Johnny D. Hoskins, DVM, PhD, DACVIM
Enrofloxacin or marbofloxacin may be useful, and use of azithromycin is becoming popular in cattery and breeder situations.
Q: How does one manage cats with diagnosed chronic rhinosinusitis?
A: Dr. Lynelle Johnson at the 2003 American College of Veterinary Internal Medicine Forum in Charlotte, N.C. gave a lecture on chronic feline rhinosinusitis. Some relevant points in this lecture are provided in this column.
Acute upper respiratory tract disease typically affects young kittens and is characterized by sneezing, fever, malaise and bilateral nasal and ocular discharge (serous, mucoid or purulent). In severe cases, dehydration, debilitation and death can occur. Most infections are believed to involve feline herpesvirus type 1 (FHV-1), feline calicivirus (FCV) and/or Chlamydia.
Historically, FHV-1 has been estimated to account for most cases, although calicivirus may be more prevalent in some cat populations. In addition to viral infection as a cause for upper respiratory tract disease in cats, Bordetella bronchiseptica is recognized as a primary respiratory pathogen.
Additionally, Mycoplasma species or respiratory flora can be isolated more often in cats with chronic feline rhinitis than in asymptomatic cats, suggesting that Mycoplasma species are involved in the generation of clinical signs.
Also, cats tend to demonstrate transient improvement with intermittent antibiotic therapy. Clinical response may wane over time and cats may or may not show response with subsequent treatment regimens. Therefore, the primary or secondary role of bacteria in clinical signs remains difficult to define for the individual cat.
The pathogenesis of chronic rhinitis is unknown, and it is uncertain whether acute rhinitis is related to the chronic case. It is possible that FHV-1 is an initiating pathogen in chronic rhinitis with affected cats undergoing chronic or recurrent bacterial colonization secondary to anatomic or physiologic alterations.
An exuberant inflammatory response to the presence of virus or bacteria might worsen disease. Alternatively, clinical signs might be related to permanent destruction of nasal structures following acute viral cytolysis during a bout of acute severe rhinitis. Finally, virus may chronically reactivate from the trigeminal ganglia into nasal tissues and cause cumulative cytolytic destruction of nasal epithelium and bony turbinates.
Although cats with chronic rhinosinusitis appear to be relatively similar clinically, the disease is likely heterogeneous among the population. Individual susceptibility to pathogens, to environmental conditions, or genetic characteristics of the inflammatory response might all play a role in the generation of clinical signs. Determining the relative importance of previous or current FHV-1 and/or bacterial infection and the interrelationship of viral and bacterial organisms in disease pathogenesis might lead to improved treatment recommendations for the cat.
Investigation into feline upper respiratory disease syndrome is hampered by the fact that specific diagnostic tests are often not performed in cats with acute upper respiratory disease and are usually performed very late in the course of disease in cats with chronic rhinosinusitis. This is partly due to the self-limiting nature of the acute disease and partly due to the poor specificity of most available tests for potential infectious organisms.
Virus isolation, immunofluorescent antibody assays and serum neutralizing and ELISA antibody titers have been used to evaluate exposure to, or presence of, FHV-1 in cats with and without upper respiratory tract disease, and the correlation between test result and disease state is low.
While a positive viral culture from a nasal swab or biopsy might support the role of active viral infection in feline rhinitis, it might also simply indicate viral shedding in a chronic carrier. With the advent of molecular techniques, tests have been developed that are better at detecting organisms; however, it is not possible to confirm that the organism found is responsible for clinical signs.
Cats of any age can be affected by chronic rhinosinusitis. Chronic rhinosinusitis is typically characterized by a recurrent history of chronic intermittent or progressive sneezing, stertor, and mucopurulent or hemorrhagic nasal discharge. Chronic upper respiratory tract disease generally occurs without evidence of systemic or ocular disease.
Older cats may develop anorexia due to loss of smell and this can exacerbate underlying clinical conditions such as renal disease or chronic GI disease. Nasal discharge may be unilateral or bilateral, and the list of differential diagnoses includes fungal infection (primarily cryptococcosis and aspergillosis), inhaled foreign body, nasopharyngeal polyp or stenosis, neoplasia (adenocarcinoma or lymphoma), and dental-related nasal disease.
In cats presenting with nasal discharge, it is important to assess nasal airflow to determine the patency of both nasal cavities and the nasopharynx. With idiopathic rhinosinusitis, physical examination findings are usually normal with the exception of the upper respiratory tract. The junction of the hard and soft palate is palpated to detect mass lesions, and the dental arcade is inspected for gingivitis, tooth root abscessation or oronasal fistula. Regional lymph nodes should be carefully assessed, and a fundic examination may be helpful if cryptococcosis is suspected.
In most cats with chronic nasal discharge, a diagnostic work-up is performed relatively late in the course of disease and attempts to control signs for a prolonged period of time have occurred. At some stage, it is important to recommend diagnostic testing to rule out treatable conditions and to establish the characteristics of the disease.
The diagnostic work-up includes general laboratory work and feline serology (FeLV/FIV testing) to assess systemic health, followed by general anesthesia for skull radiographs or computed tomography (CT), rhinoscopy with biopsy and dental examination. Foreign bodies or bony malformations are usually obvious on radiographs or CT, and involvement of frontal sinuses can be readily detected. Subtle changes in turbinate structures and distinction of soft tissue densities in the nasal cavity are more difficult to discern.
When using skull radiographs, the intra-oral radiographic view is most helpful because it provides visualization of both nasal cavities in sufficient detail. This view is best-achieved using dental radiographic film that is placed inside the mouth during the exposure. It can also be obtained by placing the corner of a small radiographic plate into the mouth for the exposure, or by placing the cat in dorsal recumbency, opening the mouth wide, and angling the radiographic beam into the maxillary region.
A frontal sinus radiographic view is difficult to obtain in a cat because the sinuses are so small, and disease in this region can be missed on radiographs. In the cat with rhinitis, imaging generally shows variable degrees of turbinate lysis and increased fluid density within the nasal cavity.
Sinuses are often involved in the disease process as are tympanic bullae. Disease is usually bilateral but some cases are remarkably unilateral. Overall, CT provides better evaluation of the entire upper respiratory tract than do radiography, and it can detect cribriform invasion, which is an important determinant of prognosis in animals with nasal neoplasia or fungal infection. Both radiographic and CT changes in cats with rhinitis can mimic those found with neoplasia indicating the need to proceed with visualization of the nasal cavity and biopsy.
The rostral nasal cavity and caudal nasopharynx should be as completely evaluated as possible in every cat with upper respiratory signs. Caudal rhinoscopy (of the nasopharynx) is performed initially, either with a flexible endoscope retroflexed around the soft palate or by use of a dental mirror inserted into the oropharynx while the soft palate is being retracted cranially.
Examination of this region may reveal mucus exudation, a foreign body or mass lesion, or nasopharyngeal stenosis, a fibrous scar across the nasopharyngeal region that restricts nasal air-flow.
If a mass lesion is detected in the caudal nasopharynx, a biopsy can be obtained using a flexible endoscope, although it is sometimes challenging to retroflex the endoscope and biopsy instrument into the small nasopharyngeal region of a cat. It is generally wise to examine and biopsy the rostral nasal cavity before attempting a biopsy of the caudal nasopharynx, so that bleeding does not obscure the nasal cavity. Rostral rhinoscopy can be achieved using either rigid arthroscopic equipment or a semiflexible endoscope.
Cats with rhinitis display variable degrees of hyperemic mucosa, moderate to large amounts of mucoid to purulent discharge, and irregular turbinate structures. Destructive rhinitis is evident as increased space between the turbinates and is typically an indicator of long-standing or severe inflammation.
If white, yellow or black plaque lesions are seen in conjunction with destruction of turbinates, the possibility of Aspergillus infection is considered. This can be confirmed by a biopsy of the plaque revealing septate hyphae. In contrast, the presence of a mass lesion protruding between the turbinates should give rise to suspicion for neoplasia or cryptococcosis as a cause for nasal signs. Nasal adenocarcinoma typically appears as a mass lesion, while nasal lymphoma may appear either as mass lesions or a generalized mucosal infiltrate. In some cats, lymphoma may be found only in the nasopharynx as either a mass lesions or as a diffuse mucosal infiltrate.
Cats with moderate and severe inflammation may also appear relatively normal on rhinoscopy indicating a need to perform biopsies in cats to assess the severity and type of inflammation. Biopsies may show primarily neutrophilic, lymphocytic or pleiocellular inflammation in cats with chronic nasal signs. Typically, nonspecific histopathologic lesions such as fibrosis, necrosis, turbinate remodeling and glandular hyperplasia are present in addition to inflammation.
Nasal biopsy specimens can be collected for bacterial culture and may be helpful in guiding antibiotic therapy for secondary bacterial rhinitis. PCR evaluation of nasal biopsy or flush samples for Mycoplasma species appears to correlate with isolation of the organism on culture, provides a result much more quickly than standard culture techniques, and can detect non-cultivable species of Mycoplasma.
During rhinoscopy, it is helpful to flush and aspirate as much mucus from the nasal cavity as possible. Any isotonic fluid solution can be used. If flushing is performed in a rostral to caudal manner, the cuff on the endotracheal tube should be fully inflated to a level that blocks fluid without inducing tracheal trauma, and the oropharynx should be gently packed with lap pads to avoid tracheal aspiration of fluid. It would be safer to place a Foley catheter in the caudal nasopharynx and flush fluid from in a caudal to rostral direction. Removal of secretions from the nasal cavity usually aids in temporary improvement in clinical signs.
Cats with acute or chronic rhinitis are usually treated with broad-spectrum antibiotics in an attempt to control secondary bacterial proliferation in the nasal cavity. Cats with acute disease generally improve rapidly, sometimes even before antibiotic therapy has time to be effective. Cats with chronic disease usually demonstrate an initial response to antibiotic therapy, and a positive response may be an indication to initiate chronic (six to eight weeks or longer) antibiotic treatment. Commonly used antibiotics include doxycycline, cephalexin, amoxicillin-clavulanic acid or clindamycin.
Enrofloxacin or marbofloxacin may be useful, and use of azithromycin is becoming popular in cattery and breeder situations because the pharmacokinetics allows twice weekly dosing. Intermittent or suppressive antibiotic therapy may be helpful in some instances, but resistance to antibacterial action occurs commonly.
Antiviral therapy is rarely employed in cats with chronic rhinosinusitis because of failure to achieve definitive documentation of viral involvement and concern about potential side effects of antiviral therapy.
Currently, it is safe to use lysine as an antiviral agent at 500 mg PO BID. This amino acid replaces arginine in viral proteins rendering them nonfunctional and reducing viral replication. Lysine therapy is generally safe to use in young or older animals with acute or chronic rhinitis.
Steroids may reduce mucus production, and treatment may improve the cat's attitude or appetite. An alternative to steroid therapy is the use of piroxicam. This agent is generally well tolerated by cats at a dosage of 0.3 mg/kg PO daily or every other day, and some cats experience alleviation in clinical signs.
Because this drug is supplied in 10 mg capsules, the appropriate dosage for a cat must be specially prepared by a compounding pharmacy. Side effects include anorexia, vomiting and diarrhea.
Occasionally, cats will tolerate local instillation of isotonic fluid solution drops in the nasal cavity. This stimulates a sneeze response and encourages evacuation of mucus. In some cases, intermittent flushing of the nasal cavity under anesthesia (with tracheal intubation) can be useful in controlling clinical signs. Individual cats may show improvement with antihistamines or systemic decongestants; however, these drugs should be used cautiously in cats. Topical decongestants are often recommended for alleviation of serous nasal discharge in acute rhinitis, but it seems unlikely that these are effective in the presence of purulent nasal discharge.
Owners should be informed that cats with chronic rhinosinusitis have a guarded prognosis. Clinical signs of sneezing and mucopurulent discharge are difficult to control and impossible to eradicate. Signs may abate somewhat with long-term antibiotic, anti-inflammatory and other adjunct therapies but signs of rhinosinusitis virtually always recur.
Surgical therapy can be offered when medical therapy fails to control signs to a reasonable extent. Frontal sinus ablation can be effective in controlling clinical signs. Sneezing and nasal discharge may not be totally obliterated with this technique; however, substantial improvement can be seen in some cases. This procedure may be associated with complications such as intraoperative hemorrhage and persistent anorexia due to loss of smell.
What's your question? Send your pediatric/geriatric related questions to: Pediatric/Geriatric Protocol, DVM Newsmagazine, 7500 Old Oak Blvd., Cleveland, OH 44130. Your questions will be answered by Dr. Hoskins in upcoming columns.