FIV, FIP, and FeLV are three extremely serious, incurable, and usually fatal cat diseases caused by viruses. Each is caused by a different kind of virus. However, they are all contagious only between cats, and have the interesting quirk that not all cats exposed to them will get sick.
Unlike the viruses that cause upper respiratory diseases or distemper in cats and can be carried in the air, these three require the physical presence of an infected cat in the same place (although not necessarily at the same time) as the cat who catches it. FIP and FeLV are spread most often by prolonged close contact with an infected cat.
Close contact can include mutual grooming or sharing food, water, elimination areas, or sleeping quarters. This means a cat who goes outdoors and urinates or defecates where a cat carrying FIP or FeLV goes can catch the virus without ever having had physical contact with the carrier. FIP and FeLV can also be spread to kittens by a mother with the virus.
The main route of infection for FIV appears to be a bite from an infected cat. Cats who go outdoors -- particularly if they fight -- are therefore at risk. The most common profile of an FIV-positive cat is an unneutered male who goes outdoors and has sustained bites and scratches from other cats.
Cats who appear otherwise healthy may be carrying these viruses. Reliable blood tests exist for FeLV and FIV. There is a test for FIP; however, a positive FIP test alone -- without other symptoms or risk factors -- is not absolute proof the cat has the virus.
FIV is sometimes also called feline AIDS (or FAIDS). FIV does have a few general similarities to HIV, the virus associated with AIDS: It belongs to the same class of viruses, can stay in the body for years without causing illness, and when it becomes active, slowly breaks down the disease-fighting immune system. However, AIDS is a human disease, and FIV cannot infect humans.
What to Do
Take the test. Since a cat can appear healthy and still carry one of these viruses, a new arrival -- even your first cat -- should be tested for FeLV. Kittens probably don't need FIV tests unless they were strays, but it's probably a good idea to test adult cats from any source. Your veterinarian may recommend a retest in a few months. This isn't a scam; if your cat was very recently infected, it may not show up on the first test.
Stop the spread. There's only one surefire way to prevent your cat from contracting FeLV, FIP, or FIV: Keep her away from the sources of the viruses. In other words, keep her away from other cats and the places they frequent. This usually means keeping cats indoors at all times. It definitely means testing any new cat added to your household for FeLV and FIV before she's allowed to meet the resident cat or have run of any of the same areas. Preventative vaccines are available for FeLV and FIP. Schedule an appointment with your vet to talk about the advisability of vaccinating your cats for these diseases.
Be positive about positives. If your cat tests positive for FeLV or FIV and a retest confirms it, don't give up hope. With good care, FeLV- and FIV-positive cats can live for years, even after signs of disease appear. New treatments are coming all the time, and there may be a breakthrough that will help your cat long before she gets seriously ill.
Be responsible about the news. Keep your cat away from uninfected cats, and don't add any FeLV- or FIV-negative cats to your household. It may be tempting to start taking in other FeLV- and FIV-positive cats who are facing euthanasia, but think it over carefully. Eventually, the disease will catch up with them, and they'll demand a lot of time and resources. It may be best to focus on the special status of your own cat and give her the best possible quality of life.
Treat the symptoms. Most of what you can do for cats who are sick with FeLV, FIP, or FIV is just make them feel better. This might be as simple as indulging them with their favorite foods when their appetites are poor or coaxing them to eat with petting and hand-feeding. However, each virus has its signature complications that may also need attention, usually from the vet and with follow-up or nursing care at home. FeLV causes lymphosarcoma, a kind of cancerous tumor that may need to be removed.
The "wet" (effusive) form of FIP causes fluid to build up in the chest, making breathing difficult, or in the abdomen, giving the cat a bloated appearance. This buildup is a problem your vet can sometimes relieve by suctioning out the fluid with a needle and syringe. Since FIV attacks the immune system, you'll have to stay on top of secondary infections with prevention and medication.
When to Call the Vet
These three viral diseases are a strong case for annual veterinary checkups. The early signs of any of the diseases are often too subtle for the average cat owner to notice, but a veterinarian knows what to look for. In between checkups, notify your vet of any sudden abdominal bloating or swelling, low-grade signs of illness that never quite go away (sneezing or diarrhea, for example), any lumps on your cat's body, or bites or scratches from cats not known to be FeLV- and FIV-negative.
Cats who have been diagnosed with FeLV, FIP, or FIV should see the vet regularly.
DANGER LEVEL: All three of these diseases (FeLV, FIP, and FIV) are extremely dangerous. Although surprisingly few cats exposed to these viruses will get sick from them, once the illness begins it is almost always fatal.
Kidney disease in cats is not nearly as fatal as FIV, but it can still be quite serious. Learn more in the next section.