Immunodeficiency is a medical term that refers to the body’s inability to develop a normal immune response, therefore feline immunodeficiency virus (FIV) refers to a complex retrovirus that causes an immunodeficiency disease in cats. FIV is in the same class of viruses as HIV, human immunodeficiency virus, the causative agent of AIDS (acquired immunodeficiency syndrome). FIV is estimated to infect between 14-29% of the Australian cat population.!


FIV is a retrovirus, and retroviruses replicate by inserting a copy of their genetic material into the DNA of a host cell. As it spreads throughout the body FIV destroys the body’s immune cells. Lentiviruses represent a genus of slow viruses with long incubation periods, and being a lentivirus like HIV, FIV can take months or even years of lying dormant in a cat’s body before causing symptoms. Most cats infected with FIV are asymptomatic, but have an increased susceptibility to developing other infections and some types of cancer.


What’s the difference between FIV and Feline AIDS?

FIV is not the same as Feline AIDS, even though the terms are often used interchangeably. The relationship between them is similar to HIV and AIDS in people, with AIDS being the end stage of the virus that occurs after the latency period. Feline AIDS is an outcome of an FIV infection whereby the cat is clinically unwell. However FIV infection doesn’t necessarily lead to AIDS, and some FIV positive cats may carry the virus but never develop the disease.


How is FIV spread?

While FIV and HIV share many similarities, one of the main differences is how they’re spread.  FIV is transmitted between cats and is primarily found in their saliva. It’s more likely to be spread between males due to their being more aggressive than females, and because of their roaming natures. Transmission usually occurs through scratches and bite wounds, commonly inflicted during territorial battles, and it can sometimes also be contracted at birth. Sexual contact is not a major method of spreading FIV in cats even though it has been detected in semen. The chances of infection increase with age, but there is no genetic predisposition for infection.


The disease is not spread easily by casual contact such as by cats grooming each other, and the sharing of food bowls, water bowls, and litter trays, should be relatively low risk. A high risk of infection exists for cats who get into fights where bites puncture their skin.


Can humans catch FIV?

Being highly species-specific viruses, FIV can’t infect people, and HIV can’t infect cats.



What are the symptoms?

Symptoms for cats infected with FIV can be diverse due to their decreased ability to develop a normal immune response. Symptoms, and things to watch for include:


  • Recurring minor illnesses, especially upper respiratory and gastrointestinal
  • Persistent diarrhoea
  • Enlarged lymph nodes
  • Inflammation of the gums
  • Eye disease - inflammation of the front of the eye including the iris, and glaucoma
  • Chronic kidney problems
  • Long-term, or recurrent infections of the external ear and skin resulting from bacterial or fungal infections
  • Cancers such as lymphoma
  • Nervous system abnormalities - behavioural changes, disruption of normal sleeping patterns, vision and hearing changes, disorders often affecting the nerves in the legs and paws
  • Fever
  • Anorexia - especially in later stage



How is FIV diagnosed?

The three most common cat viruses in Australia are herpesvirus, calicivirus, and panleukopaenia, after which come FIV and leukaemia virus (FeLV). FIV is much more common than FeLV but the immunodeficiencies caused by FeLV and FIV can’t be distinguished.


In order to diagnose FIV, your vet will conduct a thorough physical examination of your cat, as well as a complete blood profile which includes chemical blood profile, blood count as well as a urinalysis (urine tests). Bacterial, viral or fungal infections will firstly need to be ruled out and tests for parasites and tumours will also be required before a final diagnosis can be made.



There are no specific treatments such as anti-viral drugs for FIV, and in most cases it is not necessary to treat infected cats provided they are healthy. If they become ill, the complication that has occurred is treated instead, and this can help to prolong life for cats in the terminal stages of the disease. Outpatient treatment is normally provided to cats who have become ill, unless they are severely dehydrated.


Your veterinarian will first work to manage any secondary infections. While this concurrent infection will not usually cause disease, your cat’s weakened immune system will give it entrée and they will cause further complications in your cat’s overall health.


Surgery may be necessary for dealing with infected teeth and for the removal of tumors. A special diet plan may also need to be put into place.




How much monitoring your cat will need from you depends on secondary infections and other manifestations of the disease.


You will need to watch for the occurrence of infections in your sick cat, and be aware that wasting or severe weight loss may occur, and that your pet may eventually die of this disease. But, in general, the earlier FIV is detected, the better your cat’s chances are for living a long and relatively healthy life.


“Within 4.5 to 6 years after the time of infections, about 20 percent of cats die; however, over 50 percent will remain without clinical signs of the disease.” (4) In the late stages of the disease, when wasting and frequent infections are most likely to occur, life expectancy is less than a year. Specifically, inflammation of the gums and mouth may not respond to treatment or may be difficult to treat.




In order to prevent this disease from occurring in the first place, you should vaccinate your cat against the virus, and protect your cat from coming into contact with cats that are FIV positive. You will also want to quarantine and test new cats that are coming into your household until you are sure that they are free of the virus. “It is important to note that some cats will test positive for FIV if they are carriers, although they may never have symptoms of the virus, and that cats that have been vaccinated against the virus will test positive for it even though they do not carry it.


Euthanasia is not normally called for when a cat has tested positive in part because of these reasons. If your cat has tested positive you will need to talk to your veterinarian about what to do to prevent possible transmission to other cats, and what symptoms to be watchful for, should they occur.




To answer some of the most frequently asked questions about FIV, we consulted with Dr. Niels Pedersen of UC Davis School of Veterinary Medicine; Virginia Corrigan, DVM of the Virginia-Maryland College of Veterinary Medicine; and Richard Meadows, DVM, DABVP of the University of Missouri, College of Veterinary Medicine.



1. What’s the best way to prevent a cat from getting FIV?


"The virus is present in the saliva of infected cats, so FIV is usually transmitted between cats through bite wounds. It can also be transmitted via sustained contact with an infected cat or from an infected mother cat to her kitten. All cats should be tested for FIV when they are kittens and after any exposure to a potentially infected cat, particularly if there was a bite wound.  Cats that are FIV-positive should be kept inside and separate from non-positive cats. Cats that go outdoors and come in contact with other cats outside are at the highest risk," Corrigan says.


One of the best routes for prevention, Richard Meadows, DVM, suggests, "Spaying and neutering cats decreases fighting behavior and preventing access to FIV positive cats."


2. What are the physical and emotional changes that happen to a cat that has FIV?


Put simply, by Corrigan, "Most infected cats are asymptomatic and feel well. They can live a normal life and have a normal life expectancy. However, they are more prone to developing secondary infections and certain types of cancer."  Meadows adds, “FIV should not be looked at as a death sentence since many cats with FIV can live apparently healthy and happy lives for years. Over time the FIV infection does progressively suppress the immune system and this will result in physical decline (weight loss, secondary infections, neurological problems, etc)."


"Cats are rarely seen in the acute stage of the disease, where you might observe fever, enlarged lymph nodes, vasculitis, and white blood cell changes,” Pendersen explains, “More often the acute stage of infection goes unnoticed and it is many months or years later that the more common signs of the chronic infection occur. Signs of immunodeficiency often include chronic oral and nasal infections, skin infections, and intestinal infections.  Some FIV infected cats develop chronic neurologic disease, often manifested by vague changes in behaviour."


3. What are the stages of FIV?


"There are basically three stages.  The primary stage lasts for 2-4 weeks or so and usually resolves spontaneously, but can sometimes be very severe and lead to death.  This is followed by a variable, but often very long latent stage where the cats remain outwardly healthy.  The terminal stage occurs as long as 7-10 years later, but sometimes sooner, and is manifested by diseases associated with immunodeficiency or cancer," Dr. Pendersen says.


4. How is FIV like HIV?


Dr. Pendersen further explains, "FIV tends to be a milder disease and terminal disease often occurs later in life, if at all.  HIV is a much more serious disease with higher mortality if untreated with antiviral drugs."


5. Are certain breeds more susceptible to getting FIV?


"No, any breed of cat can get FIV,” Corrigan says.


6. Can FIV be passed from mother cat to kitten?


"Experimentally, using high levels of exposure, the mothers can transmit FIV to the kittens. It is controversial whether or not this occurs in nature. However, kittens born to FIV positive mothers in the clinically asymptomatic stage may test positive for FIV for the first four to even six months of life without becoming positive for FIV after that time. This likely reflects antibodies from the mother circulating in the kitten’s blood stream early in life," Meadows says.


7. What are the best treatment options for cats with FIV?


Simply put, there is no specific treatments. "There are no safe and effective anti-viral drugs for FIV so this is not an option," Pendersen explains,” Fortunately, it is usually not necessary to treat them as long as they are healthy. When they do become ill, we try to diagnose whatever complication that occurs and treat it if possible. This can prolong life for a long time in many FIV infected cats in the terminal stages of the disease.  There are several biologics that are being touted on the web as having immunostimulatory properties and to be effective in prolonging the lives of FIV infected cats. We believe these to be expensive and ineffective.  Interestingly, a recent study demonstrated that FIV infected cats forced to live in crowded and unsanitary multi-cat environments had a much higher mortality and died earlier than FIV infected cats that lived as normal household pets.  This suggests that the stresses of such environments had a negative effect on FIV infection.  We are also often surprised how well some FIV infected feral toms, showing definite signs of FIV disease, respond to proper care and diet.  We believe that many FIV infected toms become too ill too effectively hunt for themselves in nature and actually attach themselves to homes where people will provide them food and shelter. Many of these cats eventually return to normal health with proper diet and go on to be castrated and become regular pets, living normally for many more years."


Corrigan suggests that, "Raw meat and dairy products should be avoided. Regular dental care is also very important, as they are prone to developing inflammation and infection of the teeth and gums. There are some medications that may help stimulate the cat’s normal immune response. FIV positive cats should be kept indoors and separate from FIV-negative cats in order to avoid spreading the virus."


8. Does FIV affect male or female cats more often?


According to Meadows, male cats are affected by FIV more often. "This is primarily associated with the roaming behavior (searching for breeding partners) and defense of territories both of which are more intense in intact male cats than in other cats,” he says.


  1. RSPCA Australia Knowledgebase Article ID: 691 23 Feb, 2017 Revision: 4