What causes a feline upper respiratory infection?
Feline upper respiratory infection (URI) is the common term for a respiratory infection caused by one or more viral or bacterial agents. Synonyms for this condition include feline infectious respiratory disease and feline upper respiratory disease complex (URD). The infection may be caused by one or more viral and bacterial agents capable of causing disease in cats. The most common viruses that cause upper respiratory infections in cats are feline herpesvirus type-1 (also known as feline viral rhinotracheitis or FVR) and feline calicivirus (FCV), while the most common bacteria that cause upper respiratory infections in cats are Bordetella bronchiseptica (B. bronchiseptica) and Chlamydophila felis (C. felis).
FVR and FCV are responsible for approximately 90% of all feline upper respiratory infections. More information about the most common infectious agents that cause an upper respiratory infection in cats can be found in separate handouts in this series of client education materials. Less common agents that may be involved in an upper respiratory infection in cats include mycoplasma or feline reovirus.
What are the symptoms of a feline upper respiratory infection?
The typical upper respiratory infection involves the nose and throat, causing symptoms such as sneezing, nasal congestion, conjunctivitis (inflammation of the membranes lining the eyelids), and discharge from the nose or eyes. Discharge may be clear or may become purulent (cloudy in appearance and containing pus). With FVR and FCV, the cat may develop ulcers in the mouth. Less specific symptoms of an upper respiratory infection include not eating, lethargy, fever, enlarged lymph nodes, and blepharospasm (squinting). In severe cases, the cat may have difficulty breathing.
How does a cat get an upper respiratory infection?
The viruses and bacteria that cause URI in cats are highly contagious. An infected cat will shed contagious particles in saliva or secretions from the nose or eyes. Susceptible cats can get an infection by direct contact with another infected cat or by environmental exposure to objects that have been contaminated with infectious secretions, such as food and water bowls, litter boxes, toys, and bedding. Most cases are associated with direct contact because the viruses and bacteria only survive for a short period of time in the environment and are readily destroyed by proper disinfection.
It is estimated that FVR can survive less than 18 hours outside the host’s body while FCV may live up to ten days. Dilute bleach solution will destroy both viruses but calicivirus will withstand washing with bleach-free laundry detergents.
Several of these diseases can cause a carrier state in cats that have apparently recovered from an infection, and female carriers can pass the infection on to their newborn kittens.
How long does a typical feline upper respiratory infection last?
Once a cat is exposed to an infectious agent, it will go through an incubation period of 2-10 days before developing clinical signs. If the infection is uncomplicated, it will typically last for 7-10 days, although signs may persist for up to 21 days in some cases. During this entire time, the cat may be infective to other cats.
With FVR, all cats become chronic carriers, meaning that they will have the disease for life. In some cats that carry FVR, stress (due to surgery, other illnesses, changes in the home, boarding, etc.) may cause the virus to become reactivated throughout life. With FCV about half of infected cats will become carriers of the disease. In some cases, the carrier state may only last for a few months. In a small percentage of cats, the carrier state may persist for life. These persistent carriers are usually asymptomatic but still serve as a constant source of FCV to susceptible cats.
How is a feline upper respiratory infection diagnosed?
Diagnosis of an upper respiratory infection is typically based on the characteristic clinical signs. Identification of the causative agent is not always necessary but will be recommended for breeding cats or if an individual cat responds poorly to treatment. If the disease is caused by a virus, the specific causative virus can usually be identified by collecting samples of cells and discharges from the nose, eyes or back of the throat. C. felis (bacteria) organisms may be identified via conjunctival scrapings (samples taken from an eye using a scalpel, usually with topical anesthetic and/or sedation). If the infection has spread to the lungs, samples may be collected for examination by a procedure called a transtracheal wash (passing sterile fluid through the lung).
If symptoms are long-lasting or recurring, additional diagnostic testing is warranted. This additional testing will usually include chest or skull x-rays, blood tests, or bacteria culture and sensitivity testing of abnormal discharge.
How is a feline upper respiratory infection treated?
Most cats with an uncomplicated upper respiratory infection can be treated symptomatically at home. Your veterinarian may prescribe an eye medication if your cat has a purulent eye discharge. Although viral infections do not respond to antibacterial drugs, broad-spectrum antibacterial drugs may be prescribed to prevent secondary bacterial infections from complicating the disease, particularly in kittens. Primary bacterial upper respiratory infections caused by Bordetella or Chlamydophila will be treated with specific antibiotics that are effective against these diseases.
"Most cats with an uncomplicated upper respiratory infection can be treated symptomatically at home."
Cats with nasal or airway congestion may benefit from increased environmental humidification, such as being taken into a steamy bathroom for 10-15 minutes several times per day. Some cats will benefit from nose drops if the nasal discharge is particularly severe or the nasal tissues become painful. To minimize irritation from nasal discharge, it is often helpful to wipe the cat's face or eyes with a moist tissue. Since cats with a respiratory infection will have a decreased sense of smell, they often have a decreased appetite. Feeding a highly palatable canned food may help improve their appetite. In some cases, an appetite stimulant may be prescribed.
If your cat is dehydrated, depressed, or has a severe case of illness, your veterinarian will recommend hospitalization for more intensive treatment, including fluid replacement therapy and other supportive treatments.
How can feline upper respiratory infections be prevented?
Since upper respiratory infections can be caused by a variety of different disease agents, it is not always possible to prevent them. However, there are standard core vaccines that provide protection against FVR and FCV. There is also a vaccine that protects against feline chlamydiosis (eye infection caused by the bacteria c. felis). This vaccine is considered non-core and will only be recommended if your cat has a reasonable risk of exposure to feline chlamydiosis. There is also a vaccine for a rare but especially serious form of calicivirus known as hemorrhagic calicivirus. Because there may be an increased risk of reaction to this particular vaccine, your veterinarian will discuss the risks and benefits of its use in your cat. None of these vaccines will completely prevent an infection from occurring if your cat is exposed to the disease, but they will significantly reduce the severity of the infection and shorten the length of the illness.
All of these vaccines require a booster on a regular basis. Your veterinarian will recommend a booster schedule for your individual cat, typically every one to three years depending on the vaccine and antigen.
Boarding facilities, humane societies, animal shelters, and cat shows are all places where susceptible cats can be readily exposed to these infectious diseases. Preventing direct contact between your cat and other cats will greatly minimize the chance that your cat will pick up an infection. Following good sanitation and hygiene practices, such as washing your hands thoroughly before and after petting another cat, will further reduce the likelihood of disease spread between cats.
Are other cats in the household at risk of infection?
A cat that has an acute upper respiratory infection will be infective to other cats during the incubation period and for up to three weeks after developing symptoms. A cat that is a carrier of an upper respiratory virus may always be infective to other cats (see question "How long does a typical feline upper respiratory infection last?"). Cats that are unvaccinated, are young or have chronic underlying conditions are more susceptible and may develop a serious illness. Adequately vaccinated adults will likely only develop a mild case of illness, which may resolve without treatment.
"A cat that has an acute upper respiratory infection will be infective to other cats..."
It is always prudent to isolate a new cat from the other cats in your household for at least 1-2 weeks to minimize the risk of transmission of any infectious diseases. During this time, the cat should be examined by a veterinarian to ensure it is safe for the cats to make contact.
Is my family at risk?
Most of the infectious diseases that cause upper respiratory infections in cats are very species-specific and do not represent any risk to people. Bordetella bronchiseptica can, in certain circumstances, cause illness in people with an immune system disease. There are isolated reports of people who live in the same household as an affected cat developing C. felis-associated conjunctivitis. Follow good hygiene practices to lessen the chance of infection, and if anyone in your household develops sore or runny eyes or signs of a respiratory infection while your cat is ill, it would be prudent to consult your physician. Fortunately, these zoonotic infections are extremely rare.