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WSV18-0211
SVA FELINE
CURRENT APPROACH AND MANAGEMENT OF DISEASES OF THE NASAL CAVITY IN CATS
R.V. Barrs1
1Sydney School of Veterinary Science, The University of Sydney, NSW 2006
Introduction
Presentation for chronic nasal discharge and sneezing is common in cats of all ages. Chronic rhinosinusitis (CRS) is the most common cause of this presentation in clinical practice. Diagnosis requires exclusion of other causes of nasal discharge and sneezing (Table 1):
Table 1: Causes of nasal cavity disease in cats
Your Singapore, the Tropical Garden City
worldwide distribution and C. gattii is endemic
in many regions of the world cryptococcosis and aspergillosis should be considered in any cat with chronic URT signs.
Diagnosis
Findings at presentation can help rank differential diagnoses, but clinical signs overlap with infectious, inflammatory and neoplastic causes. Exophthalmos is a common sign in cats with fungal or neoplastic lesions invading from the nasal cavity into the orbit. A mass in the orbit causes loss of retropulsion
of the globe, prolapse and inflammation of the nictitating membrane, conjunctival discharge and central corneal ulceration. Orbital masses often invade into the oral cavity, detected
as a submucosal or ulcerated mass in the pterygopalatine fossa adjacent the most caudal molar tooth. Seizures and other CNS signs occur in neoplasia and fungal infection due to extension of disease.
Investigation
· Serology. Detection of cryptococcal antigen in the blood using a latex cryptococcal antigen aggluti- nation or cryptococcal antigen lateral flow assay
has high sensitivity and specificity for diagnosis of cryptococcosis. Detection of Aspergillus-specific
IgG has high sensitivity and specificity for diagnosis of aspergillosis, but commercial assays are lacking. Assays to detect precipitins, such as agar immunodif- fusion assays, are commercially available but have poor sensitivity.
· Oropharyngeal/conjunctival and nasal swabs – PCR testing or viral isolation for FHV-1 is usually unreward- ing in cats with CRS since viral shedding has ceased; Bacterial culture of superficial nasal swabs is equally unrewarding since commensals will be cultured.
· Dental probing to identify deep periodontal pockets, oronasal fistulae or palatine defects is performed along with imaging, rhinoscopy and biopsy under general anaesthesia.
· Diagnostic imaging – CT is superior to radiography for evaluation of nasal cavity and paranasal sinuses. Images should be evaluated for evidence of tooth- root infection. Imaging features of CRS, neoplasia and fungal rhinitis overlap including severe turbinate lysis and soft-tissue attenuation within the nasal cav- ity and sinuses. Obstruction of the Eustachian tubes, common with neoplasia and inflammatory disease, results in opacification of the tympanic bullae.
· Diagnostic nasal lavage – is performed to collect diagnostic material for bacterial culture for cases of CRS, although results may represent normal flora. A 6 to 8 F sterile catheter is inserted into the nasal cavity, ending rostral to the medial canthus of the eye. The nasopharynx is occluded using digital dorsal pressure on the soft palate. Approx. 2 - 3 mL of sterile saline is flushed into the catheter and aspirated back. The collected sample can be used
   Inflammatory and Infectious Causes
· Chronic rhinosinusitis
· Nasopharyngeal or nasal polyps
· Nasopharyngeal stenosis
· Dental disease – secondary bacterial tooth root infections · Foreign bodies
· Fungal rhinitis – cryptococcosis, aspergillosis
 Neoplastic Causes
· Lymphoma
· Adenocarcinoma
· Squamous cell carcinoma · Undifferentiated carcinoma · Fibrosarcoma
· Osteosarcoma
 Chronic rhinosinusitis (CRS)
Cats with CRS typically present with a history of
> 4 weeks mucopurulent nasal discharge and sneezing. Feline herpes virus-1 (FHV) is thought to have an initiating role, resulting in severe mucosal damage and turbinate lysis, compounded by an exuberant immune-response, possible cycles of FHV reactivation and recurrent secondary bacterial infection.
Fungal rhinosinusitis
Aspergillosis occurs in two forms; sino-nasal aspergillosis (SNA) and sino-orbital aspergillosis (SOA). Both infections arise in the nasal cavity after inhalation of fungal spores (conidia). In SOA, which is more common (65% cases), infection spreads to involve the orbit and paranasal tissues. Brachycephalic breeds, especially Persians and Himalayans are predisposed to SNA and SOA (40% of cases). SNA is most commonly caused
by A. fumigatus and A. niger, while SOA is most commonly caused by A. felis and by A. udagawae.
Because the fungi that cause aspergillosis are ubiquitous, and since C. neoformans has a
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