Study flags occult fungal disease in cats with orbital signs
Bottom line
Cats with orbital fungal disease may not show the nasal signs many clinicians expect, according to a new retrospective case series in Veterinary Pathology that reviewed 11 cats diagnosed between 1998 and 2024. The authors found all 11 cats were mesocephalic breeds, mostly domestic shorthairs, and all presented with orbital disease such as exophthalmos and exposure keratitis without documented upper respiratory signs. Histology most often identified Aspergillus species, though oomycetes and Mucorales were also seen, leading the authors to suggest that some apparently “isolated” orbital cases may actually reflect subclinical sinonasal infection with extension into the orbit. (lifescience.net)
Why it matters: For veterinary professionals, the report broadens the differential list for cats presenting with unilateral orbital swelling, exophthalmos, third eyelid elevation, or exposure keratitis, even when sneezing or nasal discharge are absent. That’s clinically relevant because advanced imaging can help define lesion extent, but tissue sampling is still needed to distinguish fungal disease from neoplasia or other orbital processes. The finding that mesocephalic cats may present differently than the brachycephalic cats classically associated with feline aspergillosis could push earlier referral, biopsy, and antifungal planning in cases that might otherwise be worked up first as tumors or sterile inflammation. (lifescience.net)
What to watch: Whether this series changes how ophthalmology, internal medicine, and diagnostic imaging teams approach orbital disease in cats, especially decisions around CT, biopsy, fungal testing, and earlier suspicion of occult sinonasal involvement. (vet.cornell.edu)
Key facts
- Study type
- Retrospective case series
- Journal
- Veterinary Pathology
- Cases
- 11 cats
- Study period
- 1998 to 2024
- Presentation
- Orbital disease without documented upper respiratory signs
- Breed type
- All cats were mesocephalic; 10 were domestic shorthairs and one was a domestic longhair
- Most common organism
- Aspergillus species, 8 of 11 cases
- Other organisms
- Oomycetes in two cases, and Mucorales in one case
- Publication date
- Published online October 12, 2026
A new Veterinary Pathology case series is challenging a familiar assumption about feline orbital mycosis: cats can present with clinically important orbital fungal disease even when they don’t have obvious sinonasal signs. In 11 cases identified through the Comparative Ocular Pathology Laboratory of Wisconsin from 1998 to 2024, every cat presented with orbital disease, and none had documented upper respiratory signs at presentation. The study was published online October 12, 2026. (lifescience.net)
That matters because feline aspergillosis has typically been framed as either sinonasal disease or sino-orbital disease, with brachycephalic cats often described as predisposed. Existing guidance from Cornell and broader feline fungal disease reviews emphasizes nasal cavity involvement, advanced imaging of the head, and the potential for orbital extension, especially with Aspergillus infections. This new report adds to that picture by focusing on cats whose disease looked orbital first, without the overt nasal component clinicians may expect. (vet.cornell.edu)
The details are notable. The 11 cats were all mesocephalic breeds, including 10 domestic shorthairs and one domestic longhair, with ages ranging from 1.5 to 17 years and a median age of 7 years. Histologically, the lesions were described as eosinophilic and granulomatous orbital cellulitis with central necrosis. Aspergillus species were the most common organisms identified morphologically, accounting for 8 of 11 cases, while two cases involved oomycetes and one involved Mucorales. Panfungal PCR confirmed Aspergillus in only three cases and often amplified suspected contaminants, which underscores the practical limits of molecular testing in some archived or mixed samples. (lifescience.net)
The authors also reviewed previously published feline orbital mycosis cases and reported a pattern: mesocephalic cats more often presented with orbital signs, while brachycephalic breeds more commonly showed concurrent sinonasal disease. Their interpretation is that these “primary orbital” cases may not be truly isolated orbital infections, but instead subclinical sinonasal infections that preferentially extend into the orbit, possibly because of skull conformation. That’s an inference from the case pattern rather than a proven mechanism, but it gives clinicians a more nuanced framework for cases that don’t fit the classic textbook presentation. (lifescience.net)
Broader expert guidance supports the study’s clinical message. Cornell notes that bulging of the eye, third eyelid elevation, blindness, and balance changes can signal sino-orbital aspergillosis, and that CT can define disease extent in the nasal cavity, sinuses, and orbit, but cannot by itself distinguish fungal infection from cancer without tissue sampling. Reviews of invasive fungal infections in cats likewise emphasize that diagnosis requires demonstration of tissue invasion, and that treatment is often prolonged, expensive, and vulnerable to relapse even when initial response is good. (vet.cornell.edu)
Why it matters: For general practitioners, emergency clinicians, ophthalmologists, and internists, this paper is a reminder not to let the absence of nasal discharge lower suspicion for fungal disease in a cat with orbital signs. In practice, these cases may overlap clinically with neoplasia, cellulitis, abscessation, or inflammatory orbital disease. Earlier consideration of fungal differentials could affect referral timing, imaging choices, biopsy planning, and conversations with pet parents about prognosis, cost, and the likelihood of long treatment courses. It may be especially useful in mesocephalic cats, where the phenotype described here appears easy to miss if clinicians are anchored to the brachycephalic, sinonasal-heavy presentation reported in older literature. (lifescience.net)
What to watch: The next question is whether larger multicenter studies or prospective imaging-pathology work can confirm the proposed link between skull conformation and occult sinonasal spread. In the nearer term, clinicians will be watching to see whether this report changes diagnostic algorithms for feline orbital disease, particularly around earlier CT or MRI, tissue biopsy, fungal culture or PCR, and empiric planning for systemic antifungal therapy in referral settings. (lifescience.net)