Prototheca zopfii Genotype 2-induced Nasal Dermatitis in a Cat

Few published cases of feline protothecosis exist; all of these were restricted to the skin and speciation of the causative organism revealed an infection with Prototheca wickerhamii in each case. This report describes Prototheca zopfii genotype 2-induced inflammation of the nasal skin and cutaneous mucosa of the right nostril in a 14-year-old neutered female domestic shorthair cat. Microscopical examination revealed marked pyogranulomatous inflammation with numerous intralesional algae. These had a round to ovoid shape, were 8-21 μm in diameter, formed endospores and displayed a positive immunoreaction for Prototheca zopfii antigen. By 18S rRNA gene amplification and sequencing the intralesional algae were confirmed as Prototheca zopfii and further characterized as Prototheca zopfii genotype 2. This case report reveals Prototheca zopfii as an additional Prototheca species associated with feline protothecosis.