What is the upper respiratory tract?
The upper respiratory tract includes the nose, throat (pharynx and larynx), and trachea (windpipe). The surface of the respiratory tract is lined with a mucous membrane, a layer containing specialized cells that secrete a protective mucus coating onto the tissue surface. The eyes and inner surfaces of the eyelids are covered by conjunctiva, a membranous tissue similar to the respiratory mucous membranes (for more information, see the handout "Conjunctivitis in Cats"). Tears drain from the eyes through a lacrimal duct, which drains into the back of the nose and throat. Because of this anatomical connection, the conjunctivae are often grouped as part of the upper respiratory tract and may be affected by upper respiratory disease.
What are the signs of a chronic upper respiratory infection?
When clinical signs of upper respiratory tract inflammation, such as sneezing or nasal and eye discharge, persist over weeks or months or when they tend to recur at intervals of a few weeks, the condition is referred to as chronic upper respiratory tract disease.
A runny or stuffed-up nose is the most common clinical sign in cats with chronic upper respiratory infections. The nasal discharge tends to be thick and often yellow. It may also be red-tinged (fresh blood) or brown (older blood). One or both nostrils may be involved. Because smell is essential to appetite, many affected cats have a poor appetite and lose weight.
"Because smell is essential to appetite, many affected cats have a poor appetite and lose weight."
There may also be inflammation in the throat that makes swallowing uncomfortable. This may lead to drooling in some cats.
Affected cats may have a chronic discharge from one or both eyes. In severe cases, facial swelling and resentment of handling or touching the face may occur due to pain or soreness. In other cases, these chronic signs are relatively mild, such as episodes of sneezing accompanied by a clear nasal or ocular (eye) discharge. Cats with mild symptoms usually retain a normal appetite. These milder cases may cause more distress to the owner (due to the constant sneezing or runny nose and eyes) than to the cat.
What are some of the leading causes of chronic upper respiratory tract disease?
There are many causes of this relatively common problem in cats. Feline viral rhinotracheitis (feline herpesvirus) and calicivirus were the primary causes of chronic upper respiratory tract disease before the development of vaccines in the 1970s. These viral infections caused severe mucous membrane damage in some cats; healing was incomplete, leaving the membranes susceptible to secondary bacterial infection (see handouts "Feline Herpesvirus Infection or Feline Viral Rhinotracheitis" and "Feline Calicivirus Infection" for more information).
These upper respiratory viruses persist in some cats, known as carrier cats, for weeks, months, or even years. In some, but not all, of these carriers, the chronic viral infection damages the protective mucous membranes and allows bacteria to invade the damaged tissues, causing persistent clinical signs. Vaccinated cats that have not been given the appropriate booster vaccines (especially against feline herpesvirus) or have been exposed to virulent strains of herpesvirus may still become infected with one or more of these viruses and later in life exhibit chronic post-viral rhinitis and conjunctivitis.
Chlamydophila felis and Bordetella are bacteria that can cause primary respiratory infections in cats. A group of organisms called Mycoplasma can cause primary respiratory and eye infections or play a secondary role, along with bacteria such as Pasteurella, Streptococci, Staphylococci, and many others. There is no feline vaccine for these organisms except for C. Felis and Bordetella. The immunity from the C. felis vaccine is relatively short-lived, and boosters are required annually (see handout "Chlamydial Conjunctivitis in Cats"). Vaccination against C. Felis and Bordetella is recommended only in certain circumstances.
"Chronic upper respiratory tract disease is a relatively common problem in unvaccinated cats."
Chronic upper respiratory tract disease is a relatively common problem in unvaccinated cats. The most common form is termed chronic post-viral or idiopathic rhinitis. In this condition, a viral infection (e.g., caused by feline herpesvirus or feline calicivirus) causes the initial mucosal damage. Still, the chronic signs relate to secondary bacterial infection of the damaged nasal passages. This may lead to chronic osteomyelitis of the nasal turbinate bones, a bacterial infection of the delicate bones within the nasal sinuses. This chronic inflammation can cause distortion or destruction of these structures.
What about other causes?
Some fungal infections can cause chronic upper respiratory tract disease; these infections are more likely in specific geographic regions. Cancer (neoplasia) affecting the upper respiratory tract is rare but may need to be ruled out in some instances (see handout "Nasal Tumors" for more information). In a few cats, non-cancerous nasal polyps may cause chronic sneezing and discharge. Occasionally, your veterinarian must rule out other causes such as trauma, foreign bodies trapped in the nose, or even dental disease.
How is the cause diagnosed?
To determine the extent and nature of the disease, it is essential to get an accurate history. Any past respiratory or eye infections, previous trauma such as an accident or fight, or dental disease should be reported. Details such as the onset and progression of the problem and the color and consistency of the discharges are essential. A thorough physical examination may also require blood work, swab samples for laboratory microscope examination and culture, radiographs, and tissue biopsy. Culturing the discharge may reveal a variety of bacteria, but these are often secondary invaders. Anesthesia may be necessary for a thorough nasal examination or to acquire specific diagnostic samples.
How can this problem be treated?
The test results and diagnosis will determine the treatment. In many cases, no specific initiating cause can be found. Antibiotics typically give an initial dramatic improvement that is often short-lived. Targeted nutritional supplements that promote a strong immune system can be helpful, especially in chronic viral infections. Anti-viral and immune-stimulating medications may be beneficial in some cases. Despite our best efforts, some cases remain chronic or at least recurrent. The treatment goal in these cases is to reduce the cat's discomfort through periodic medication and improve its quality of life.