What is feline leukemia?
Feline leukemia is a cancerous disease caused by feline leukemia virus (FeLV). FeLV causes diseases other than leukemia including other cancers and immunodeficiency. Cats may not start to show signs of disease for months or years after being infected with FeLV. Infection with FeLV is a major cause of illness and death in domestic cats. Approximately 2.3% of cats in the United States are infected with FeLV.
What are the characteristics of feline leukemia virus?
FeLV is a type of virus called a retrovirus. That puts it in the same family as feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV, the virus that causes AIDS).
- Retroviruses are species-specific. This means a feline retrovirus will only infect cats; a human retrovirus will only infect humans.
- Retroviruses are made up of RNA. In the host, the RNA is transcribed into DNA and incorporated into the DNA of the host's cells.
- Retroviruses are fragile, being easily inactivated by ultraviolet light, heat, detergents, and drying.
- Retroviruses are widespread in nature, and have occurred for many millions of years.
How common is FeLV infection?
It is estimated that 1-2% of otherwise healthy cats are infected with FeLV. Males are more commonly infected than females, and cats with access to the outdoors are more at risk of becoming infected than indoor cats. Kittens are much more susceptible to FeLV infection than adult cats.
How is the FeLV transmitted?
Large amounts of FeLV are excreted in the saliva. Therefore, the most common mode of transmission is through mutual grooming. Nose-to-nose contact, and shared food and water bowls can also be sources of infection. Bites are a very efficient way to transmit FeLV.
FeLV can also be found in lesser amounts in tears, urine, and feces. Thus litter boxes could be a source of infection in multi-cat households or catteries.
FeLV can also be transmitted across the placenta (in utero) and through the milk.
It takes large amounts of virus to infect an adult cat, so usually prolonged contact or a bite is necessary for transmission.