Chronic rhinitis (Proceedings)

I have always considered this to be one of the more frustrating clinical problems to deal with in feline patients for a number of reasons. Among the key frustrations is a lack of understanding about exactly what this condition represents (i.e. Is there really a causal relationship to some form of infection? is it immune-mediated? Allergic?...). Since it is a diagnosis of exclusion, there is also always a bit of doubt about whether or not I may have missed a primary nasal disease. Lastly, it is difficult to know exactly what the best treatment for any given individual cat will be, and even if we do find a protocol that works for the cat and client, it is very unlikely that we will achieve a "cure".

The goal of this talk is to try to review the available information about chronic rhinitis in cats, and to share my experience and thoughts about diagnosis and treatment, especially in comparison (and sometimes contrast) to what I hear or read from other internists.

What can we say about etiology or pathogenesis?

One key point to make is that in this talk I am making a distinction between chronic rhinitis and acute upper respiratory tract infection complex (URTI), at least in terms of clinical presentation and approach to case management. In most cases of acute URTI, there is a clear history of potential exposure to viral or bacterial pathogens, either via contact with other animals or with fomites. In contrast, many cats seem to develop clinical signs of chronic rhinitis without a similar history.

Nonetheless, it is certainly possible that the same respiratory pathogens which cause acute URTI may play a role in development of chronic rhinitis. If this is the case, feline herpesvirus type 1 (FHV-1) seems like the most likely candidate. Approximately 80% of cats infected with this virus will probably become chronic carriers (although many of these cats may be completely asymptomatic). If FHV-1 does have a role in the development of chronic rhinitis, it could be the result of damage to the nasal turbinates incurred during the more severe acute phase of infection or during reactivation of latent infections later in life, or immunosuppression or immunomodulation due to viral persistence. In either case, damage to the normal nasal tissues or modulation of normal immune responses could pave the way for secondary bacterial overgrowth or infection. However, with the high prevalence of FHV-1 in the feline population and the potential for latent infections, it is very difficult to demonstrate any specific causal relationship between the virus and the condition of chronic rhinitis.

Some authors and researchers have also proposed a more primary role for bacteria or by-products of bacterial infection. Again, however, the presence of a substantial bacterial population in the normal nose and the very common development of secondary overgrowth or infection make it very difficult to clarify what role, if any, bacterial might play in the initiation of this disease.

Lastly, there is a possibility that, disease is not related to any primary infectious agent. It is possible that the inflammation observed in these cases is a response to inhaled particulates that act as irritants, toxins, or allergens. I have had a number of cases in which substantial clinical improvement has been achieved simply by removing potential irritants/allergens from the environment. One of the most common offending agents is cigarette smoke, but there are certainly other potential environmental causes as well.

Clinical Presentation

Unfortunately, there is no unique or consistent clinical presentation for chronic rhinitis. Cats of any age can be affected with reports of initial onset ranging from 6 months to 20 years of age. The most common clinical signs include stertor, visible nasal discharge, sneezing, or upper respiratory cough/gag (i.e. post-nasal drip). The character of the nasal discharge is variable. When secondary bacterial infections are present, the discharge will typically appear mucopurulent, but in the absence of such infection, it can be serous, mucoid, mucopurulent, hemorrhagic or any combination of the above. Nasal discharge is more commonly bilateral, but there are some cases which present with unilateral discharge.

The presence of ocular signs of discharge, conjunctival hyperemia or inflammation, or dendritic ulcers would be supportive of a herpetic infection, but these are not actually very common in cases of chronic rhinitis.

Enlarged regional lymph nodes may occasionally be seen as a reaction to severe inflammation, but as this is fairly uncommon, I would always recommend at least performing an FNA of the node in these cases or pursuing further workup in these cases to make sure that a more significant disease (e.g. cryptococcosis, neoplasia...) is not being missed.

Similarly, I always carefully check for facial symmetry, complete airflow obstruction, and differential ocular retropulsion and recommend further diagnostic testing if any of these clinical abnormalities are identified.

Chronic rhinitis or rhinosinusitis should really be considered a diagnosis of exclusion. In almost any primary nasal or nasopharyngeal disease, nasal tissues in the area of the primary lesion tend to become inflamed and secondary bacterial overgrowth or infection is common leading to substantial overlap in clinical presentation. In some cases, it may be worth an antibiotic trial initially, but in general, I recommend a diagnostic evaluation whenever possible to help rule out other conditions that might be more treatable or more serious (e.g. neoplasia, cryptococcosis, foreign bodies, tooth root abscess nasopharyngeal polyp...). I feel it is especially important to rule out other diseases in cases in which initial therapeutic trials have failed or signs are progressive over several months.

Diagnostic testing

As mentioned earlier, chronic rhinitis is really a diagnosis of exclusion, and as such, it is impossible to make a definitive diagnosis. The closest we can get is to have representative imaging and histopathology. Obviously acquiring biopsies is an invasive process, however, and there are some less invasive tests that I typically perform first.

In most cases, I recommend performing a minimum data base (serum chemistry, CBC, and urinalysis) even though this is very unlikely to help make a specific diagnosis of any nasal disease. The reason to perform these tests is really to help make sure we are not overlooking a systemic illness or abnormality that might predispose the cat to nasal problems (e.g. severe neutropenia), that might be important prior to any anesthetic event (e.g. kidney disease), or that might change the therapeutic options (e.g. liver or kidney problems, diabetes...). Along with the MDB, I will check the cat's FeLV/FIV status (if not previously known). If there is a hemorrhagic component to the nasal discharge, I also typically recommend checking the cat's blood pressure +/- coagulation status. I also commonly check for Cryptococcus infection utilizing the serum latex agglutination test prior to moving to the more expensive/invasive part of the diagnostic plan.

I will often test for common respiratory pathogens utilizing one of the commercial laboratory's PCR panels. While a positive result for an agent like FHV-1 or Calicivirus does not necessarily prove causation, it is still interesting/important information and can inform the discussion about long-term prognosis.

If initial testing is normal or non-diagnostic, the next steps will involve anesthesia. The first thing I do at the time of induction (prior to any other diagnostic testing is a thorough oropharyngeal examination and dental probing. Depending upon these findings, dental radiographs or nasopharyngoscopy may be indicated. If the oropharyngeal examination is normal, however, then the next step would be imaging tests of some sort. CT or MRI imaging is ideal, but when these are not available, good quality skull radiographs or rhinoscopy may be helpful. No matter what the imaging tests show, they will be followed by nasal biopsies. Biopsy samples should be submitted for histopathology and for culture and sensitivity (aerobic and Mycoplasma, +/- anaerobic and fungal).

Significant inflammation in the absence of a specific inciting disease process provides the support for a diagnosis of chronic rhinitis. The inflammation can be variable in type including cases with a predominantly suppurative, lymphocytic/plasmacytic, or occasionally eosinophilic pattern, but at this time it is not known whether these different types of inflammation represent real differences in underlying disease process.

Treatment options

Before discussing the specific treatment options, I think it is important to emphasize that most cats with chronic rhinitis cannot be "cured". My goal with any therapeutic regiment is to minimize clinical signs and improve the quality of life for the cat as much as possible. Some cats will be practically normal with only small amounts of serous nasal discharge from time to time, but there are some cats that suffer frequent infections, or have significant persistent clinical signs.

Antibiotics

Because secondary bacterial overgrowth or infection is such a common finding in these cases, antibiotics are often prescribed. Ideally antibiotic therapy is based upon culture and sensitivity results. If reasonable based on those results, or when I have to pick an empiric antibiotic, I most commonly use doxycycline or azithromycin since they achieve good penetration into the nasal tissues, would be effective against Mycoplasma species in addition to general aerobes, and may have some beneficial effects beyond their antibiotic properties. Some authors recommend treatment of at least 3-6 weeks, to cover a true deep tissue infection. I find that most cases do require this for their first treatment, but for many of the subsequent periodic "flare-up" secondary infections, shorter treatment durations of about 2 weeks are often sufficient.

Anti-inflammatory medications

Although somewhat controversial, for me, glucocorticoids are a mainstay of therapy for most chronic rhinitis cases. There is not much good evidence for their use in these cases, and I generally attempt to treat any active secondary bacterial overgrowth/infection first. I typically start with oral prednisolone, but do consider switching to inhaled forms in some cases once the condition is under control. I have not found non-steroidal anti-inflammatory medications to be very useful in these cases, but other authors have reported some success with piroxicam. Obviously, steroids and NSAIDS should not be used simultaneously.

Other options

Some cats with persistent clinical signs related to tenacious mucoid discharge benefit from supportive care utilizing saline drops or nebulization to help loosen secretions or periodic nasal flushing or suctioning to help mechanically remove secretions. In cases where that is not enough, pediatric decongestants containing phenylephrine can be tried, but caution should be used to avoid high doses. Lysine supplementation has been suggested as a potential adjunctive therapy for cases where chronic FHV-1 infection has been diagnosed or is strongly suspected. There may also be individual cats that would benefit from antihistamine therapy, but I have not found this to be useful. Lastly, in cases where a true allergy is suspected, there may actually be a role for testing and hyposensitization therapy, but I have not had many cases where there was a good opportunity to try this.