Invasive mould infections of the naso-orbital region of cats: a case involving Aspergillus fumigatus and an aetiological review

Case and context This report describes a cat diagnosed with sinonasal-orbital Aspergillus fumigatus infection using advanced imaging, histopathology and culture. Aetiology, clinical aspects and treatment of this rare and devastating infection are discussed with reference to a literature review of invasive mould (ie, filamentous fungal) infections involving tissues of the naso-orbital region of cats. Presentations Invasive fungal infections can present with different localisations (nasal passages, sinuses, orbits, subcutaneous space, palate, etc) depending on the species involved and its means of introduction into the tissues. Localised subcutaneous lesions (swellings, ulcerations, masses, nodules, etc), without concomitant signs of nasal/orbital disease, generally result from traumatic injuries and subsequent inoculation of fungal spores into the subcutaneous space. In contrast, naso-ocular involvement and concurrent signs of nasal disease (nasal discharge, sneezing, masses protruding from the nostrils) generally result from inhalation of spores, with subsequent spread of infection into the nasal planum or penetration of overlying bone and invasion of the subcutaneous space. Aspergillus species typically show such an invasion mechanism and frequently affect orbital tissues. Dematiaceous fungi (ie, filamentous fungi with brown/black hyphae) are reported to cause solitary, less invasive, slowly developing lesions, probably as a result of traumatic injuries with inoculation of fungal propagules. Accordingly, the subcutaneous space is more frequently primarily involved. Treatment and outcome Whatever the mould species, reported treatment options include surgery and a series of antifungal drugs. The outcome is frequently poor, especially for Aspergillus infections, although various measures can be taken to maximise the chances of success, as discussed in this report.