Select Page


Contagious Feline Diseases

Contagious Feline Diseases

There are several viral infections that are important for cat owners to be familiar with. We have vaccinations for some of them. Your cat’s risk for these will depend on lifestyle and origin. Barn cats and strays have much higher risk for feline leukemia (FeLV) and the feline immunodeficiency virus (FIV). Purebred cats have higher risk for feline infectious peritonitis (FIP). All cats have risk for Herpesvirus.


Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV) are retroviruses, similar to HIV/AIDS in humans. Risk is highest for outdoor cats.

Infected cats will usually not show symptoms for several years but eventually will develop infections or cancer related to the virus. Average life expectancy for cats with FeLV or FIV is around 7 or 8 years.

Infected cats are contagious even without symptoms. Infection is primarily spread from cat to cat by fighting, mating or from mother to kittens. Although they are not spread from cat to cat by sharing bowls or litter boxes, if one cat in a household has one of these viruses, other cats in the household are still at risk, especially if they are young, old or immune-compromised.

Infected cats have compromised immune systems. They are vulnerable to other infections and may be anemic as well. Having one of these viruses will affect all your future health care decisions. Therefore, all cats should be tested for these viruses when they are young.

What does testing entail?

This is a blood test requiring just a couple of drops of blood. The test only takes about 20 minutes to run. We test all kittens and newly adopted adult cats who have not already been tested. Some humane societies do the testing before they adopt cats out but others do not. Cat breeders will usually have tested parent cats before selling the kittens – check for that if you are purchasing a purebred cat.

Kittens must be at least 12 weeks old for the test to be accurate. We include this testing in our kitten healthcare packages. Newly adopted adult cats are usually tested at their first wellness visit. Cats who spend time outdoors should be tested annually.

Is there a vaccine?

This requires two boosters given about a month apart. An additional booster is recommended at 1 year of age. This is because young animals are the most susceptible to acquiring the infection. The vaccination gives you some assurance that your kitten or young cat will be protected if he or she escapes outdoors or you decide to introduce another cat into the household.

We have a vaccine for FIV but it is not widely used and is not as effective as the FeLV vaccine. We see more FIV cases here at Best Friends than we do FeLV, but we are not able to offer a good way to prevent it.

Feline Infectious Peritonitis

FIP is a viral infection that until recently was uniformly fatal. Affected cats usually have distended abdomens full of straw-colored fluid but it can also be seen in “dry” form where there are lesions in the chest or abdomen without all the fluid. These dry form cases are much more difficult to diagnose. Other symptoms are weight loss, fever and vomiting.

FIP is in the Coronavirus family. All cats carry Coronavirus in their intestines, it is part of their normal flora. In some cats, the virus mutates and becomes more likely to cause illness. There are also genetic factors involved in whether a cat becomes ill. This disease can wipe out a cattery where many related individuals may be susceptible.

Crowded, stressful conditions, such as humane societies, foster the spread of FIP. Coronaviruses are hardy and can survive for months in warm, damp environments. Viral particles are normally shed only in the stool but some strains can have aerosol transmission.

Unlike FeLV and FIV, we do not have an easy, accurate test for FIP. Because most cats carry Coronaviruses, most cats will test positive, whether or not they actually have the mutated form of the virus. Furthermore, the vaccine for FIP was ineffective and was taken off the market years ago.

Until very recently, once a cat had symptoms from FIP the mortality rate was 100%. There is now an experimental drug regimen for FIP and a couple more antiviral drugs undergoing testing. We have one patient who is an FIP survivor but the drug itself, as well as monitoring and administration were all expensive, and the regimen required daily, painful injections.

Luckily, FIP is not nearly as common as the retroviruses. We worry about it most with purebred kittens and cats, or those that have been in crowded shelters or homes.

Rules to remember to help stop the spread of these fatal infections

  1. Keep your cat indoors. The more time spent outside, the higher the exposure to infectious diseases.
  2. Never bring a new cat or kitten into your household and let it interact with other cats or kittens until both new and resident cats have been tested and found negative for FeLV and FIV. Keeping new arrivals separate also reduces spread of respiratory infections and parasites. Wash your hands after handling either pet. Also wash your hands after handling any unfamiliar cats away from your home – you can bring respiratory diseases home to your pets on your hands, clothes or shoes.
  3. Vaccinate where possible. The risk of infection is generally much higher than the risk from vaccination.

Feline Herpesvirus infection

Rhinotracheitis, which is a Herpes virus, is the most common viral disease of cats. As with all Herpes viruses, once you have it, you will harbor it for life. Rhinotracheitis causes a mild disease in cats and kittens, much like the common cold in people. You may not realize that 90% of humans have Herpes simplex virus harbored in their nerve tissue from previous exposure to the Herpes simplex virus. Similarly, over 80% of cats, indoors or out, have been exposed and have Feline Herpes virus in their system.

Unless a cat’s immune system is compromised by feline leukemia, cancer or other problems, the initial Herpes infection that most kittens get will run its course in a week or two. Major disease or death from infection with Herpes is rare. However, the cat that has been infected, even mildly, harbors the virus in its system for the rest of its life.

When cats are stressed by other diseases, by use of steroid medications for allergies, or from moving to a new household, traveling, a new pet or baby in the house, or any other cause, they can shed Herpes virus from their systems again. Usually they will show no obvious signs of illness but virus can be found in their tears, nasal discharge or saliva. During this reshedding time, cats are contagious to other cats and kittens. This is why kittens often catch these viruses even though the adult cat in the house, or the cats around it at a humane society or pet store, have no symptoms of infection.

Some cats do show symptoms when their Herpes flares up. Just as some people get repeated Herpes cold sores from Herpes simplex virus in their system but most people don’t, some cats will repeatedly suffer from corneal (eye) ulcers or have chronic (long term) sneezing or nasal congestion. The immune system keeps the infection at bay for the most part, but it can’t get rid of it completely and the virus can flare up to cause disease. Some cats will develop eye ulcers or sneezing consistently whenever they become stressed or ill.

Persian and Himalayan cats are especially likely to have problems because their short nose makes them prone to dry eyes and they also tend to have weaker immune systems. Dental disease and sinus infections, which spread to the eyes via the tear ducts, are also more prevalent in these breeds.

Although vaccinations for Herpes virus in cats have been used for years they have made no difference in the prevalence of respiratory disease in cats. Cats that have been vaccinated have milder symptoms and get better faster, but they still get the virus, and they still shed it later on. Our goal is to minimize symptoms and keep your cat as comfortable as possible.

The injectable distemper vaccine all kittens and cats receive includes vaccination against Rhinotracheitis. We also have a nasalgen (nose drop) vaccine that works better to keep Herpes at bay than the injectable vaccine. Your cat will receive this nose drop vaccine for the first time at age two and then every 2-3 years long term. Cats with Herpesvirus flare-ups are vaccinated with the nose drop vaccine twice a year.

Vaccines and vaccine recommendations have changed several times over the past twenty years. More changes are likely down the road. Treatments have also changed and improved. We will keep you up to date on new developments so that together, we can provide the best care to your feline friends.