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Pet Health

Understanding FIV in Cats: Symptoms, Care, and Prevention

Feline Immunodeficiency Virus (FIV) weakens cats' immune systems, making them more susceptible to infections. Despite the lack of a cure, with proper management and reduced stress, FIV-positive cats can live relatively normal lives. Learn about transmission, symptoms, and how to care for a cat with FIV to ensure your feline friend enjoys many loving years with you.

Dr. Bethany Hsia

June 26, 2024

What is FIV?

Feline Immunodeficiency Virus (FIV) is a significant virus affecting cats worldwide, which targets their immune system. Over time, cats with FIV may become more susceptible to "opportunistic infections"—those caused by organisms that a healthy immune system would normally defeat. Although there is no cure for FIV, with appropriate management and a reducing stress in the environment, cats diagnosed with the virus can lead relatively normal lives for several years. It is important that pet parent’s with a cat who has been diagnosed with FIV understand that even though the disease affects a cat's immune system it does not preclude a quality life. Rest assured that with the right care, your beloved feline can still share many loving years with you.

How Common is FIV in Cats?

The presence of Feline Immunodeficiency Virus (FIV) is a global concern, yet the frequency of infection can vary substantially depending on the region and the cat population in question. For seemingly healthy cats in North America, the rate of FIV infection floats between 2.5% and 5%. Rates ascend appreciably among felines in suboptimal environments suffering a heightened susceptibility to the virus — these cats can exhibit infection rates upward of 15%.

Cats who spend time outdoors, and particularly those that may engage in territorial battles (usually intact males), often bear a greater risk of contracting FIV. Given there is no effective vaccine available, the emphasis on other preventive measures becomes all the more important. For the safety and well-being of your cats, consider keeping them indoors to prevent encounters with potentially infected cats, and ensure that FIV testing is part of the health screening of any new cats added to your home.

Myths and Misconceptions about FIV

There are several misconceptions surrounding FIV that need to be addressed for a clear understanding of the disease. Firstly, while FIV is a virus in the same family as the human immunodeficiency virus (HIV), it is a highly species-specific virus that infects only cats. While the disease can infect both domesticated and large cats, it is not a threat to humans. Secondly, the primary mode of FIV transmission is through bite wounds, therefore homes with an established hierarchy where cats do not fight are unlikely to see the spread of FIV within the home. Another reason casual infections are uncommon is that the FIV virus cannot survive for more than a few hours in most environments.

Why FIV is a Serious Concern for Cat Owners

FIV is a significant worry for pet parents of a positive cat because it targets the cat's immune system. A cat with FIV has weakened defenses against other infections, which could be otherwise easily fought off in a healthy cat. Unfortunately, while FIV-infected cats can look perfectly healthy for years, they may be gradually becoming more vulnerable to severe illnesses caused by common pathogens. Often, by the time signs of FIV become apparent, the cat's health has already been significantly compromised. Which is one reason why routine veterinary care and health screenings are recommended to safeguard your feline friend's health.

Transmission of FIV

How FIV Spreads Among Cats

As previously discussed, the primary mode of FIV transmission is through bite wounds from an infected cat. Naturally, this means free-ranging outdoor cats are at higher risk, especially those with territorial behaviors that lead to fighting. However, indoor cats or those that have enclosed access to outdoor spaces such as catios, are at much lower risk as they are unlikely to receive bites from unknown cats. In addition to bites, FIV can be transmitted to the kittens of an infected pregnant queen and through sexual contact, neither of which is a significant source of infection. Fortunately, prevention of contact with unknown cats and FIV screening of cats your feline family members will be exposed to are quite manageable.

Preventing FIV Transmission

Preventing FIV transmission is a crucial aspect of managing this disease. One of the most effective ways to reduce the risk of FIV infection is to keep cats exclusively indoors or in enclosed outdoor spaces, thus limiting their exposure to potentially infected cats. If you have an FIV infected cat it is crucial that you do not let them roam outside where they may spread the disease to neighborhood or feral cats.

When welcoming a new cat into your home, ensure that they have been screened for FIV and that their status is known. Ideally, only FIV negative cats are brought into a household with other negative cats or FIV infected cats into a home with existing FIV infected cats. While casual encounters such as social grooming and sharing of water bowls are not a source of infection, the introduction of a new cat is sure to upset the social hierarchy and may lead to fighting, bites, and transmission of FIV. Unless you will be keeping the cats in separate areas it is ill-advised to bring an FIV infected cat into an FIV negative household and vice-versa.

Symptoms and Progression of FIV

Early Signs of FIV

In the acute phase of FIV infection cats often suffer from fever, depression, lymph node enlargement and decreased appetite; this may occur 1-3 months after the initial exposure. Because the signs are mild and somewhat vague they are often missed by owners or attributed to other causes of lymph node enlargement and fever. It is important to be aware of these early signs of FIV and seek veterinary care promptly to stay apprised of your cat’s FIV status and manage potential risks of opportunistic infection.

How FIV Affects a Cat's Health Over Time

After the acute phase cats enter an asymptomatic phase that may last months or years and some cats never progress beyond this period of latent infection. WHile the cat doesn’t show any outward signs of illness, the virus continues to replicate. Over time, FIV significantly impacts the immune system by killing protective immune cells (T-lymphocytes), hyperactivation of the immune system leading to the exhaustion of the remaining immune cells, as well as causing blood disorders such as anemia, thrombocytopenia and neutropenia, all contributing to generalized immune deficiency.These changes occur in a slow insidious progression making it difficult for pet parents to detect, underscoring the importance of regular veterinary check-ups and wellness screenings.

Advanced Signs of FIV

As the immune system becomes increasingly weakened leading into the advanced stage, cats are more susceptible to secondary infections from pathogens in their normal environment which had previously been easily fended off. These infections are often chronic and often require longer and more intensive treatment in FIV infected cats than they would in a cat with a normal immune system.

Additionally FIV infected cats are subject to excess inflammation in a host of tissues. Most commonly, a painful inflammation of the cat's gums and mouth or of the middle layer of the eye (uveitis). Recent research shows a link between FIV infections and the development of myocarditis, inflammation of the heart muscle. The prevalence of FIV associated myocarditis remains to be seen, but the existence of a link requires attention to be paid to the health of the heart as well as their oral and ocular health.

The Link Between FIV and Other Diseases

FIV is closely linked to other diseases due to its significant impact on a cat's immune system. The virus reduces the ability of the cat's immune system to respond to other infections, making it difficult for the cat to recover from diseases that it would typically combat. As a result, many of the clinical signs associated with FIV are actually due to other non-healing infections. Your cat may be diagnosed with a seemingly simple infection but if it is not resolved quickly with the proper care, FIV should be strongly considered as a possible complicating factor.

As mentioned above, FIV infections can lead to other serious immune related diseases such as anemia (decrease in healthy red blood cells), thrombocytopenia (decrease in platelets which are responsible for clotting and wound healing), neutropenia (decrease in the white blood cell whose job it is to attack foreign organisms in the body), and lymphoma (cancer of the lymphatic cells and tissues). This underscores the importance of comprehensive veterinary care in managing FIV and the associated health complications.

Diagnosis and Treatment of FIV

How Vets Diagnose FIV

Diagnosing FIV begins with a blood test that screens for antibodies to the virus. Most veterinary hospitals are able to run this test in house rather than needing to send samples to a laboratory, meaning results are known quickly. A positive test result means that the cat has produced antibodies to the virus, indicating that it is likely that the cat has been — and is still — infected by the virus. It's important to note that being FIV-positive is not the same as having feline AIDS. An FIV-positive diagnosis means that the cat has been infected by the virus, but it may be years, if ever, before the cat develops the level of immunocompromise and clinical signs we think of as being associated with AIDS.

False Negatives

It is important to note that with screening tests there are a few cases in which a cat may have a false negative result, meaning the test is negative but the cat is infected with FIV. The incidence of false negatives is low and the test is relatively quick and easy to run, making this test a good method of screening for infected cats. A false negative may result when a cat has been recently exposed to the virus but the immune system has not had time to develop enough antigens to register on the test. In this scenario, retesting at 60 day intervals is recommended up to 6 months post exposure.

Another, less common, reason a false negative may occur is when a cat with advanced FIV is severely immunocompromised and their system can no longer produce enough antibodies to register. In this case other changes will be evident on bloodwork and additional testing (Western Blot Test) can be done to search for parts of the virus called antigens. Finally, there is some concern that the antibodies to global FIV variants may not be as readily detected by our domestic tests. This would be another instance for confirmation by Western Blot testing to look for the antigen of the FIV virus.

You may wonder why the Western Blot test is not the first line of testing if it is used to confirm results. This is because it is a specialty test which must be sent out to a referral laboratory and requires more blood for the sample, takes longer to run, and can be more expensive.

False Positives

False positives may also occur with any screening test, these happen when the test is positive but the cat is not infected. One reason a test may be falsely positive is if kittens are nursing from a mother who is infected. They will receive maternal antibodies through the milk and trigger a positive test result. In this case nursing kittens should be retested every 60 days up to 6 months of age before a positive test result can be considered an accurate representation of their own antibodies.

Another reason for a false positive FIV result comes from previous vaccination. Up until 2016 a vaccine was available for FIV, this was pulled from the North American market due to limited effectiveness and the danger of false positive results. The job of the vaccine is to induce the body to make antibodies and the FIV screening tests are unable to distinguish between antibodies from the vaccine or from infection. Fortunately, this vaccine was not commonly given nor part of the core vaccines recommended by the American Association of Feline Practitioners (AAFP) for healthy cats.

Caring for a Cat with FIV

Currently, there is no cure for FIV. However, cats infected with FIV can still lead very normal, healthy lives for many years if managed appropriately. The primary concern for a cat diagnosed with FIV is reducing their risk of acquiring secondary infections and comes with the responsibility of preventing the spread of FIV to other cats. The first step in addressing both concerns is managing your cat's exposure to other cats. Keeping your cat indoors will help immensely. If you feel the need to give your cat outdoor time, restrict access to leash walks or a secured and enclosed area such as a catio. It is important to make sure your cat is not stressed by the outdoor time, if they feel exposed to other neighborhood cats or dogs without a place to hide or escape the stress will be counterproductive to the benefits of being outdoors.

Spaying or neutering is recommended for a myriad of reasons but plays a role in decreasing the spread of FIV as well. We have established that FIV is most often spread by bite wounds; these are often the result of territorial fights and other hormone driven behaviors. While sexual contact is not the main source of FIV infections it can contribute to the spread of FIV as well as the growth of the cat population in general. What’s more, kittens may be infected with FIV in utero. It is a good idea to spay or neuter your pets for their health and for the health of the population.

Routine vet visits are recommended every 6 months for FIV infected cats to monitor their overall health, paying special attention to their gums, eyes, and keeping records of their weight. And don’t wait until the 6 month checkup to bring your cat in if there are signs of illness or significant behavioral change. While vigilance is important for catching secondary infections, your FIV-positive cat can live a long and happy life so don’t forget to enjoy it.

Long-Term Prognosis for Cats with FIV

The long-term prognosis for cats with FIV can vary depending on comorbidities. Many cats who receive veterinary attention in the early onset of secondary infections are able to enjoy many years and can even reach the average lifespan for an uninfected cat. A few negative prognostic indicators to keep in mind are persistent fever and consistent unintended weight loss. These may indicate comorbidities such as lymphoma, severe secondary infection, or coinfection with Feline Leukemia Virus (FeLV) and will have a more guarded prognosis.

Maintaining a Healthy Lifestyle For an FIV-Positive Cat

Feeding and Exercise Tips for FIV-Positive Cats

Feeding and exercise are crucial elements in caring for any cat but all the more for FIV-positive cats. Cats with FIV should be fed nutritionally complete and balanced diets without any raw ingredients such as raw meat, uncooked eggs, or unpasteurized milk to minimize the risk of food-borne illness to which they may be more susceptible. Maintaining multiple fresh clean water sources. Regular exercise is also important to maintain the physical health and well-being of any cat. You can engage your cat in interactive play with feather wands, toys, and laser pointers, or give them their food in puzzle toys. Cat trees are a great way to encourage appropriate climbing and well-being as cats love to hide on high perches.Providing your cat with mental stimulation and opportunities to engage in routine light activity are the best ways to support their immune health.

Monitoring Behavior Changes in Cats with FIV

As mentioned before, close monitoring of the health of FIV-infected cats is crucial. Often signs will manifest as small changes in behavior or attitude. While these signs can be indicative of any number of causes, staying aware of your cat’s normal habits and noticing small changes can give you a head start in identifying a brewing illness. You may wish to make notes on what you observe and see if you identify any patterns, then if you feel there is reason to be concerned you can share your observations with your cat’s veterinarian.

Living with an FIV-Positive Cat

Hopefully you feel encouraged knowing more about FIV and the ways it can be managed and kept from spreading. Our goal is to show that a healthy cat should not be euthanized based on a positive test result alone. This disease may eventually rob the cat of their health but as long as the cat is living with a good quality of life, they should be allowed to continue to do so. You can help enrich your FIV-positive cat’s life and potentially lengthen it through prevention and early detection of secondary infections, nutritious and balanced diet, healthy levels of activity and the love that you provide.


Dr. Bethany graduated from the University of Illinois College of Veterinary Medicine in 2010. After graduation, she moved west. Dr. Bethany spent a year at a small animal exclusive practice in Washington state, where she was first introduced to in-home euthanasia.  Read More

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