Feline Sporothrix spp. detection using cell blocks from brushings and fine‐needle aspirates: Performance and comparisons with culture and histopathology

Background Sporotrichosis is an emerging zoonotic mycosis that presents as a cutaneous lymphatic or disseminated disease, caused by fungi from the Sporothrix schenkii ( S schenkii ) clinical clade. Its importance is growing, primarily due to an outbreak that occurred in Brazil, affecting mainly cats and people. Objectives In Brazil, an S schenkii diagnosis is often made using cultures, which allows genus identification and sufficient growth to perform molecular biology testing. Despite its advantages, fungal cultures are slow to develop and can delay public health measures, highlighting the importance of developing additional diagnostics techniques. Methods Cell block cytology (CBLC) is an older method that regained importance after liquid‐based cytology (LBC) was introduced, and it has been previously and successfully applied to veterinary diagnostics. We aimed to standardize and compare CBLC from cervical brush exfoliation of open wounds and fine‐needle aspirates with culture and immunohistochemistry of skin biopsies for sporotrichosis in cats, as a novel method. Results For this purpose, we selected 40 cats with skin lesions suspected of having sporotrichosis in Guarulhos city, São Paulo state, Brazil. We achieved 97.5% and 95% positivity using CBLC and culture, respectively, and 100% of feline skin biopsies were positive for Sporothrix spp on histopathology/immunohistochemistry. Conclusions Cell block cytology is an efficient and rapid tool to diagnose sporotrichosis in cats, particularly during epidemics.