Herpes in Cats
March 6, 2011
Question: Dr. Saenger, could you write a column about feline herpes? I do a lot of work with feline rescue and we occasionally foster a kitten that has had a bad upper respiratory virus, presumably herpes virus. Can these kittens be adopted into homes with other cats? Is the vaccination for the upper respiratory viruses good enough to protect the older cats?
Answer: This is a great question, and one that we face at Bees Ferry Veterinary Hospital every day. This is because most kittens have been exposed to some kind of upper respiratory virus at the breeder’s, the shelter or from the wild. And usually, the adopting owner already has other cats living at home.
About ninety percent of kitten upper respiratory infections are caused by herpesvirus (also called rhinotracheitis) and calicivirus. The symptoms are sneezing, runny nose, runny eyes, fever and sometimes, painful ulcers in the mouth. There are often secondary bacterial infections as well. The infections are spread by the wet sneezes of the infected cats. Fortunately, this is not the same strain of herpesvirus that affects people, so we don’t have to worry about humans getting herpes from their cat.
Most cats with one of these viruses acts just like you or me with a cold and it runs its course in about 7 to 10 days. Some cats, especially kittens can get quite sick and require veterinary prescriptions to help them recover, but the important thing here, is that, unlike our colds, once infected with herpesvirus, always infected with herpesvirus. The same is true with calicivirus.
Once a cat has recovered from his or her initial “cold”, he may seem very normal, but stresses such as surgery, boarding or introduction of a new pet can induce the herpes to re-activate and cause symptoms such as another runny nose or runny eyes. When this happens the cat will shed the virus for two weeks. These episodes may recur for life, although they typically get less severe as the cat matures. Cats with calicivirus may shed the virus continuously, even if they are not showing symptoms. In other words, a cat with herpes is contagious to other cats for a few weeks after a stressful event. Cats with calici are contagious for several months after infection, but do not appear to have recurrences of symptoms like herpes cats do.
So, what can you do to minimize the chance of a new kitten passing herpes or calicivirus on to your mature cat? Well, if you are good cat owner, you are having your cats annually checked out by your veterinarian and your cats are up to date on vaccinations for herpes and caliciviruses. (This is the RCP or FVRCP vaccine that you see on your pet’s records) Individual cats who stay indoors all the time may only be receiving their vaccinations once every three years, which is adequate in most circumstances, but if you bring in a kitten, it might be a good idea to boost that vaccine in your adult cat. Your veterinarian can help you with that decision.
You need to think of these vaccinations like we think of the flu vaccine in people. Vaccination does not guarantee that you won’t get the flu, but if you do, your symptoms should be much less severe. Adult, healthy cats who are vaccinated for herpes and calicivirus tend to do very well around younger, infected cats, as long as the cats are separated during a fulminant outbreak of symptoms.
Here is what I would recommend for this reader. Treat the affected kitten in his foster home until his or her symptoms are gone for two weeks. Meanwhile, booster vaccinations in the adopting owner’s home. When the kitten moves to his new home, keep the cats separated for the first week, washing hands between handling the kitten and the older cat. Then follow general guidelines on stress-free introduction of cats to each other. You cannot guarantee that the new cat won’t have recurrences or that the older cat won’t get the sniffles, but you will have minimized the chances, and odds are with you that all will be well.