Ear Mite
Otodectes cynotis (Hering), Psoroptidae, ACARIFORMES


DESCRIPTION

Adult -- Female ear mites are microscopic (about 0.4 to 0.5 mm), pale mites with cup-like structures at the tips of the front four legs and long setae at the tips of the hind four legs. Male ear mites are smaller (about 0.3 mm) and have cup-like structures at the tips of all eight legs. Males have a pair of copulatory suckers (devices that hold the male to tritonymphs and females) on the lower rear. The third pair of legs has especially long setae near the tip. The fourth pair of legs of male and female ear mites is noticeably smaller than the other legs.

Egg -- The egg is soft, sticky and pearly white at first, but soon dries and sticks to the substrate. The egg is oblong and almost round in cross section and is about 0.2 mm long.

Larva -- Ear mite larvae are microscopic (about 0.2 mm), pale mites with three pairs of legs. The front four legs have cup-like structures at the tips and the hind two legs have long setae at the tips.

Protonymph -- This stage (about 0.25 mm long) has four pairs of legs with cup-like structures at the tips of the first four legs. The last two legs are very small.

Deutonymph -- Deutonymphs (about 0.3 to 0.4 mm long) have only three pairs of legs and two small bumps on the rear called copulatory tubercles. This stage has cup-like structures on the front four legs and long setae on the hind two legs.


BIOLOGY

Distribution -- Ear mites are found wherever their host animals occur.

Hosts -- Ear mites have been found in 2.5 to 3.5% of dogs sampled in one study. Another sample of 113 hounds revealed that 77% were infested. In a survey of dog kennels, 33% were found to have 100% of the dogs kept there infected with ear mites. Of randomly selected cats, 20.2 to 28.4% were infested by these mites. It has been estimated that 75% of all long-haired cats are infested with ear mites. These mites have also been collected from the ears of foxes, ferrets, and hedgehogs.

Damage -- Ear mites evidently pierce the lining of the auditory canal or somehow cause excessive production of earwax which becomes fouled with blood and bacteria. Crusts of earwax and blood form in the auditory canal and outer ear. Host animals scratch their ears excessively which causes loss of hair and scabbing. Secondary bacterial infections sometimes cause fever, depression and sullen, ill-tempered behavior. The ears of infected animals have a noticeable foul odor. Heavily infected animals often shake their heads constantly or run in circles in the direction of the most heavily infected ear. The most spectacularly bizarre behavior occurs when heavily infected dogs or cats are brought out of the cold into a warm room. These poor animals apparently "go beserk" with "spasmodic fits." Symptoms tend to be less severe on older host animals.

Life History -- Ear mites are passed from one animal to another when mites are dislodged during violent shaking of the head onto nearby animals or contact between animals, especially while nursing. However, it has been shown that ear mites also crawl about on the body of infested animals and that they can survive off of the host as long as hair and other detritus from the host animal are present. Thus, this mite passes from host to host with ease in confined quarters. Adult mites live about four weeks. Eggs hatch in 3 to 4 days and each active developmental stage lasts about one week and is followed by a 24 to 36 hour resting stage. Development from egg to egg laying female takes about three weeks. Ear mites tend to wedge under the edges of scabs for shelter.

Ear mites can be reared successfully from cells, hair, and dried earwax scraped from the ears of host animals. Once the ears of infested animals are secondarily infested with bacteria, the mites leave the suppurating area and tend to infest the outer ear or skin around the eyes. These facts indicate that ear mites do not feed on fluids.


CONTROL

Because ear mites pass readily from one animal to another in confined quarters, one might consider boarding a pet with a neighbor rather than a commercial kennel should it be necessary to leave the animal. Pets which have a fetid odor associated with the ears or which shake or scratch their ears excessively should be examined for signs of ear mites. If the inside of the outer ear is dark with dried scabs and the auditory canal is filled with dark, thick earwax, the chances are great the pet is infested. Examination of material from the ears by a veterinarian will confirm the presence or absence of ear mites. One type of treatment consists of washing the auditory canal with an alcohol based solution of "ear cleaner." After the pet has removed the solution by violent shaking of the head, an emulsion of a miticide, antibiotics and mineral oil is dropped into the auditory canal to kill the mites, stop any secondary bacterial infection and to soothe the ears. Such a treatment should be applied several times as prescribed by the veterinarian. If a pet has mild symptoms, the application of mineral oil alone to the auditory canal is sufficient to control ear mites.