Laurie Anne Walden, DVM
Both indoor and outdoor cats need vaccines. Vaccination protects cats against infectious diseases that cause serious illness or death. This article describes the vaccines that veterinarians commonly recommend for cats.
One factor that affects vaccination protocols for cats—but not dogs—is the risk of injection-site sarcomas. Some cats develop these malignant tumors at the injection sites of vaccines or other substances. These cancers are uncommon (estimated to occur in 1 to 10 of every 10,000 cats vaccinated) but can be devastating. Although the vast majority of cats do not develop injection-site sarcomas, feline vaccination protocols are designed to balance the tumor risk with the need to keep cats protected from infectious disease. Recommendations include giving cats only the vaccines that are necessary, vaccinating cats no more often than necessary, and using vaccine formulations that are less likely to cause sarcomas.
Rabies vaccination is mandated by law for dogs and cats in the United States. In North Carolina, all cats, dogs, and ferrets aged 16 weeks and older must be vaccinated against rabies. Rabies vaccination laws are one reason this fatal disease is very rare in humans in the United States. Around the world, rabies kills tens of thousands of people every year.
Cats in North Carolina can and do get rabies. In 2017, cats were 1 of the 5 most common species to test positive for rabies in this state (after raccoons, skunks, foxes, and bats). The total number is low, but the risk is real.
Cats that live 100% indoors need rabies vaccines too. Cats sometimes escape outside. And sometimes the unexpected happens, like a bat getting into the house. The presence of a bat indoors is considered a rabies exposure unless the bat is caught and tests negative. A cat that is exposed to rabies but does not have a current rabies vaccination is subject to quarantine for up to 6 months. Also, a cat that bites a person must be quarantined for 10 days; cats without current rabies vaccinations typically spend this quarantine at a facility instead of at home. For more information, see the post about NC rabies laws.
In North Carolina, the first rabies vaccine a cat receives lasts for 1 year, and subsequent vaccines can legally be given every 3 years (as long as the vaccine is labeled for 3-year use). If your veterinarian recommends giving your cat a rabies vaccine every year instead of every 3 years, it’s probably because the clinic uses a feline rabies vaccine that is designed to reduce the sarcoma risk and is labeled for 1-year use. Most 3-year rabies vaccines on the market are killed-virus vaccines that contain adjuvants, substances that enhance the immune response. Killed, adjuvanted rabies vaccines have been associated with injection-site sarcomas in cats. A different type of rabies vaccine, a recombinant vaccine, does not contain adjuvants. The most common version of the recombinant rabies vaccine is a 1-year vaccine. Ask your veterinarian which type of rabies vaccine the clinic uses for cats.
Feline herpesvirus 1 (rhinotracheitis), calicivirus, and panleukopenia virus
Vaccines for feline herpesvirus 1, calicivirus, and panleukopenia virus are often included in a single combination vaccine. The American Association of Feline Practitioners (AAFP) recommends that all cats be vaccinated against these viruses as kittens (in a series of boosters), again 1 year later, and then every 3 years. In past decades, cats received these vaccines every year, but annual vaccination is no longer considered necessary.
Feline herpesvirus 1 and calicivirus are 2 of the main causes of feline respiratory disease complex. This illness spreads easily from cat to cat. People can also carry the infectious agents on their clothing, which is how indoor cats can be infected. Infection causes sneezing, discharge from the nose and eyes, conjunctivitis (pinkeye), fever, mouth ulcers, and eye ulcers. Some combination vaccines also cover Chlamydophila (Chlamydia) bacteria, which cause conjunctivitis in cats.
Feline panleukopenia virus is very contagious among cats, and infection can be fatal. The virus is similar to canine parvovirus. Like parvovirus, it destroys cells lining the intestine and impairs immune function. In kittens, it can also damage the part of the brain that regulates coordination and balance.
Feline leukemia virus
Feline leukemia virus is a retrovirus that suppresses immune function and causes cancer. Because the virus impairs immunity, infected cats develop a wide variety of medical problems. Most infected cats die within 3 years of diagnosis. There is currently no cure.
Vaccines against feline leukemia virus have been associated with injection-site sarcomas. For this reason, the decision to vaccinate an adult cat usually depends on the cat’s lifestyle and risk factors. However, the AAFP recommends vaccinating all kittens against feline leukemia virus. A nonadjuvanted recombinant vaccine is available.
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