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Feline Immunodeficiency Virus (FIV) in Cats

Outdoor cat
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Severity: i Medium - High
Life stage: All
  • FIV stands for feline immunodeficiency virus.
  • Like AIDS in humans, FIV impacts a cat's immune system and makes it difficult to fight diseases.
  • FIV is transmitted through bites or scratches from infected cats. FIV+ mothers can pass the virus on to kittens.
  • Cats can have FIV for months or years without showing symptoms.
  • Treatment for cats with FIV is limited and focuses primarily on supportive care.

Feline immunodeficiency virus (FIV) in cats is a disease that causes severe immunosuppression in cats. Cats with FIV can be infected for long periods of time without showing clinical signs. But once the signs of the disease appear, it is hard for cats to overcome. 

As the name suggests, feline immunodeficiency virus in cats is related to human immunodeficiency virus (HIV) and the disease syndrome parallels that of HIV in people. Since FIV attacks the immune system, infected cats are often more prone to secondary infections or opportunistic infections (rare infections that most healthy cats can fight off). 

What is FIV?

FIV in cats is caused by a pathogenic lentivirus in the Retroviridae family that destroys cells of the immune system. As a lentivirus, FIV has a high probability of mutating and appears as various subtypes. There are roughly six common subtypes with varying degrees of severity.

FIV causes immunosuppression in cats by attacking CD4+ T cells, which are important cells that assist the immune system, keeping most cats healthy. The lack of a robust immune system makes them less able to fight off other diseases. 

How Do Cats Get FIV? 

Outdoor cat scratching

Cats can contract FIV through bites and bite wounds from the saliva of infected cats. 

Risk factors for FIV are associated with lifestyle and activities of domestic cats. Any cat breed can be affected, but the disease is seen more commonly in cats that are prone to fighting or biting. Adult and male cats are most at risk due to their lifestyle, and intact, male cats are the highest risk group for catching the virus. Cats that have a history of bite wounds or abscesses and cats that have access to the outdoors are also at risk. 

FIV-positive cats can live in the same household as other cats as long as they are not prone to fighting or biting each other. Luckily, FIV is not spread through feces, aerosolized particles, social contact such as grooming, or through contact with materials such as blankets and toys.  

Kittens can be born with FIV and FIV can be passed from mothers to kittens. Transmission from an infected queen (mother) to kittens is possible during pregnancy and during lactation. This doesn’t always happen, but when it does, it is usually due to the amount of virus present in the mother’s bloodstream. If the mother cat is carrying high viral loads, she will be more likely to pass the infection to her kittens. 

Symptoms of FIV in Cats 

Lethargic cat on couch

Signs of FIV vary widely in cats. Most of the clinical signs are non-specific and can correlate with a number of other diseases. Pet parents should always consider or mention FIV testing to their veterinarian when they see their cat’s health declining especially if your cat has unsupervised outdoor access.

Signs of FIV in cats include:

  • Weight loss 
  • Fever 
  • Abnormalities of the eye 
  • Depression
  • Lethargy
  • Enlarged lymph nodes 
  • Halitosis (bad breath) 
  • Diarrhea
  • Dehydration
  • Behavioral changes (abnormal mental activity) 

FIV infection can present in different stages. There are four stages of infection, but not all cats experience each of the stages. 

Acute phase stage 

The acute phase occurs soon after infection and signs include lethargy, fever, and enlarged lymph nodes. Some cats may not show any signs during this stage.

Latent stage

After the acute phase, the infection is asymptomatic and enters into the latent phase, which means the infection is lying dormant. This stage can last for months to years.

Acquired immunodeficiency syndrome (AIDS)

The AIDS stage can occur years after the initial infection and result in secondary infections or immune-mediated diseases. Signs during this stage are most often associated with secondary infection and/or chronic or intermittent disease. 

Terminal phase

The terminal phase of FIV often consists of signs of neurologic disease or cancer. Once cats have entered the terminal stage, they usually have a survival time of 2-3 months. However, by the time the disease is diagnosed, they may have poor quality of life and humane euthanasia may be the most kind option.

Diagnosing FIV in Cats 

Veterinarian feeling cat lymph nodes

Veterinarians will use a series of tests to diagnose FIV in your cat. Veterinarians will start with a physical exam to look for certain signs such as enlarged lymph nodes, fever, abnormalities in the mouth and the eyes. 

Next your veterinarian will obtain blood from your cat to submit a variety of tests (such as a complete blood count or biochemistry profile) to rule out other diseases. Other blood tests include serology, PCR, or virus isolation which can be used to test specifically for FIV antibodies or the live virus. 

How to Treat Feline Immunodeficiency Virus 

Treatment options for FIV-positive cats are very limited and rarely implemented. Supportive therapy is the most important line of treatment because cats with FIV are more prone to concurrent infections. Supportive care encompasses a variety of strategies that will keep your cat as healthy as possible. 

These strategies include:

  • Treatment for secondary infections
  • Feeding a healthy, balanced diet
  • Maintaining proper hydration
  • Anti-inflammatory drugs
  • Immune-enhancing drugs
  • Probiotics
  • Parasite (such as flea and tick) control

Many infected cats have a good quality of life for several years, until they begin to show signs of FIV. 

How to Prevent Cats from Getting FIV 

Man playing with cat

FIV prevention is centered around reducing the risk of exposure which includes neutering male cats, limiting access to the outdoors, and decreasing the likelihood of fighting or bites among cats in the same household. 

If you have an infected cat, it’s important to keep him indoors to prevent spreading the infection to other cats and to minimize their exposure to other infectious agents. FIV doesn’t survive well in the environment and can be killed by common disinfectants. 

There is a FIV vaccine, but its efficacy is variable. In some cats, the vaccine has been shown to cause a false positive on a blood test [1]. This vaccine is considered a non-core vaccine by the American Association of Feline Practitioners (AAFP) and should be reserved for at-risk cats. 

Staying on top of knowing your cat’s FIV status could be an easy way to catch the disease early. The recommendations by the AAFP to test for FIV include cats in the following conditions: 

  • All cats, periodically based on risk 
  • New cats joining a household or group setting 
  • Any cats exposed, more than 60 days after exposure 
  • Sick cats 
  • Before initial FeLV or FIV vaccination

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