Case summary A 7-year-old male domestic shorthair cat was presented with a non-pruritic erythematous crusted nasal hypotrichosis along with bilateral ceruminous otitis externa. The cat was diagnosed with diabetes mellitus and was positive for feline immunodeficiency virus (FIV). Deep skin scraping, trichograms from lesional skin and ear canal parasitological examination were positive for Demodex cati. A 250 mg (55.5 mg/kg) fluralaner spot-on for medium-sized cats (Bravecto; MSD) was applied to the base of the cat’s head. Re-examinations were carried out on the fourth, sixth and eighth weeks after therapy. On the fourth week, the ceruminous otitis had resolved completely and the nasal lesions were markedly improved. One dead adult D cati was found in deep skin scrapings while other tests from the skin and both ear canals were negative. On the second re-examination only a mild hypotrichosis persisted on the nasal region and all parasitological examinations were negative. Eight weeks after the initial examination, the skin lesions had almost clinically resolved. On the 12th week, fluralaner spot-on was repeated. No recurrence was noted at the 6-month follow-up.

Relevance and novel information The use of isoxazolines has been reported for only a few demodectic cats but was described to be safe and effective. This is the first report to evaluate the efficacy of a single spot-on fluralaner for the treatment of localised dermatitis and otodemodicosis due to D cati, and suggests it as an effective, safe and practical treatment.