Otitis externa caused by an exotic organism – Otodectus cynotis

A 39-year-old painter referred from ear, nose, and throat presented with a scaly patch with crusting on the upper helix of the left ear suggestive of otitis externa [Figure 1]. There was no seborrhea. A scrapping mounted on potassium hydroxide demonstrated a mite identified by the entomologist from the mouth biting parts and forward appendages as: Otodectus cynotis [Figure 2]. This mite belongs to the Psoroptidae group infesting the ears of cats and dogs and is transmitted to humans by close contact with pets, causing otitis externa and a scabies like infestation. Our patient did not give a history of any contacts with pets, but transmission through fomites such as furniture is reported.^[1] Our patient was a painter and had visited many houses, some with pets, and it is possible that he was infested by fomite transmission. The patient was started on ivermectin 12 mg/day orally, antibiotics, and topical mometasone. Antiparasitic drugs such as moxidectin, selamectin, and imidacloprid are used by veterinarians for pets.^[2] We could not find any similar report in a review of English literature to the best of our knowledge.

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Figure 1:

Scaly patch on left ear.

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Figure 2:

The mite Otodectus cynotis demonstrated in 10% potassium hydroxide mount test.

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