Ear mites are a common parasite of the cat, responsible for causing otitis externa.
Infection is normally attributed to cat's habit of lying in warm wood shavings under trees, where the mites normally live. Otodectes infection is relatively contagious due to cat's proclivity of sleeping together. Otodectes spp infection in cats occurs worldwide, accounting for up to 25% of consultations in feline dermatology. Transmission is by direct contact and occurs most likely in the neonatal period. Young animals are therefore more susceptible. This mite is not host-specific and also causes otitis externa in the dog and ferret. Transmission to humans may cause pruritus of the arms and trunk.
Mites are usually found deep in the external ear canal, but occasionally are seen on the body.
Clinical signs include head shaking, continual ear scratching, and ear droop. Pruritus is variable. Purulent inflammation and discharge of the external ear (otitis externa), and possible perforation of the tympanic membrane may be seen in severe cases (otitis interna). Pruritus is usually severe, likely to be attributed to hypersensitivity by immunoglobulin E antibodies directed against antigens released by the mite. Self-induced erosions are observed around the ears and aural haematoma are often seen. If the tympanic membrane is ruptured, vestibular syndrome is sometimes observed. Non-specific pruritic lesions on the face, neck and dorsolumbar region, presenting as miliary dermatitis or symmetrical alopecia, are typical. Sometimes, the body is affected without involvement of the ear canals.
Other causes of facial pruritus may need to be excluded in the diagnosis.
Affected animals should receive appropriate parasiticide treatment in the ears and on the whole body for 2-4 wk.
- Ivermectin and selamectin have shown reliability over the years, applied parenterally, topically to ears or as a proprietary 'spot-on'.
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- August, JR (2006) Consultations in feline internal medicine. Vol 5. Elsevier Saunders, Philadelphia
- Shanks, DJ et al (2000) The efficacy of selamectin in the treatment of naturally acquired aural infestations of Otodectes cynotis on dogs and cats. Vet Parasitol 91(3-4):283-290
- Nunn-Brooks, L et al (2011) Efficacy of a single dose of an otic ivermectin preparation or selamectin for the treatment of Otodectes cynotis infestation in naturally infected cats. JFMS 13:622-624