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homefamily pet handoutsfeline leukemia virus and feline immunodeficiency virus


We feel it is critically important for you, as a cat owner, to understand some simple facts about Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV or Feline AIDS), so that you may protect your cat from exposure since both of these viruses are fatal.

Feline Leukemia Virus is spread through the saliva from a cat harboring the virus. It must be spread by direct contact because when the virus hits the air, it can only live for 30-60 seconds before it will be inactivated. The virus can be passed from one cat to another by grooming, eating together, touching noses, or spitting at each other in a fight or through a window screen. Once this exposure has occurred, each cat will respond to the virus based on its own immune capabilities. Twenty-eight percent of the cat population has a strong enough immune system to allows the cat to eliminate the virus from its body. Another 30% of the cat population is unable to do this and can succumb to degenerative diseases that will kill the cat within its first one to three years of life. The last 42% of the population is able to build some immunity, but unable to eliminate the virus completely. These cats harbor the virus in their bone marrow, so that if we run a blood test looking for the virus, it will not be found. This is called a latent infection. Of this 42%, most will be able to eliminate the virus within 6-12 months; however, 10% of exposed cats will persistently carry the virus latent. If a latently infected cat gets stressed for any reason, they may start shedding the virus. During this time a blood test would be positive for the infection.

Latent carriers are a medical challenge. Our current recommendation is to test all cats for FeLV. If a kitten is tested when it is less than 12 weeks old, its immune system is so underdeveloped that it might test negative. Therefore they should be retested after 12 weeks of age. Stray cats should be tested initially, and again three months later. The incubation time for the virus can be as long as three months, so the test should be repeated in case they were just recently exposed to the disease. If we get a negative test result at the appropriate time for a kitten or cat and it remains healthy, we may never recommend testing the cat again. If the cat is often sick with colds, infections, or other medical problems, we may test this cat multiple times in an attempt to reveal the cat as a latent carrier.

A vaccine for FeLV is available. However, due to an increased risk of vaccine-induced tumors associated with this particular vaccine, we only recommend vaccinating cats who go outdoors and have a high likelihood of exposure to the virus via contact with stray cats.

Feline Immunodeficiency Virus is also a contact virus shed through the saliva. The difference is that when FIV leaves the body and touches the air, it is inactivated immediately, not in 30-60 seconds. The way cats give the virus to other cats is by biting them and actually depositing the virus into the tissue of the other cats. FIV is very similar to the human immunodeficiency virus in that it has a long incubation period of five to seven years and it may take this long for it to be detected. It affects the immune system in the same way, making the cat more susceptible to infections. Eliminating possible exposure to other cats and keeping them from fighting is the best protection. This virus will NOT infect humans!

These concepts may seem complicated. Please feel free to ask us any questions concerning these viruses. It is very important to us that you understand how to protect your cat from possible exposure. We want your cat to live a long and healthy virus-free life.

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