Feline sino-nasal and sino-orbital aspergillosis. This thesis characterizes upper respiratory tract aspergillosis (URTA) in domestic cats, an emerging mycosis caused by fungi from Genus Aspergillus. Affected cats were 1.5 to13 years old (median 5 y). Brachycephalic purebred cats were over-represented. Sino-orbital aspergillosis (SOA) was more common than sino-nasal aspergillosis (SNA). Fungal pathogens were cultured readily. Aspergillus fumigatus was the most common cause of SNA. In all cases of SOA, the fungal pathogen was an uncharacterised species within the Aspergillus viridinutans complex in Aspergillus section Fumigati. This pathogen, also isolated from a dog and a human with aspergillosis, was subsequently identified as a novel species, A. felis (neosartorya-morph), using a polyphasic taxonomic approach including comparative sequence analysis of the ITS, partial β-tubulin and calmodulin genes. A. felis is heterothallic with a functioning reproductive cycle, as confirmed by mating-type analysis, teleomorph induction and ascospore germination. It can be distinguished from A. viridinutans by growth at 45 °C and from A. fumigatus by lack of growth at 50 °C. Computed tomography was used to investigate pathogenesis of URTA. Findings support that the nasal cavity is the portal of entry for fungal spores in feline URTA and that extension to involve the orbit is via direct naso-orbital communication from bone lysis. Sera from cats with URTA, and two control groups were tested to detect Aspergillus-specific antibodies using an agar-gel double immunodiffusion (AGID) assay and an indirect IgG ELISA. The sensitivity (SE) of the AGID was 43% and specificity (SP) was 100%. At a cut-off value of 6 ELISA Units/mL the SE of the IgG ELISA was 95.2% and SP was 92 - 92.9%. Aspergillus-specific antibodies against A. fumigatus and four cryptic species (A. felis, A. thermomutatus, A. lentulus, A. udagawae) were detected. Detection of Aspergillus-specific antibodies by IgG ELISA has high SE and SP for diagnosis of feline URTA
