treated at the same time.
Prepatent Period and Environmental Factors
- The prepatent period is unknown, but the complete life cycle takes approximately 18 to 28 days.
Site of Infection and Pathogenesis
- Mites live routinely in the ear canal. Cats can have more than 1,000 mites per ear; the numbers present in dogs are usually much lower.
- The ear canal epithelium becomes hyperkeratotitc and hyperplastic. with dramatic hyperplasia of the ceruminous and sebaceous glands. There is a marked increase in mast cells and macrophages, and the venules become dilated. Animals developed IgE levels to the infestation about two weeks after becoming infested.
- Mites in the ear may be observed with an otoscope or on swabs of the ear canal.
- Labeled products for cats include topically applied moxidectin/imidacloprid and selamectin. Cats may also be treated with labeled products containing ivermectin or milbemycin that are formulated for direct application to the ear canal.
- Labeled products for dogs include topically applied selamectin. Moxidectin/imidacloprid has been shown to be efficacious for ear mites in dogs.
- Cleaning of the ear canal is always recommended.
- When secondary infections with bacteria or fungi are suspected, these conditions should also be treated.
Control and Prevention
- Routine, monthly treatment with topical moxidectin/imidacloprid or selamectin should prevent ear mite infestations in both dogs and cats.
Public Health Considerations
- On very rare occasions, people have been infested with ear mites. One report cited ear mites on the torso and extremities of the new owner of a cocker spaniel. In another report, six mites were recovered from crusts on a woman’s eardrum.
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