What is it?
"Cat Flu" is a very common condition, causing sneezing, runny noses, sore eyes and similar "flu-like" symptoms in unprotected cats. It is also highly contagious, and easily spreads from cat to cat!
What causes it?
"Cat Flu" isn't actually a single disease - it can in fact be caused by four different disease organisms. The two most common are Feline Herpes Virus (FHV, also known as Feline Rhinotracheitis) and Feline Calicivirus (FCV). The third cause is less common, and is the Bordetella bacterium, the same as causes Kennel Cough in dogs. The final condition is Feline Chlamydia (Chlamydophila felis infection); unlike in most species, this bacterium does not usually cause intestinal upsets or reproductive disease, and rarely causes any symptoms except in combination with another infectious agent.
What cats are at risk?
Any cat can become infected! In general, young kittens, very old, or ill cats are at most risk of severe disease, however. The disease organisms are easily transmitted from cat to cat by droplets in the air (especially from sneezing), and some can remain viable and infective for a prolonged period. Many cats also become carriers for Feline Herpes Virus, as even after the symptoms have apparently resolved, the virus will still be dormant in their bodies (mainly in nerve ganglia). If the cat becomes ill or stressed in future, the virus will reactivate and may cause disease, or be shed to infect other cats. Chlamydia is most common in large colonies of cats, and in these situations, any of the organisms will spread like wildfire through the cat population.
What are the symptoms?
The main symptoms of Cat Flu are common to all four infections - runny nose, sneezing, lethargy, loss of appetite and a fever. In addition, Bordetella and Chlamydia often cause coughing; and both Herpes Virus and Chlamydia both cause sore, runny eyes and sometimes corneal ulcers. Calicivirus can lead to ulceration of the mouth and throat, and may result in severe systemic disease that can even be life-threatening.
How is it diagnosed?
In most cases, the clinical signs are diagnostic, and determining which organism is causing them isn't important. If for any reason it is important to distinguish between them, swabs from the eyes, nose and throat can be taken and sent away to a specialist lab who will grow the bacteria and isolate the viruses.
How can it be treated or managed?
There is no specific treatment for Herpes Virus or Calicivirus infection; however, antibiotics (against secondary infections and/or Bordetella and Chlamydia) are frequently prescribed, along with anti-inflammatory drugs (to reduce the fever and make the cat more comfortable). Sometimes, mucolytic drugs (to soften the mucus in their noses and help them to breathe) may be used as well. In severe infections, intensive care nursing, intravenous fluids and even interferon (to stimulate the immune system) may be needed. In most cases, however, good quality home nursing is more appropriate than hospitalisation. It is important to encourage ill cats to drink (for example, with running water, or by moistening their gums to stimulate thirst) and eat (with a bunged up nose, cats are often reluctant to eat because they can't smell the food - so strong-smelling foods such as fish, warmed, and hand fed, are often the best solution).
Can it be prevented?
Feline Herpes Virus and Calicivirus can both be prevented by vaccination, and are present in the normal annual boosters your cat should get. Although vaccination doesn't always stop the cat from carrying the viruses, it does mean that it is very unlikely for them to develop disease, or spread them. It is possible to vaccinate against Chlamydia, but this isn't normally necessary except in very large colonies of cats.