Feline chronic rhinosinusitis accounts for 35% of nasal disease cases

Feline chronic rhinosinusitis accounts for 35% of cases of feline nasal disease, according to a clinical review published in Today's Veterinary Practice by Drs. Fellman and Swartz at Cummings School of Veterinary Medicine at Tufts University.

The review states the condition is the second most common cause of feline nasal disease after neoplasia and causes significant morbidity and impact on quality of life. The authors describe it as "a source of frustration among general practitioners, internists, and cat owners" given "its chronic clinical course and lack of effective therapeutic options."

What the 35% figure measures and what it leaves out

The 35% prevalence figure comes from cases of feline nasal disease, not from the general cat population. The review does not state the denominator, whether that's referral cases, primary-care cases, or a mix, or the timeframe the figure covers.

The typical clinical picture, according to the authors, is "a cat of any age with chronic, intermittent nasal signs that are often transiently responsive to antimicrobial treatment." The review states that "disease onset is typically in young to middle-aged cats," though older cats can still develop the condition. The authors refer to these cats colloquially as snufflers.

The underlying etiology is uncertain. The authors suspect it results "from a combination of genetics, environmental exposures, and potentially prior infections," with the result being inflammation and excessive mucus production in the nasal passages. While the response to antibiotics suggests a bacterial component, the review states that primary bacterial rhinitis is considered rare. The authors write that the underlying inflammatory condition is instead thought to predispose to secondary infection with bacteria.

The diagnostic workup and where it stops

The review states that "diagnosis requires elimination of other differentials that cause upper respiratory signs." As part of an overall assessment, the authors recommend baseline CBC, serum biochemistry, and retrovirus testing, noting that "immunosuppression associated with retroviral infection may predispose to either neoplasia or upper respiratory tract infections."

According to the review, "PCR testing is available for the detection of common viruses and bacteria that can cause nasal signs," including feline herpesvirus type 1, feline calicivirus, Chlamydia felis, Bordetella bronchiseptica, and Mycoplasma species. The authors write that "interpretation can be difficult in the setting of chronic disease given the high prevalence of some of these infections (particularly FHV-1 and FCV) in healthy cat populations."

The review states that "swabbing nasal discharge for cytology is of limited value, with the inflammatory cell type present frequently discordant with histopathology findings." The authors write that "aspiration of visible mass lesions is recommended and can support diagnosing either fungal disease or neoplasia."

Computed tomography remains the preferred imaging modality, according to the authors. The review states that "head radiography requires general anesthesia due to the need for specific positioning and multiple views to limit superimposition and still provides less information than CT, which allows for more accurate evaluation of osseous and soft tissue structures."

According to the review, "both anterior and posterior rhinoscopy can be performed in cats." The authors write that "anterior rhinoscopy can be limited by small patient size but is feasible with appropriate equipment, including a 2- to 3-mm flexible endoscope or a rigid endoscope with a viewing angle of 0° to 30°." Normal nasal mucosa is pink and smooth. The review states that abnormalities associated with chronic rhinosinusitis "can include increased mucus, increased friability of tissue, ulceration, congestion, and hyperemia."

The authors recommend biopsying "bilaterally even if nasal tissue appears mildly affected or normal," writing that "rhinoscopic assessment of disease severity may not correlate with biopsy findings." According to the review, "biopsies are important to rule out nasal lymphoma, which may or may not cause a mass lesion on CT." The authors write that "inflammation is classified according to the cells present, with common types including lymphoplasmacytic, neutrophilic, eosinophilic, or mixed inflammation."

Bacterial culture value is questionable

The review states that "the value of bacterial culture from any nasal sample is questionable," because "it is difficult to determine whether identified organisms represent normal flora and the bacteria identified can vary depending on the sampling technique." The authors add that "treatment response may not correlate with bacterial culture results."

According to the review, "previous retrospective studies have isolated a variety of bacteria from the feline nose, including Pseudomonas species, Escherichia coli, Staphylococcus species, and Pasteurella multocida." One study the authors cite found cats with chronic rhinosinusitis "were more likely than healthy controls to have Mycoplasma species and anaerobes" identified. The review states that "potentially pathogenic bacteria were also identified more frequently in cats with" chronic rhinosinusitis compared to control cats, though "a causative role in disease could not be" assessed.

The authors write that "the nose is not a sterile environment, and normal bacterial flora are found in healthy cat noses." Some recommend performing bacterial cultures "from biopsy and/or nasal flush samples as opposed to nasal discharge," according to the review.

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Where this leaves the associate with a snuffler in the exam room

The 35% figure is the headline number, but the clinical takeaway is the review's statement that bacterial culture value is questionable and that treatment response may not correlate with bacterial culture results. That gives an associate a defensible position when a client calls for the third time this year about nasal discharge. The culture may not tell you what to treat, and treating what it grows may not resolve the signs.

The diagnostic workup the review describes is thorough: CT, rhinoscopy, bilateral biopsies even when tissue looks normal. The framing as a diagnosis of exclusion and the statement that bacterial culture value is questionable both suggest that ruling out neoplasia and fungal disease are the critical gates, not chasing a bacterial isolate. The review does not give a treatment protocol, but the description of chronic, intermittent signs that are transiently responsive to antimicrobial treatment tells you this is a condition where setting expectations on the first visit matters more than the antibiotic choice.

We'd frame the conversation around a chronic course, not a cure. The review gives you the language to explain why repeated cultures may not change the outcome and why the workup is about ruling out the things you can treat definitively, lymphoma, fungal disease, a polyp, rather than finding the right antibiotic for the bacteria that may just be normal flora in an inflamed nose.

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