Chronic Upper Respiratory Disease in Cats: Why is a Clinical Cure so Challenging?
- Chronic relapsing or recurring rhinitis is a common presenting complaint in cats.
- Most cats presented with refractory rhinitis have increasingly resistant microbial infections secondary to previous turbinate damage due to feline herpesvirus-1.
- The bacterial flora shifts over time in cats with chronic bacterial rhinitis and as a result of chronic antimicrobial therapy or corticosteroid treatment.
- Clinical signs suggestive of neoplastic disease or fungal infection include epistaxis, epiphora, asymmetric lesions, facial and/or oral deformities, fundic lesions (fungal disease), and pain.
- Bacterial (and less commonly fungal) infections of the nasal cavity may ascend into the frontal sinuses or middle ear cavities.
- It is impossible to determine if a cat has frontal sinusitis based on historical and clinical sign CT scans are required to confirm the diagnosis.
- Surgical therapy may be required in some complications of nasal disease to complement medical therapies; for example, surgical drainage with frontal sinus or middle ear disease, or debulking in neoplastic or cryptococcal disease.
EVALUATION OF THE CAT WITH NASAL DISEASE
The complexity of the diagnostic evaluation will depend on the chronicity of the clinical signs, age of the patient, financial resources of the owner, previous treatments and responses, and whether atypical signs are pres Diagnostic tests beyond a meticulous physical examination may include:
- Otoscopic examination.
- Dental examination.
- FeLV and FIV testing.
- Cytological examination of nasal discharges (usually low-yield).
- Cryptococcus latex serum agglutination te
- Ocular fundic examination.
- CT scan of nasal cavity, frontal sinuses, and osseous bu
- Retroflex fiberoptic endoscopic examination of nasopharynx with aerobic and anaerobic bacterial and mycoplasma cultures of choanal exudates, and brush cytologi
- Rostral rhinoscopy with turbinate mucosal/bone pinch biopsies for aerobic and anaerobic bacterial and fungal cultures, and histopathologic examination.
- PCR testing for respiratory pathog
BACTERIAL RHINITIS OR RHINOSINUSITIS
- With very few exceptions (for example, Bordetella bronchiseptica), bacterial infections of the upper respiratory tract are opportunistic sequelae to other primary causes of rhinitis.
- Viral diseases, especially FHV-1 infection, are the most common predisposing cau FHV-1 causes necrosis of the turbinate mucosa, and possibly the turbinate bones, thereby altering the surface physiology of the mucous membranes and allowing colonization by potentially pathogenic bacteria.
- Following acute viral infection, early bacterial opportunists include commensal bacteria already residing in the upper respiratory tract; for example, Staphylococcus sp, Streptococcus sp, and Pasteurella multocida. Initial antimicrobial treatment should be directed at these bacterial organism
- With time, and after multiple treatments with antimicrobials, other opportunists (Mycoplasma sp) or more resistant organisms (Pseudomonas aeruginosa) start to colonize the nasal mucos Ultimately, many affected cats end up with pure cultures of P. aeruginosa in their posterior nasal cavities and connected anatomical sites.
- Occasionally, FHV-1 infection may cause chronic mucoid rhinitis and turbinate mucosal congestion without obvious secondary bacterial infection
B. Clinical signs
- Affected cats usually are presented for chronic sneezing, with mucoid to mucopurulent nasal discharg In most cases, discharges are bilateral and usually symmetrical. Feline nasal discharges are often thick and tenacious due to their high sialic acid content. Cats, therefore, often have difficulty expelling nasal exudates effectively. Epistaxis is rare, and facial deformity is not present. Concurrent ocular discharges may be present in some patients, especially if previous FHV-1 conjunctivitis has occurred. The nasolacrimal ducts may be obstructed by scarring, causing epiphora.
C. Concurrent frontal sinusitis
- About two-thirds of chronically affected cats develop ascending infections into one of both frontal sinuses
- Cats with concurrent sinusitis have clinical signs indistinguishable from those who have rhinitis alone
- CT scans are necessary to document the presence of frontal sinusitis. The sensitivity of skull radiographs is low.
D. Concurrent otitis media
- Effusions occur in the middle ear cavity in about one third of cats with chronic rhin Not all effusions are associated with ascending infections.
- Middle ear effusions may be an incidental finding on CT scans, or may be associated with clinical signs of head tilt, snuffling and gagging (as exudates drain into the pharynx under pressure), or deafness (when bilateral).
- History of acute viral infection, followed by chronic history of nasal discharge
- Exclusion of other diagnoses with similar clinical signs, but with other distinguishing features (epistaxis, facial deformity, etc.).
- Exclusion of FeLV or FIV infections as predisposing cau
- Response to appropriate antimicrobial treatment, with or without relapse.
- Advanced diagnostic testing
- Thorough deep otoscopic examination.
- Thoracic radiographs to exclude concurrent lower airway disease.
- CT scan of nasal cavity, sinuses, and osseous bullae.
- Retroflex endoscopy of the posterior nasal cavity, with brushings for cytological examination, and for aerobic and anaerobic bacterial and mycoplasmal cul
- Rostral rhinoscopy with cultures and histopathological examination of pinch biopsies of turbinate mucosa (and bone). Fungal cultures may be performed if suspicious lesions are observed.
- Oral antimicrobial therapy. Choice of drug and duration of treatment will depend on stage of disease, chronicity of signs, and response to earlier treatment Amoxicillin, amoxicillin-clavulanic acid, doxycycline, pradofloxacin or a first-generation cephalosporin are suitable for acute infections. Newer generation quinolones, such as marbofloxacin, may be needed for chronic resistant infections. Doxycycline, pradofloxacin, or azithromycin are indicated for mycoplasmal infections.
- Warm moist air humidification to liquify thick nasal discharg 0.125% phenylephrine nasal drops (Little Noses™) may help to decrease turbinate mucosa edema (one drop in each nostril q12h for 3 days, then stop for 3 days, and then repeat cycle as necessary).
- Frontal sinus trephination, or myringotomy or ventral bulla osteotomy (with antibiotic treatment based on culture), for patients with sinusitis or bacterial otitis media respectively. Neither of these conditions may resolve with antimicrobial treatment alone.
- Concurrent otitis media may not be infectious in all ca Swelling of the Eustachian tube may impair drainage of normal middle-ear secretions in some patients.
- Depends on duration and willingness of owner to pursue imaging and culture
- Patients treated symptomatically often have lifelong relapsing clinical signs
John R. August, BVetMed, MS, MRCVS, Dip ACVIM Dean of Faculties and Associate Provost
Texas A&M University