As a cat owner, you have likely heard of “kitty AIDS,” or feline immunodeficiency virus (FIV). Like human AIDS, kitty AIDS attacks the immune system, leaving your cat more susceptible to contracting illnesses. By determining your cat’s FIV status, you can make appropriate lifestyle choices that will help keep your feline friend happy and healthy for years to come. 

What is feline immunodeficiency virus?

The feline immunodeficiency virus belongs to a group of viruses called lentiviruses. Lentiviruses typically cause disease that progresses slowly, and infected cats may remain healthy for many years. However, an FIV infection is permanent, meaning cats cannot clear the virus, and the pathogen will always be present in their saliva.

FIV infects white blood cells, damaging their ability to protect the cat with a functioning immune system. Since FIV develops slowly, when the cat becomes infected, their immune system will mount a response, keeping viral replication at a relatively low level. During the first few weeks after infection, the signs are so mild, they generally go unnoticed. After a period of time—often two to five years after infection—some cats will experience an increase in viral replication, and develop disease signs.

How is feline immunodeficiency virus transmitted?

Since the virus resides in infected cats’ saliva, the most common transmission method is through a cat bite, where the infective saliva is injected into another cat. Rarely, the virus can be spread through mutual grooming, sharing food or water dishes, or blood transfusions, and from a pregnant mother to her kittens. 

How common is feline immunodeficiency virus among cats?

Although you’ve likely heard of FIV in cats, it’s relatively uncommon in typical cat households. FIV is most frequently encountered in outdoor cats, intact cats, or cats in crowded living conditions where fights are common. Male cats are twice as likely as females to have FIV—largely because they fight over mates and territory—and middle-aged cats are the most commonly diagnosed age bracket.   

What are the signs of feline immunodeficiency virus?

Once a cat is infected with FIV, disease usually occurs through immunosuppression. Since the immune system is not up to the task of battling infectious agents, infected cats are more likely to develop recurrent infections, or diseases that gradually worsen. These infections also may not respond to treatment as well as normally expected.

No specific clinical signs are associated with FIV, since the disease attacks the immune system, and allows other infections to create illness. Some common signs seen in infected cats include:

  • Weight loss
  • Waxing and waning fever
  • Lethargy
  • Enlarged lymph nodes
  • Gingivitis and stomatitis
  • Chronic or recurrent respiratory, eye, or intestinal diseases
  • Chronic skin disease
  • Neurologic disease

Chronic or recurrent infections that are difficult to fully eradicate are the most common FIV issue, since infected cats fail to respond to treatment as well as cats without FIV. 

How is feline immunodeficiency virus diagnosed?

Because FIV has no specific clinical signs, appropriate testing is determined through a sick cat’s signs, lifestyle, and potential exposure risk. If you’ve recently welcomed a stray cat into your home, and they are simply not responding to medication for an upper respiratory infection, FIV may be the culprit. Fortunately, several tests—including a rapid, in-house snap test—can detect FIV presence. We recommend testing each new cat who enters your household for infectious diseases, such as FIV and feline leukemia, before introducing them to your current kitties. 

An excellent in-house FIV test is available, but this rapid snap test does have a couple of drawbacks.

  • The test operates on the principle that an infected cat will always have FIV antibodies present, and detects only FIV exposure, not an active infection. For example, if you rescue a kitten who was born to an infected mother, they may test FIV-positive, because they received antibodies through their mother’s milk. A repeat test is recommended for young kittens after five to six months, to ensure their maternal antibodies have faded.
  • Another false-positive result can occur in cats who are vaccinated against FIV, since the antibodies will be present. We do not recommend vaccination against FIV, since a reliable vaccine has yet to be developed. 

If there is any doubt about the in-house test’s results, additional testing can be performed for confirmation.

Unsure about your cat’s FIV status? Have you welcomed home a stray cat? Our Mill Creek Animal Hospital team can allay your fears about this virus. Give us a call, and schedule an FIV screening test for your feline friend.