R.V. Barrs
Sydney School of Veterinary Science, University of Sydney, Camperdown, NSW, Australia
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
|
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 of 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 A. udagawae.
Because the fungi that cause aspergillosis are ubiquitous, and since C. neoformans has a 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 agglutination 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 immunodiffusion assays, are commercially available but have poor sensitivity.
- Oropharyngeal/conjunctival and nasal swabs. PCR testing or viral isolation for FHV-1 is usually unrewarding 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 cavity 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 Fr 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. Approximately 2–3 mL of sterile saline is flushed into the catheter and aspirated back. The collected sample can be used for aerobic and anaerobic culture, fungal culture, or PCR (e.g., for Mycoplasma or Bordetella).
- Endoscopic examinations are performed next with the anaesthetised cat in sternal recumbency. Avoid mouth gags that maximally open the mouth, as these occlude maxillary artery blood flow and can cause post-anaesthetic cortical blindness. Nasopharyngoscopy using a retroflexed bronchoscope or similar scope is performed to detect choanal mass lesions, stenotic lesions or foreign bodies. Mass lesions can be biopsied. Rigid antegrade rhinoscopy is performed next.
- Nasal lavage and nasal biopsy. Guided endoscopic or unguided nasal biopsies are collected for culture and histology. Therapeutic nasal lavage alleviates congestion in cats with CRS and is performed in the intubated cat (cuffed tube) with the pharynx packed with gauze. A 10-ml aliquot of sterile saline is flushed into the nasal cavity through one naris while the other naris is occluded with digital pressure. The procedure is repeated on the other side, and the gauze is then retrieved to inspect for foreign bodies, fungal plaques or tissue remnants. Nasal tumours, especially lymphomas, are friable and the nasal flush may yield tissue fragments for histopathology. Prior to extubating the cat, the pharynx should be suctioned carefully.
- Histology of nasal mucosal biopsies is essential to distinguish CRS from neoplasia and fungal infection. Inflammatory infiltrates in CRS can be neutrophilic, lymphoplasmacytic, eosinophilic or mixed and may be accompanied by epithelial erosions, turbinate lysis/remodelling, fibrosis, necrosis and glandular hyperplasia. Special stains to detect fungal hyphae such as PAS should be requested. If eosinophilic infiltrates are present and fungal stains are negative, immunohistochemistry for FHV may be performed.
Management of CRS
Treatment is palliative. Antibiotic therapy is guided by susceptibility results or given empirically for 6–8 weeks using clindamycin, doxycycline, amoxicillin-clavulanate or azithromycin. Longer-term or intermittent therapy may be required. Use of nasal decongestants should be limited to 3 days because rebound vasodilation can exacerbate signs. Famciclovir controls signs in some cats using 90 mg/kg q 12 h PO for 1 week beyond resolution of clinical signs.
Management of Nasal Cryptococcosis
Fluconazole is first-line therapy and is usually required for at least several months. Itraconazole is also effective but has more adverse effects (Table 2). In severe disease, combination therapy with amphotericin B and flucytosine is recommended for 4 weeks followed by azole monotherapy. Treatment is continued until the cryptococcal antigen latex assay titre is zero, with follow-up antigen testing 1 month after therapy has been stopped. The prognosis for resolution of infection is good (>75% successful), although relapses occur in 17% of cases.
Aspergillosis
Endoscopic removal of all visible fungal plaques combined with 1% topical clotrimazole infusion is recommended for SNA, and prognosis is generally favourable. For SOA the prognosis is generally poor, although individual cases have been cured. Posaconazole monotherapy or combined with terbinafine is recommended for first-line therapy, but treatment should be guided by the results of antifungal susceptibility testing (Table 2). Itraconazole should not be used empirically because resistance is common.
Table 2. Dosages of antifungals used in the treatment of fungal rhinitis
|
Drug
|
Dosage/Route of administration
|
Diseases
|
Adverse effects
|
|
Fluconazole
|
2.5–10 mg/kg q 12 h PO or 50 mg per cat q 12–24 h
|
C
|
• Inappetence
• Hepatotoxicity (rare)
|
|
Itraconazole
|
Capsules:
• 5 mg/kg q 12 h or 10 mg/kg q 24 h PO
• Administer with food
Oral suspension:
• 3 mg/kg q 24 h PO
|
C, A
|
• Anorexia, vomiting
• Hepatotoxicity: elevated liver enzymes, jaundice
|
|
Posaconazole
|
15 mg/kg PO loading dose, then 7.5 mg/kg q 24 h
Administer with food
|
C, A
|
Hepatotoxicity: infrequent compared to itraconazole
|
|
Voriconazole
|
12.5 mg per cat q 72 h PO
|
A
|
• Hypersalivation
• Blindness, ataxia, stupor
• Consider use when other therapies have failed
|
|
Terbinafine
|
30 mg/kg q 24 h PO
|
A
|
Anorexia, vomiting, diarrhea
|
|
Flucytosine
|
50 mg/kg q 8 h PO or 75 mg/kg q 12 h PO
|
|
Anorexia, vomiting, diarrhea
|
|
Amphotericin-B deoxycholate
|
0.5 mg/kg of 5 mg/ml stock solution in 300 ml per cat of 0.45% NaCl + 2.5% dextrose SC 2–3 times weekly to a cumulative dose of 10–15 mg/kg
|
C, A
|
• Nephrotoxicity: Monitor urea/creatinine
• Discontinue for 2–3 weeks if azotaemic
|
|
Liposomal amphotericin
|
1–1.5 mg/kg IV q 48 h
Give as a 1 mg/ml solution in 5% dextrose by IV infusion over 1–2 h
|
C, A
|
Nephrotoxicity: Monitor urea/creatinine every 2–3 days during administration
|
|
Caspofungin
|
Loading dose 1 mg/kg IV, then 0.75 mg/kg q 24 h IV
|
A
|
Uncommon
|
A, aspergillosis; ALP, alkaline phosphatase; ALT, alanine aminotransferase; C, cryptococcosis; PO, orally
Management of Nasal Neoplasia
Both radiation and chemotherapy have benefits in treating nasal lymphoma. B-cell lymphomas, the most common type of nasal lymphoma, respond well to radiation therapy and have the best prognosis. In one study of 97 cats with nasal lymphoma treated with radiation therapy (RT) alone, chemotherapy alone or RT + chemotherapy, the median survival time for all therapies was 473 days and was not significantly different for the different treatment modalities.
References
1. Johnson LR, Barrs VR. Rhinitis in cats. In: Bonagura JB, ed. Kirk’s Current Veterinary Therapy XV. Elsevier Saunders; 2015;Chpt 155:2014.