Sneezing Cats and Sinus Clues: UK Study Reveals Scope and Struggles of Feline Fungal Rhinosinusitis

Fungal Rhinosinusitis in Cats in the United Kingdom: 34 Cases (2013–2022)

Oliver Luke Russell et al

Background
Feline fungal rhinosinusitis (FRS) is a rare and under-characterized condition in the United Kingdom, typically caused by Aspergillus spp. or Cryptococcus spp. Diagnosis is challenging due to the need for advanced imaging and invasive diagnostics. Treatment and prognostic expectations vary widely, and few large-scale studies have addressed its presentation, diagnosis, and outcomes in cats. This multicenter retrospective study aimed to detail the clinical and diagnostic features, treatment approaches, and outcomes of cats with confirmed FRS in the UK.

Methods
A retrospective review was conducted across 10 UK veterinary referral hospitals. Medical records from 2013–2022 were searched for cats diagnosed with FRS based on clinical signs, advanced imaging (CT/MRI), visualization of fungal plaques, histopathology, fungal culture, or panfungal PCR. Data on presenting signs, diagnostics, fungal speciation, treatments (debridement, topical, systemic antifungals), and outcomes were collected and analyzed using descriptive and comparative statistics.

Results
Thirty-four cats met inclusion criteria, with a median age of 10.8 years. Sneezing (79%) and nasal discharge (62%) were the most common presenting signs. Turbinate lysis was noted in 79% of cases, predominantly affecting the caudal nasal cavity, and 47% exhibited lysis of adjacent bony structures. Fungal plaques were visualized in 60% of rhinoscopic exams. Histopathology confirmed fungal hyphae in 91% of cases, though fungal culture and panfungal PCR showed inconsistent agreement. Aspergillus fumigatus was the most commonly identified species.

Initial treatment included systemic antifungals in 77%, topical antifungals in 32%, and debridement in 53%, often in combination. Clinical remission (CR) was achieved in 50% of cases, but relapse occurred in 41% of those initially responding. Long-term (>90 day) remission was confirmed in only 38% of cats. Outcomes for confirmed Aspergillus cases (17/34) were similar, with 47% achieving CR at final follow-up. Side effects were uncommon but included hepatotoxicity, vomiting, and mild nasal irritation.

Limitations
Limitations included retrospective design, non-standardized diagnostic and treatment protocols, inconsistent follow-up, and potential underreporting of adverse effects or relapses. Variability in fungal identification methods and lack of consistent fungal speciation reduced diagnostic precision. Imaging reports, rather than scans, were relied upon for characterizing disease extent.

Conclusions
Fungal rhinosinusitis in cats presents with nonspecific nasal signs but often involves significant turbinate and bony destruction, warranting suspicion in chronic or recurrent rhinitis. Diagnosis frequently requires multimodal testing. Treatment is variably effective, and prognosis is guarded, with many cats experiencing relapse or persistent disease despite aggressive intervention. Early, multifaceted diagnosis and targeted antifungal therapy, ideally guided by speciation, are essential for improving outcomes.

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