FIV: Definitive Guide To The Feline Immunodeficiency Virus

December 18, 2018

The Feline Immunodeficiency Virus (FIV) is categorized as a lentivirus – a genus of slow viruses belonging to the family of retroviruses, characterized by a delay in the onset of symptoms/a long incubation period after infection occurs. FIV belongs in the same family of viruses as the Human Immunodeficiency Virus (HIV). As retroviruses are specific to the species, FIV will only infect felines, just like how HIV will only infect humans. FIV in cats is fairly common.

Despite being in the same retrovirus family, FIV should not be mistaken with the Feline Leukemia Virus (FeLV). These two diseases are often mistaken for the other as they cause similar secondary conditions, but they are quite different genetically and protein composition.

FIV is a disease that can be found worldwide, able to infect both domesticated and wild felines. It is most prevalent in wild, outdoor cats, as well as in heavily [feline] populated areas. Male cats are more prone to contracting FIV as compared to female cats, and high-risk cats (e.g. Those with weak immune systems) are more susceptible to FIV as compared to healthy cats (15-20% as compared to 1-5% respectively). Infection is most commonly seen in middle-aged cats (5-10 years). As such, because bite wounds and scratches are the most common causes of transmission, the disease most frequently infects free-roaming, outdoor male cats. Other forms of transmission include sexual transmission and transmission during birth (in utero/through mother’s milk).

Stages of Infection
FIV has three stages of infection: acute (initial), latent (asymptomatic), and the final stage.

During the acute stage, the virus causes mild symptoms such as lethargy, fevers, swollen lymph nodes, and weight loss. Additionally, the infected feline may experience increased susceptibility to skin and/or intestinal infections. This stage occurs 4-6 weeks after exposure to the virus.

During the latent stage, visible signs of infection, do not occur. The duration of this stage ranges from a few months to a few years. Immunodeficiency occurs during this stage, and when it reaches a severe level, the final stage occurs.

During the final stage, the infected feline will be extremely susceptible to contracting secondary diseases/infections. Oftentimes, these diseases would not normally cause severe problems in healthy cats, but the immune system is unable to fight off said diseases due to the heavily impaired state of the system of a cat with FIV. Common diseases and infections include respiratory tract and intestinal infections. When a disease progresses into a later stage, the life expectancy of the infected feline is shortened drastically.

Clinical Signs of Disease
In addition to the signs observed during the acute stage of FIV, these are the clinical signs of disease:

  • Chronic Oral Infections: One of the most common signs of FIV infections (approximately 50% of FIV infected felines will develop an oral infection), oral infections include inflammation of the gums (gingivitis) and mouth (stomatitis), as well as a constant bad odor around the mouth. Cats suffering from oral infections will experience pain when touched on the face and will have difficulty eating, which will in turn lead to weight loss.
  • Respiratory Tract Diseases: Occurring in approximately 30% of FIV infected felines, respiratory diseases include sneezing, inflammation of the nose, nasal discharge, and pneumonia.
  • Ocular Diseases: These include discharge from the eyes, inflammation of the cornea, cloudiness of the cornea, and glaucoma.
  • Neurological Diseases: As FIV can affect the brain, some cats will suffer from neurological diseases. These include changes in behavior, loss of house-training (e.g. Being unable to use the litter box), and disruption of regular sleep patterns.
  • Skin and Ear Infections: As a weakened immune system is unable to fight off parasites and bacteria, FIV infected felines will often suffer from skin and ear infections. These include hair loss, itching, and the development of pustules. Chronic ear mite infections and abscesses can also occur.
  • Gastrointestinal disease (i.e. Diarrhea)
  • Anemia
  • Lymphoma/Leukemia

Usually diagnosed through blood tests, FIV is detected through the presence of antibodies to the FIV virus found in the blood. If the test result shows that there are antibodies present in the blood, the feline is determined to be FIV positive. Note that multiple tests are recommended in order to confirm a positive or negative result, as no test is fully accurate.

If the blood test comes up negative, it does not necessarily mean that the feline in question is FIV free. As it takes a considerable amount of time (8-12 weeks on average) for a detectable level of antibodies to appear in the blood, cats should be retested in 3 months if potentially exposed to FIV.

Cat owners should note that it is possible for infected mothers to pass on FIV antibodies to her kittens, which may then lead to a positive result on the FIV test even if they did not contract FIV. These antibodies, however, can be cleared from the kittens’ systems over the course of a few months, until they hit six months of age. When these antibodies have been purged from their systems, the kittens will then be tested negative for FIV. Therefore, kittens should be retested after they turn six months old to see if they have contracted FIV.

Management & Care
Currently, there is no treatment that targets the FIV virus, but there are treatments that can help an infected feline cope with secondary infections caused by the virus. For example, the veterinarian may prescribe medication for secondary diseases, anti-inflammatory and immune-enhancing drugs, as well as electrolyte and fluid therapy if the feline is experiencing dehydration.

FIV infected felines should be kept indoors in order to minimize exposure to infectious agents carried by other animals and to prevent the spread of FIV to other felines in the neighborhood. Infected felines should also be neutered or spayed.

Infected cats should be placed on a healthy and nutritionally complete diet – uncooked food and any unpasteurized dairy food items should not be fed to infected cats due to the higher chances of them contracting diseases through bacteria and/or parasites present in these foods.

Checkups should occur at least twice a year, and owners of FIV infected cats should be on a constant lookout for any declines in health.

Although untreatable, felines suffering from FIV can live for many years if provided with the best care. Keeping felines indoors and away from stray cats can best prevent FIV infections. If there is a possibility that your cat has been exposed to FIV, FIV testing should be performed as soon as possible. An early detection can help the feline – and the rest of the family – cope more easily with the disease.

Image Credit
Photo by Rocky Mountain Feline Rescue - CC BY 2.0

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One comment on “FIV: Definitive Guide To The Feline Immunodeficiency Virus”

  1. My Patchy is FIV positive and is now 19 + years old. Twice, vets tried to convince me to euthanise her because of her FIV status and because she was allowed to go outside. They treated her like she was carrying the plague. It took a while, as I got her as an indoor/outdoor cat, but eventually she discovered the joy of doing her business indoors. Prior to this it had made it impossible to keep her indoors. What has been remarkable is that she has been in perfect health—the vets description, not mine—all her life, excepting an injury to her knee. Of course, now, she is exhibiting the effects of old age, but that is not related to FIV. My message—love them and keep them, and bring them for periodic check-ups, but don’t let anyone tell you to euthanise them. Patchy has been a beautiful and much-loved companion. I wouldn’t trade her for anything. And, yes, I changed vets from the ones who wanted to euthanise her to ones who weren’t put off by her FIV status. is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon properties including, but not limited to,,,,, or

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More information here. does not intend to provide veterinary advice. We go to great lengths to help cat owners better understand their pet cats. However, the content on this site is not substitute for veterinary guidance.

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