Feline Leukaemia

Feline leukaemia virus (FeLV) is an important viral infection of young cats in multi-cat households. Over the last few years infection has become less common.

What diseases are associated with FeLV?

FeLV infection suppresses the immune system making the cat susceptible to secondary infections and chronic diseases that would not affect a normal healthy cat. These include mouth ulceration, cat flu, and fungal infections.

Cancers of the white blood cells and solid tumours such as lymphoma cause 10-25% of FeLV deaths.

Anaemia and other blood cell abnormalities are very common in FeLV infected cats. Other FeLV-related diseases include abortion, fading kittens, diarrhoea, neurological or nervous system signs, and immune-mediated disease.

Around 80-90% of persistently FeLV-infected cats will die within 3.5 years of diagnosis.

How is the virus transmitted?

The virus is transmitted by direct contact between cats during grooming or sharing of litter trays and food bowls over a long period of time.

The virus is fragile and does not survive for long in the environment.

An infected queen passes the virus on to all her kittens if she carries them to term. However, this is uncommon as infection with FeLV usually causes infertility or abortion.

What happens when a cat is exposed to FeLV?

Not all cats exposed to FeLV go on to develop FeLV-related diseases. Most cats eliminate the virus from the body, although some remain latently infected for a few months before they  conquer the virus completely.

In cat colonies where the virus is endemic only 30% of cats are persistently infected with FeLV and go on to develop FeLV-related disease. These cats are responsible for the transmission of FeLV to other cats.

How do we diagnose FeLV?

A test at the surgery detects FeLV virus in the blood of a persistently infected cat.

A negative result is always negative. Your vet will assess the predictive value of a positive result by taking your cat’s environment, housemates and outside access into account.

Cats in the process of eliminating the virus will test positive. A second test performed 8-12 weeks after the first test confirms persistent infection.

Is there any treatment for FeLV infection?

There is no treatment that eliminates the virus from the body.

Infected cats should be desexed and confined indoors to prevent exposure to infectious agents and other cats.

Because FeLV-infected cats are more susceptible to disease, vaccination for the common viruses that cause cat flu and enteritis is very important.

We treat secondary infections and other problems like mouth ulcers as they arise.

Most FeLV-infected cats eventually die of their infection or we elect to euthanase them if they are suffering.

Can we prevent infection?

If possible do not house your cat with a known infected cat. Any new cat to the household should test negative for FeLV.

If all the cats in the house are FeLV negative, confinement indoors will prevent casual exposure to wandering cats with the virus.

Breeders may prevent FeLV infection by blood testing all cats and isolating infected individuals.

Vaccination of cats in contact with other infected or potentially infected cats is advisable. As with other vaccines, an initial course of two injections is required, and annual boosters are necessary to maintain immunity.

Cat FIV and AIDS

Freddy came in last week off his food and drooling a lot. When I looked in his mouth I found a red raw gums and mouth. No wonder he was so flat and uninterested in life. 

Many infectious agents contribute to sore mouths like Freddy's. Freddy tested positive to FIV  (Feline Immunodeficiency Virus), which predisposes infected cats to mouth ulceration.  His owners have 2 other cats and a baby and had lots of questions about FIV and feline AIDS.

FIV is prevalent in Australian cats but testing positive for FIV is not the same as having feline AIDS.

Feline AIDS describes the terminal stages of disease which may not occur for many years - or at all! A positive FIV test means that your cat has been infected by the virus.

Are my family at risk?

No. Although FIV belongs to the same family of viruses as HIV in people, it only infects cats. There is no risk of cross infection of either virus between species.

Are other cats in the household likely to be infected?

The virus is shed in the saliva of infected cats and spread by biting. Cats with a history of cat bite abscesses are more likely to test positive for FIV.

Spread between cats in a household is unlikely unless they fight. Normal social interactions such as grooming rarely transmit FIV.

The best way to minimise the chances of FIV infection is to confine uninfected cats indoors away from aggressive cats.

How is FIV diagnosed?

FIV is diagnosed with a blood test at the surgery which detects an immune response (antibodies) to the virus. If this test is positive your cat is infected.

Kittens with immunity passed on from their mother may test positive until 4 months of age. If a young kitten tests positive we retest them at six months of age.

Will my cat recover?

Once a cat is infected with the virus it remains infected for the rest of its life but not all infected cats  become ill.

What diseases does FIV cause?

Like HIV, FIV suppresses the body’s defences so that the cat is vulnerable to diseases it would normally  defeat. The cat is vulnerable to chronic or recurrent infections that fail to respond to regular treatment.

These include:

1. Inflammation of the mouth and tongue leading to appetite loss, drooling and mouth pain
2. Weight loss
3. Poor appetite
4. Fever
5. Signs of brain dysfunction such as aggression, unequal pupils, convulsions and behavioural changes
6. Swollen lymph glands
7. Unusual infections like toxoplasmosis, cryptococcosis, chronic flu, pneumonia, skin disease
8. Tumours especially those of the lymph system

The non specific signs of weight loss, poor appetite and fever occur in many diseases of cats and are usually unrelated to FIV. Cats with FIV are more likely to suffer from these signs and diseases more often and  be less able to throw them off even with treatment.

FIV positive cats have a shorter life expectancy on average than FIV negative cats.

Is there any treatment?

Secondary infections with bacteria or fungi are treated with antibiotics and anti-fungals but no specific treatment for the virus is available. Trials with anti-HIV drugs such as AZT have reduced mouth inflammation in affected cats but the cost and availability of AZT makes its use in general practice difficult at present.

Anti-inflammatory treatment reduces mouth inflammation and peps up the appetite in many cats.

Should I have my cat euthanased?

Certainly not on the basis of a positive FIV test!  Like humans with HIV, cats with FIV appear healthy and happy for a long time before getting sick.

On the other hand if your cat has succumbed to multiple infections, is no longer responsive to treatment or is suffering from a chronically painful mouth then euthanasia is the kindest solution.

How can I help my cat?

Confinement indoors of an FIV positive cat  reduces the risk of infection with other agents. It also reduces the risk of transmission of the virus to other cats.

A good quality, highly palatable diet as well as worming every 3 months and at least annual health checks will enhance the disease free period.

Infections require prompt and aggressive treatment.

How do we prevent FIV infection?

Desexing and confinement indoors, especially at night, reduces fighting and therefore the risk of infection. We recommend vaccination with FIV vaccine for all cats with access to the outdoors. Cats older than 6 months of age are tested for FIV before the first vaccination. A series of three primary vaccinations is given 2-4 weeks apart and then a booster is given annually.