Feline Leukaemia Virus (FeLV)
FeLV infects domestic cats throughout the world. Cats at greatest risk include outdoor cats residing in multi-cat environments or cats living with other FeLV-infected cats. The prevalence of infection varies greatly depending on a cat’s age, health, environment, and lifestyle. In the United States, approximately 2 to 3% of all cats are infected with FeLV. Rates rise significantly-13% or more-in cats that are ill, very young, or otherwise at high risk of infection.
Transmission is through transfer of virus in the saliva or nasal secretions resulting from prolonged intimate contact. The virus may also be transmitted by transfusion of blood from an infected cat, in utero, or through the milk. Kittens are the most susceptible to infection; resistance increases with age.
Clinical signs of infection include inappetence, lethargy, weight loss, pale or yellow mucous membranes, vomiting, diarrhoea, reproductive problems, and increased susceptibility to other infections, leukaemia and tumours. Death usually occurs within three years.
The decision to vaccinate an individual cat against FeLV infection should be based on the cat’s age and its risk of exposure. That is, cats not restricted to a closed, FeLV-negative indoor environment. Protection is not induced in all vaccinates, thus making preventing exposure to infected cats the single best way to prevent infection.
If vaccination is deemed appropriate, annual revaccination is recommended. Cats should be tested for FeLV infection before initial vaccination and when there is the possibility that they have been exposed to FeLV since they were vaccinated.