How I Treat the Chronic Feline Snuffler
World Small Animal Veterinary Association World Congress Proceedings, 2008
Margie Scherk, DVM, DABVP (Feline)
Vancouver, BC, Canada

Introduction

The chronic feline snuffler is a frustrating patient to treat. The longer it proceeds, the greater the consequences to affected tissues and the more debilitating it is. A diagnostic plan to differentiate probable etiologies and rule-out non-viral causes enables appropriate therapeutic choices. Even with viral etiology, therapies to reduce pathological consequences may help control clinical signs. Novel choices and drug combinations are discussed.

History and Presentation

Presentation includes sneezing, nasal discharge, and noisy breathing with or without inappetence. It can be useful to determine onset, duration and frequency of sneezing, whether nasal discharge changes throughout the day or season, and whether it is unilateral or bilateral.

The cat may sound hoarse or silent when meowing or the purr may change. Breathing may be 'worse at night', (reflecting bronchitis or merely the time that the client is at home to observe the cat) or worse after exercise or at rest, reflecting severity of disease or movement of secretions. Seasonal flare-ups suggest an allergic or irritant component.

Clients may notice facial asymmetry or ulcerations. Depigmentation may be attributable to chronic inflammation, infection or immune mediation. Ulceration of the nasal planum may be from concurrent herpes viral dermatitis. Caliciviral ulcers are typically located intraorally, on the lips or on the nasal planum.

Examination

Assess facial symmetry from in front and above. Palpate the face for swelling, invagination or discomfort. Thoroughly evaluate teeth and alveolar bone for periodontal disease, abscessation or inflammation. Evaluate the palate for oronasal fistula, masses or ulceration. Tonsils may be visualized. Open the mouth to evaluate neurologic competency: jaw tone (motor V), position, movements and symmetry of the tongue (XII), and gag reflex (IX, X).

Evaluate nasal passage patency using a cold small mirror/glass slide or wisps of cotton. Palpate the trachea to see if this elicits a cough. Auscult the trachea and thorax to define the primary location. Occasionally auscultation of the frontal sinuses using a small pediatric bell may be revealing. For pulmonary auscultation, use two heads, the standard bell and a Plexiglas scope (e.g., UltrascopeTM) as they provide different sensitivities and frequencies.

Perform a thorough physical examination, including fundic examination for Cryptococcus and signs of systemic disease. Regional and other lymph nodes should be assessed for enlargement. In older cats, a minimum database is critical as concurrent renal or other insufficiency will be compromised by dehydration/ inappetence.

Etiologies and Pathogenesis

Chronic rhinitis may be a sequel to acute rhinitis but may occur separately. It may represent an ineffective immune response to persistent viral infection. Feline herpesvirus 1 (FHV-1) may initiate turbinate resorption, allowing subsequent secondary bacterial infections, especially if conformation predisposes. Irreversible turbinate destruction may result in viral or inflammatory mediator-induced cytolysis.

Calicivirus infection results in a carrier state with continuous shedding for variable periods. Latency of FHV-1 accounts for recurrence of clinical signs during periods of stress; approximately 80% of infected cats are permanent carriers.

Primary bacterial agents include Bordetella bronchiseptica, commonly found as a commensal without causing morbidity. Mycoplasma spp. may be cultured, but are difficult to isolate. Chlamydophylliosis is uncommon; infection is limited to varying degrees of conjunctivitis. L-forms may be involved but require specific culture techniques for verification. Less frequently reported bacteria include Actinomyces spp., Haemophilus spp., and Capnocytophaga spp. Bartonella henselae is commonly detected by serology, but its role is not certain.

Bacteria are only part of the cause of the illness. When antimicrobial therapy of 7-10 day duration fails to result in resolution of disease, a thorough diagnostic work-up is recommended.

The main fungal organisms causing chronic upper respiratory disease are Cryptococcus neoformans vars. neoformans and gattii. These result in facial deformity and skin ulceration, usually with unilateral nasal discharge. Aspergillosis spp. and Penicillium spp. have also been isolated.

Trauma, conformational aspects, polyps, periodontal disease and foreign bodies all predispose to chronic infection. Chondritis and osteomyelitis often follow infection/inflammation and it has been suggested that chronic rhinitis/sinusitis may predispose to nasal lymphoma. Neoplasia further alters function and form, allowing secondary changes. Concurrent stressors or immunocompromise/suppression (e.g., retroviruses) increase the likelihood of refractive infectious agent involvement. Most nasal tumours occur in older cats and are malignant, tending to be locally invasive without metastasizing. Nasal tumours result in sneezing and unilateral nasal discharge; nasopharyngeal masses present with stertorous respiration. Further signs include variable facial deformity, epistaxis and epiphora.

Diagnostics

When rhinitis /rhinosinusitis is recurrent or chronic, a CBC, serum biochemistry, retroviral serology, urinalysis and blood pressure determination, are the minimum needed. If rhinoscopy is considered or if epistaxis has occurred, perform a coagulation panel. Any medications affecting hemostasis should be temporarily discontinued. If appropriate, perform fungal titres.

The next tier of diagnostics is critical. Skull radiography or CT/MRI to image dentition, nasal passages, sinuses and bone health require general anaesthesia. Conventional radiography underestimates the extent of disease. Probe all periodontal pockets, retract the soft palate to look for polyps and palpate the hard and soft palate. Three standard radiographic views should be exposed:

1.  Open mouth ventrodorsal view (for nasal cavity and bullae)

2.  Lateral view (for frontal sinuses--if a change is suspected, an oblique lateral view focusing on the sinus in question)

3.  Skyline view of the frontal sinuses (in dorsal recumbency opening the mouth wide to exclude the mandible)

Following imaging, samples should be harvested. Cytology of nasal passages does not appear to be reliable for detection of chronic inflammation and evaluation of chronic rhinitis. If lymph nodes are enlarged, cytologic specimens should be collected to use for staging in case neoplasia is diagnosed by histopathology.

The small size of cats makes rhinoscopy challenging: a flexible endoscope may be retroflexed around the soft palate if retraction using a dental mirror was unrevealing. To evaluate the more rostral portions of the nasal passage, a rigid 1.9 mm arthroscope with a 30 degree viewing angle may be used if a small flexible one is unavailable. Irrigation with sterile saline or Ringer's is essential for optimal visualization. Mucus exudation, polyp, mass, foreign body or webbing (nasopharyngeal stenosis) may be seen.

If disease is unilateral, evaluate the unaffected side first. Normal turbinate mucosa should be pale pink and smooth. Hyperemia, irregular turbinate surfaces and moderate discharge suggest pathology. Fungal plaques may be seen and biopsied. While adenocarcinoma and sarcoma appear as discrete masses, lymphoma may present as a mass or a diffuse infiltrate. In chronic disease, even if the mucosa looks normal, biopsies should be taken. The entire cavity should be examined before biopsying to avoid hindrance by bleeding. Afterwards, sedation and overnight hospitalisation may be desirable to facilitate hemostasis.

Samples should be collected for aerobic and anaerobic culture. Results must be interpreted with caution because n extensive normal flora occurs in the nasal cavity. Cultures from deep within the nasal cavity may improve diagnostic yield by avoiding superficial contamination. Calicivirus identification requires virus isolation (VI). VI may also be attempted for FHV-1, however exposure to FHV-1, Chlamydophyla and Mycoplasma may be determined using PCR. Sensitivity varies greatly between the PCR assays used and they may not distinguish between wild-type virus and vaccine virus. Before completion of anaesthesia, flush and aspirate the discharge to help the patient during and after recovery. The endotracheal tube must be well cuffed and the oropharynx packed with swabs to prevent aspiration.

Therapeutics

Specific Therapies

Practitioners frequently use antibiotics but do we know what organism is involved? If multiple organisms are cultured, the significance is questionable. Should a single species grow that is not a commensal, sensitivity results may be used. Therapy should be continued for 6-8 weeks without changing antibiotic if there is an initial positive response. Choose antibiotics that are safe for long term use, reach the site of infection at effective concentrations and penetrate cartilage and bone. Amoxicillin- clavulanic acid and chloramphenicol are reasonable choices. Clindamycin, doxycycline and chloramphenicol are also effective against Mycoplasma spp.; metronidazole and doxycycline modulate the immune response thereby reducing inflammation somewhat. Doxycycline is effective against Chlamydophyla and L-forms. Azithromycin (5-10 mg/kg PO q24h for 5 days, then q72h long term) has a long duration of action. Pulse or intermittent therapy predisposes to antibiotic resistance and cannot be recommended. Antibiotic ophthalmic drops may be administered topically directly to the nasal passage.

Should Cryptococcus spp. or Aspergillus spp. be cultured, specific antifungal protocols should be followed.

If an allergic component is suspected, , antihistamines may be considered e.g., chlorpheniramine maleate 1-2 mg/cat PO q12h. Less sedative antihistamines (e.g., fexofenadine, loratadine), selectively inhibit peripheral H1 receptors.

For FHV-1 infection, administration of the intranasal herpes and calicivirus vaccine two to three times a year may be beneficial in stimulating local immunity. L-lysine helps to reduce the frequency of herpesviral recrudescence by competing with arginine, preventing viral replication. The dose is 250 (kittens)--500 (adults) mg PO q12h long term. Interferon alpha has been recommended at 30 units PO q24h, or administered ophthalmically in saline for herpes virus keratitis or conjunctivitis. Cidofovir may be used as a 0.5% solution in methylcellulose ophthalmically q12h.

Polyps and foreign bodies should be removed. Nasopharyngeal stenosis/webbing requires surgical resection via a transpalatine approach. Like polyps, webs may reoccur. Dental disease should be treated repairing fistulae if present.

Surgical drainage and flushing may be warranted for some patients with chronic sinusitis. After openings are drilled into the frontal sinus, histopathologic samples and bacterial samples may be collected. Trypsin-containing solutions may help break up heavy mucus. Sinus ablation has also been described.

Feline nasal adenocarcinoma or undifferentiated carcinoma responds well to radiation therapy with or without preceding cytoreductive surgery. Generous excision of squamous cell carcinoma may be curative. Lymphoma responds to chemotherapy (COP protocol), but long-term control may be achieved with local irradiation.

Non-Specific Therapies

Maintaining hydration is essential for tissue perfusion, and to make secretions less viscous and easier to clear. Humidification of air is beneficial e.g., by steam, or instilling saline into the nostrils to stimulate sneezing and clearance of nasal passages.

Decongestants can be helpful: diphenhydramine HCl 2-4 mg/kg PO q8h, or dimenhydrinate 4 mg/cat PO q8h, or pseudoephedrine 1 mg/kg PO q8h. Nasal decongestant drops are challenging to administer, but can be very helpful: 0.05% xylometazoline (1 drop into each nostril SID for three days only to avoid rebound congestion).

Anti-inflammatories can reduce airway swelling, leading to improved breathing, less secretion and a more comfortable patient. Glucocorticoids may be used in lymphoplasmacytic rhinitis, the most common form of chronic rhinitis; these should be used intermittently rather than continuously long-term, e.g., prednisolone daily for a week, reducing to q48h over the next week. It is possible that glucocorticoids might result in recrudescence of the virus or virus shedding. Non-steroidal anti-inflammatories are alternative options e.g., piroxicam (0.3 mg/kg PO q48h) or leukotriene blockers (Zafirlukast: 0.5mg-1mg/kg q12-24h)

Nutrition is critical. In addition to cyproheptadine (1 mg PO q12h), mirtazapine at 3-4 mg/cat PO q72h is a newly recognized appetite stimulant for cats.

Acupuncture may be a useful adjunctive therapy.

Prognosis

Clients must understand that a cat with chronic rhinitis/rhinosinusitis will never be cured. With on-going management, the patient's quality of life can be improved with a reduction in sneezing and nasal discharge.

References

References are available upon request.

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Margie Scherk, DVM, DABVP (Feline)
Vancouver, British Columbia, Canada


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