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.