Feline Immunodeficiency Virus (FIV)

Feline immunodeficiency virus (FIV) is the virus that causes feline AIDS, a disease similar to human AIDS, where the immune system is attacked and gradually weakened.

The virus is found in high levels in the cat’s saliva, and transmitted predominantly by bites, when an infected cat spreads the disease by biting an uninfected cat. Transmission can also occur by cats grooming each other and sharing food bowls. If an FIV positive cat is identified in a multi-cat household, a high proportion of the other cats in the household are likely to be infected.

Infection occurs in two stages. Initially the cat will have a fever lasting a few days to a few weeks, and occurring about 4 weeks after infection. Swelling of lymph nodes may also occur and can last for several months. This initial phase is often mild and may go unnoticed by the owner. Most FIV-infected cats recover from this stage of the disease after a brief illness, although in very young and very old cats even the first stage may be fatal.

The second stage occurs several months, or several years, after initial infection, presenting as an AIDS-like illness. The immune system becomes progressively weaker and infected cats are unable to fight off infection that they can normally cope with.

Clinical signs:

Symptoms in the immunosuppressed stage of the disease, when the immune system is not functioning properly, are caused by the secondary infections and are extremely variable. Infected cats may exhibit some or all of the following signs:

  • Decreased appetite
  • Weight loss
  • Scruffy appearance
  • Poor healing of wounds such as abscesses
  • Persistent or intermittent infections, particularly respiratory tract, urinary tract, skin, ear or eye infections
  • Persistent or intermittent diarrhoea
  • Infections of the mouth (stomatitis) and gums (gingivitis)
  • Anaemia
  • Behavioural changes due to neurological involvement

How is FIV diagnosed?

Diagnosis is made by a single blood test, which detects antibodies to the virus. A small proportion of FIV-infected cats may have too little antibody to be detected. Some cats in the very early stages of infection have not yet developed antibodies to the virus, and some cats in the end stages of infection are unable to produce antibodies as their immune systems are too weak.

Treatment protocols:

There is no specific treatment for feline immunodeficiency virus. Treatment is supportive and palliative, generally directed at secondary infections as they arise. Weight loss is a major feature of many clinically affected FIV infected cats, and it is important to ensure adequate dietary intake. Feeding high energy convalescent diets containing high quality protein is helpful.

An effective vaccine is available to protect your cat against feline immunodeficiency virus. The vaccine is not part of the core vaccines given to cats although we strongly recommend that all cat parents have their pets vaccinated against FIV.

The prognosis for FIV-infected cats is very unpredictable. Some cats may live for many years without any illness. Others may initially be very ill but make an excellent recovery and survive for months or years. An FIV positive result is not necessarily an indication for euthanasia, even in sick cats.

Given that FIV is primarily spread by fighting cats, it is almost impossible to prevent the spread of the disease. You can confine an unvaccinated cat at night to avoid fighting but this is not a practical way to minimise the risk of infection. The only way to completely protect against the disease, and to prevent your cat infecting other cats, is to have your pet vaccinated.