FIV in Cats

Feline Immunodeficiency Virus in Cats

Cat at the vet
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About FIV

Feline immunodeficiency virus (FIV) is a virus that can cause a multitude of health problems in cats due to reduced immune system function. It can cause an acquired immunodeficiency syndrome sometimes called feline AIDS.


FIV is a virus from the same family as human immunodeficiency virus (HIV), but it is a separate virus specific to cats. It cannot be transmitted to humans or other species.

There are several subtypes of the virus. Once a cat is infected, it will be infected for life. However, the percentage of cats that will go on to develop reduced immune function from the virus is unknown, and it can take many years for such problems to develop. Therefore, a positive diagnosis of FIV does not automatically carry a bad prognosis, and is not a death sentence.

Transmission and Risk Factors

FIV is spread mainly via bite wounds. Therefore, cats that fight are at the highest risk of being infected with FIV, such as cats allowed to roam outdoors and male cats (which tend to fight, especially when not neutered). It can also be transmitted from infected mother cats to their kittens.

Signs and Symptoms

After first being infected with FIV, cats may experience transient symptoms including:

  • Fever
  • Enlarged lymph nodes
  • Low white blood cell count

Cats generally recover uneventfully from this phase and may then appear healthy for some time, often several years.

However, the virus can gradually attack and weaken the immune system, leading to a host of secondary health problems.

The course of illness with FIV is difficult to predict, but generally, any of the following may be seen when immune system function deteriorates:

  • Enlarged lymph nodes
  • Weight loss
  • Loss of appetite
  • Recurring fever
  • Diarrhea
  • Infections (e.g., mouth, skin, respiratory, gastrointestinal, urinary tract)
  • Cancer
  • Neurological signs (e.g., behavior changes, seizures)

Diagnosis of FIV

FIV infection is diagnosed by a blood test to detect antibodies to the virus. There are several methods of testing (each with pros and cons), and often more than one is used to confirm a result. Multiple tests over time may also be needed to completely rule out FIV, depending on the situation.

Treatment of FIV

Once infected, a cat will remain infected for life, and treatment is often focused on managing diseases resulting from diminished immune function (e.g., antibiotics for infections). Medications that strengthen the immune system such as interferon and Imulan (a new veterinary drug) can be used, and antiviral drugs such as AZT may also be tried in some cases. Your vet will recommend a course of treatment that is right for your cat.

Alternative Medicine

A variety of alternative medicines and therapies have been used to help manage FIV.

Because FIV is such a complex disease, such therapies should be planned in consultation with a vet well versed in alternative therapies.

Prevention of FIV

Keeping your cat indoors is probably the single most effective way to prevent infection. Neutering male cats is also important, to cut down territoriality and fighting. Test any new cats for FIV before introducing them to your household.

There is a vaccine available in the US and some other countries, but the use of the vaccine is controversial. The vaccine is not 100 percent effective, leaving some vaccinated cats susceptible to infection with FIV. However, all vaccinated cats will test positive for antibodies to FIV, so it is impossible to determine if a vaccinated cat becomes infected (i.e., wasn't protected by the vaccine).

Positive tests due to vaccination are also very problematic for shelters that euthanize FIV-positive cats. The advantages and disadvantages of vaccination should be discussed with your vet.

Caring for a Cat with FIV

A cat with a diagnosis of FIV can live for many years, and there are several precautions that can be taken with FIV cats to help manage the disease:

  • FIV positive cats should be kept indoors - to prevent exposure to possible infectious agents and also to prevent them from transmitting the virus to other cats.
  • Visit your vet at least twice yearly for routine check ups to catch any potential problems early on.
  • Monitor FIV positive cats closely for any signs of illness and seek treatment as soon as possible.
  • Feed a high quality diet and nutritional supplements as recommended by your vet. However, avoid raw diets as they may contain bacteria and parasites that could negatively affect an FIV infected cat.
  • Effective flea treatment should be used, as fleas can transmit diseases to cats.
  • Maintain routine vaccination protocols and parasite control programs. Regular dental care is also recommended.
  • Introduce new cats to the household slowly to ensure non-stressful/non-injurious interactions.

Multi-Cat Households

There is minimal risk of transmission of FIV between household cats that get along well. Discuss your specific household situation and inter-cat concerns with your vet. Removing an FIV positive cat from the home is generally not necessary.

All cats in the household should be kept indoors, kept up to date on vaccinations, and health concerns addressed as soon as possible; i.e. don't wait if your cat is "quieter than normal" or not feeling well.

Please Note: this article is intended for informational purposes only. If your pet is showing any signs of illness, please consult a veterinarian as quickly as possible.