Ear Mites

The Parasite

They live on the skin surface rather than burrowing, and may occasionally be found on the adjacent skin of the head.

The mites feed in the outer ear canal, causing irritation of the epithelial lining. The canal becomes full of cerumen, blood and mite feces, giving rise to a characteristic otitis externa of parasitic origin. Occasionally mites may be found on the adjacent skin of the head. Adults are large and white.

Females are 500 x 300 µm in size. The first two pairs of legs for all stages bear unjointed, short stalks and suckers (Fig. 1), while only the males have suckers on the rear legs. Male adults are 395 x 295 µm in size (Fig. 2).

Fig. 1: Otodectes cynotis female with a visible egg

Fig. 2: Otodectes cynotis male

Life Cycle

The life cycle of Otodectes is similar to that of all other mites, i.e. development from egg to adult via a larval and two nymphal stages. Development time is about 3 weeks.

Otodectes larvae feed for 3 to 10 days, rest for a short time and then molt to become a protonymph. This nymphal stage is rather short and leads to the telonymph; once the female reaches this stage copulation occurs with an adult male mite. Fertilization only occurs, however, after the female telonymph has molted to become an adult female.

The life span of adult mites is about 2 months. Young animals are most susceptible to infestation and, as the mites are highly contagious and not host-specific, all in-contact animals should be presumed to be infected.

To watch or download the animation of this life cycle please visit our download area.

Pathogenesis and Clinical Appearance

Otodectes mites feed in the outer ear canal and cause irritation of the epithelial lining. The canal becomes full of cerumen, blood and mite feces and gives rise to a characteristic otitis externa of parasitic origin.

Although the clinical symptoms may vary, Otodectes are often seen in cats. The amount of discharge present is not always related to the severity of clinical signs – some cats with heavy discharge show no signs, whereas others with minimal discharge have intense pruritus.

The ear mite is very annoying to the host animal. The physical presence of the mite induces a mechanical irritation that accounts for some of the pruritus, but, in addition, mite saliva is an irritant and immunogenic. There is no delayed hypersensitivity, but reaginic antibodies develop early during infestation, followed by precipitating antibodies. The presence of an IgE-like antibody in the cat suggests that hypersensitivity also contributes to the pruritus.

Fig. 4: Typical debris in the ear of a cat infected with ear mites Fig. 5: A healthy ear following treatment with Advocate®