Often presented as an “optional extra” at vaccination, you might have wondered whether your cat actually needs “FeLV” or “Leukaemia” vaccination. In this blog, we’re going to look at why it’s offered…

What is feline leukaemia?

Feline Leukaemia is a virus (FeLV) that causes severe, and often fatal disease in cats. It causes suppression of the immune system by damaging white blood cells. This means they are unable to fight off infections, similar in some ways to human AIDS. Cats can display a variety of symptoms related to infections of all kinds, weight loss, fever, lethargy and weakness. Anaemia is quite common, too. 

Crucially, the damage to white blood cells can also cause types of cancers. 

The virus is found in the saliva, urine and bodily secretions of infected cats. It is transmitted by close contact, eg grooming, socialising or fighting with an infected cat. Kittens and young cats are more susceptible to the virus than older cats, as their resistance to FeLV increases as they get older. Infection with FeLV often drastically shortens a cat’s lifespan. Unfortunately, no cure exists to treat and eliminate FeLV from the body, so preventing infection with FeLV is recommended.

Is there a test for FeLV?

Generally, a blood test is highly recommended prior to vaccinating to check whether a cat has been infected with FeLV. If the cat is positive for FeLV, then the vaccine will offer no further protection so there is no benefit in administering it. These tests are generally reliable, however false-positive results can occur. So it may be necessary to repeat the blood test at a later date to confirm the results.

Should my cat be vaccinated for FeLV?

This should be assessed on an individual cat by cat basis, to assess their potential risk. A cat that lives completely indoors, with no contact with any other cats, or with uninfected housemates is not at risk of contracting the disease, so therefore vaccination is unnecessary. A playful, or active cat who spends a lot of time outdoors, gets into scraps with other neighbourhood cats will be at higher risk and vaccination is recommended. Generally, we advise that all kittens are vaccinated for FeLV, then on an as-needed basis for adult cats. Your vet will be able to discuss this further with you.

Is the FeLV vaccine safe?

The vaccination has been developed to provide immunity against FeLV so it does not cause the disease. Like with any other vaccination, mild side effects can occur and sometimes your cat may be quiet or a little lethargic for 12-24 hours after the vaccination, which is normal. However, if you are concerned contact your vet for advice. 

A rare but aggressive type of cancer called an injection site or vaccine-associated fibrosarcoma has been associated with a reaction to some components of FeLV vaccines. Relative to the number of vaccinations administered the incidence of this is very low. The exact cause is still unknown but seems to be related to a post-injection inflammatory reaction. In general the benefits of vaccination outweigh the risk, in most situations. Some vets administer the FeLV vaccination under the skin in the back leg rather than in the scruff of the neck to allow easier treatment if, although rare, it should occur.

How often does my cat need vaccinating?

To provide lasting immunity, your cat will need an initial course of 2 injections, 3-4 weeks apart. These can be given from 9 weeks of age in kittens. As immunity wanes over time, re-vaccination will be required. The most common current UK vaccination protocol is to vaccinate against leukaemia every 3 years, but this may vary based on your cat’s lifestyle. Other cat diseases such as feline flu and enteritis also require repeat vaccination, the frequency of which varies based on their risk and the vaccine used.

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