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Feline Immunodeficiency Virus (FIV)

Find out more about FIV in cats.
Written by Mayhew team
Updated 3 months ago

What is FIV?

Feline Immunodeficiency Virus (FIV) is a viral infection affecting domestic cats and other feline species. It is caused by a type of virus called a lentivirus. The virus causes cats to have a weakened immune system, leaving them more vulnerable to infection and disease.

The prevalence of FIV in UK animal shelters varies, but it is estimated to be between 3% and 11%. Its prevalence in the wider UK cat population is likely to be lower than 3%, and is most common in feral cat populations, especially among unneutered male cats.

How is it transmitted?

FIV is most commonly transmitted between cats through bite wounds inflicted by an infected cat. This is why un-neutered male cats are most at risk due to their territorial fighting.

Whether a cat becomes infected following contact with an FIV positive cat is dependent on many factors. For example: the type of contact between the cats, the level of virus in the FIV positive cat, the strain of the virus and the health of the cat exposed to the infection.

This virus cannot be passed from cats to humans.

What are the symptoms?

The virus can cause many different symptoms and can affect all parts of the body, from losing weight to brain damage. Symptoms include:

  • Weight loss and poor appetite
  • Diarrhoea
  • Recurrent fever
  • Lethargy
  • Enlarged lymph nodes
  • Inflammation of the gums and mouth
  • Wounds that don’t heal
  • Chronic skin disease or hair loss
  • Chronic or recurrent respiratory, ocular (eyes) and intestinal disease
  • Neurological disease

If you are concerned that your cat has been in contact with an FIV positive cat and is displaying any of the above symptoms, contact your local vet.

How are cats tested for FIV?

Cats may be tested for FIV during routine health screening or if they are showing symptoms associated with the virus. There are broadly two types of tests available: one identifies antibodies against the virus (for example the ELISA test) and the other test identifies the virus particles themselves (for example PCR testing).

Testing can be complicated and results should always be interpreted on an individual basis, taking into consideration factors such as the clinical signs of the cat, their age and the timing of the suspected infection. It is usual to test for both FIV and Feline Leukaemia Virus (FeLV) at the same time.

How does FIV affect cats?

FIV is an incurable disease, however it is a manageable infection with many cats living healthy lives despite being FIV positive. In fact, recent studies suggest that cats with FIV commonly live normal life spans, as long as they are not also infected with FeLV.

“Although the infection is permanent, the prognosis can be promising as long as it is carefully managed. Many FIV cats can live healthy lives.” Mayhew's Head Veterinary Surgeon, Justin Ainsworth.

When initially infected, cats may experience a few days of feeling unwell and may have a fever. This phase of infection normally resolves with little or no treatment required. The more severe diseases which can be associated with infection may not be seen for many years as FIV is a slow acting virus.

The virus affects the way the immune system functions. This can either result in a cat’s immune system being unable to effectively respond to infections, or the immune system might react in an abnormal way causing damage to the body.

The symptom most commonly associated with a reduced immune response in FIV cats is mouth infections. These infections can be very severe and require extensive medical treatment and dental work, including tooth extractions. Upper respiratory infections causing chronic nasal discharge (runny nose) is also frequently seen.

FIV positive cats can also be at a greater risk of certain cancers (for example lymphoma).  

Management of FIV positive cats

s FIV itself is an incurable disease, treatment is focused on management, from protecting your cat against common infectious diseases like cat flu to routinely bringing your cat in for dental check-ups.

With any FIV cat, it is still recommended to continue with routine health measures, including neutering, flea and worming treatment and vaccinations. Vaccinating against core diseases, such as cat flu, is important to help protect them as they may be less able to ward off these infections. Routine dental care is also important due to the increased risk of mouth infections.

Like all cats, FIV positive cats should have a veterinary consultation at least once a year to identify any early signs of disease, and should follow a healthy diet plan. It is generally accepted that raw food diets should be avoided in FIV cats due to the increased exposure to certain bacteria and parasites.

If an FIV cat is unwell, or the disease has progressed, the benefit and risk of vaccination and other care measures must be discussed on a case by case basis with a veterinary surgeon.

Multiple cat households*

Cats who have tested positive within a household of multiple cats must have a detailed management plan put in place following a discussion with their vets. Considerations would include: what preventative health measures should my cat receive, what outdoor access would be appropriate (for example an enclosed garden) and what is the risk to other cats in the household?

Theoretically, it is possible for cats to become infected by non-aggressive transmission (for example grooming each other or sharing food bowls), but this is thought to be very low risk. With appropriate management, FIV positive cats have been recorded to successfully live with other cats and not spread the infection.

*Mayhew rehomes confirmed FIV+ cats as single cats to avoid any risk of transfer to other cats, and as an indoor cat if the animal is clinically well and suited to an indoor lifestyle. This also helps to protect the rehomed FIV+ cat from exposure to infections from other cats, which may reduce the progression of FIV related disease.

Living an indoor life

If you have an FIV cat, you should keep them indoors, ideally with access to an enclosed garden. Any outdoor space should be enclosed so that your cat is not able to come into contact with other cats. There are many ways that we as cat owners can make sure an indoor life is still enriched, fun and active - here are just a few ideas!

Prevention of FIV

There is no licensed vaccine in the UK for protection against FIV. The FIV virus has several subtypes (strains) and frequently mutates making development of an effective vaccine challenging. One other challenge with vaccination is that it can interfere with test results making wider control and monitoring of the disease more difficult.

Prevention of the spread of FIV in the UK has focused on virus screening and management of infected cats. It is possible to test cats for FIV before introducing them into a new household, especially if they are viewed as high risk.

The importance of neutering cats cannot be emphasised enough as it greatly reduces their risk of contracting and spreading FIV. Neutering also reduces many other risks, including road traffic injuries.

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