Cat health

Feline Leukaemia Virus (FeLV)

Feline Leukaemia Virus (FeLV) is a retrovirus that is similar to a more common virus known as Feline Immunodefeciency Virus (FIV).

What is Feline Leukaemia Virus?
Feline Leukaemia Virus (FeLV) is a retrovirus that is similar to a more common virus known as Feline Immunodefeciency Virus (FIV). Many cats can overcome the infection, however if they become persistently infected FeLV may cause cancers, immunosuppression and reproductive problems, amongst other conditions.

How do cats catch FeLV?
FeLV is passed from cat to cat via saliva. Unlike FIV which is transmitted via biting, the transfer of FeLV is usually between friendly cats. This usually occurs during grooming or by sharing food bowls. Occasionally mothers can pass the infection to their kittens either in the womb or via milk. Kittens are particularly susceptible to contracting persistent infections, whereas most adult cats are able to eliminate the virus. Once a cat beomes persistently infected, it remains so for life.

How common is the disease in Australia?
The infection rates in most of Australia are very low compared to the rest of the world, with most infections occurring in catteries where contact between cats is close. The prevalence in Western Australia (7-11%) is higher than that of the Eastern states (<2%).

What are the signs of infection?
The signs of FeLV infection are not directly due to the virus itself, but rather it’s effects on the infected cells. Cancers of the bone marrow and immune system are frequently seen, as well as immunosuppression (increasing susceptibility to infections), or red blood cell depletion leading to anaemia. Sometimes the signs of FeLV infection may be vague and non-specific, such as weight loss, lethargy and inappetence. If there are abortions or stillbirths within a breeding cattery, FeLV infection may be the cause.

How is FeLV diagnosed?
FeLV is usually first detected via a test which looks for viral protein within the blood. A single positive test in a healthy cat does not necessarily mean that the individual is persistently infected. A repeat test in 3 months is needed to check whether the virus has been eliminated from the body. If a second test is positive, then a confirmatory test (such as immunofluorescence) should be performed at a commercial laboratory. This confirmatory test should also be performed if the first test is positive in a cat that has a disease that may accompany FeLV infection (for example, lymphoma).

How is the disease treated?
Unfortunately there is no treatment that will eliminate the virus once a cat becomes persistently infected. Management involves supportive care and antibiotics for secondary infections. Treatment of cancers may be attempted with chemotherapy. The prognosis for persistently infected cats is generally poor once signs of disease have occurred.

It is recommended that positive cats be kept indoors to protect them against communicable disease such as cat flu, and to also prevent the FeLV virus from spreading. Routine worming, flea control and vaccination are advised.

Can FeLV infection be prevented?
There are several vaccines available for FeLV. These work by stimulating the immune system to help prevent persistent infection. Unfortunately none of the vaccines have been shown to be 100% protective and there are links between the use of FeLV vaccine and certain tumours, called sarcomas. It is therefore recommended that you discuss the risks versus benefits of the vaccine with your own vet to ascertain if vaccination is appropriate for your cat. Generally, because the risk of exposure is very low in Australia and the fact that the majority of adult cats are able to clear the infection, routine use of the FeLV vaccination is not necessary in most cases, however this should be verified by your veterinarian.