FIV: Feline Immunodeficiency Virus

As I mentioned in one of my Floofenstein posts, I knew as soon as the vet said she was calling to give us Floofenstein’s bloodwork results that something was wrong. That something was FIV, or feline immunodeficiency virus. Thankfully, our vet put my mind at ease right away by letting me know that cats with FIV commonly live average life spans.

While that alleviated my immediate concern, I still had some questions: does he need any additional vaccinations? Should he have more frequent vet appointments? Do we need to worry about keeping him separate from our other cats? Is there anything special we should know? And, of course, I wanted to know more about FIV. So, with this post, I’m sharing my research with you, and providing my vet’s answers to all of the questions I’ve asked her so far.

Like my post about FIP, this post will be more technical. I’ve provided my sources at the bottom of this post for you to read through. Where I need to include technical terms, I’ve either provided a link to a web page with a plain language explanation or my own explanation on my Veterinary Definitions and Resources [def] (definition) links.

Before I really dive into this, I want to say that there is some contradictory information out there. Some of that is likely because of different publication dates — even if there aren’t major updates, new information is regularly discovered. I’ll make sure to note when information shared below is not universal.

What is FIV?

The short answer: Feline immunodeficiency virus (FIV) is a cat-specific viral infection that infects cells of the immune system, damaging them, thus compromising their normal function.

The long answer: FIV is a retrovirus — a virus that enters the body, attaches itself to the host immune cells, and inserts its genetic material into the cell, which means it uses the host cells to multiply. The reproduction of the virus can take some time.

It was first recognized in 1986 and has since been found in cats worldwide. It is both one of the most common and consequential infectious diseases of cats and one of the most common causes of infectious diseases in cats globally. That said, a relatively low number of cats worldwide are infected. Depending on the source, 1-10% of the global feline population is FIV positive. It is unclear if this refers only to domesticated felines or if it includes wild cats.

FIV is usually more common where there are a lot of unneutered cats mixing together and fighting. Understandably, it’s much more common in outdoor cats and, perhaps unsurprisingly, is roughly twice as common in male cats.

The number of cats infected with FIV varies by geographic location. Because outdoor cats have a much higher chance of contracting FIV, regional variations in indoor versus outdoor populations likely account for geographical differences in infection rates.

Cats with FIV may seem healthy for many years, but FIV will eventually cause a decline in an infected cat’s immune system, meaning they will struggle to fight off infections that a healthy cat can. They are more susceptible to fungal, protozoan, bacterial, and viral infections — even normally harmless infections could potentially cause severe illnesses — and are at an increased risk of cancer and blood-related disorders.

Is FIV the same as feline AIDS?

FIV can progress to feline acquired immunodeficiency syndrome (AIDS) — similar to the HIV to AIDS transition in humans. However, simply being FIV-positive does not mean a cat has feline AIDS. An FIV screening test only indicates that a cat has been infected by the virus.

Not all FIV-positive cats progress to the feline AIDS phase of the disease, more commonly referred to as the progressive phase. However, if the disease does continue to progress, it may be years before an infected cat develops the clinical signs referred to as feline AIDS.

What are the symptoms of FIV?

Technically, FIV itself doesn’t have many symptoms beyond the initial phase. FIV infection comprises three phases: acute, latent, and progressive/feline AIDS.

Acute

After infection, the virus is carried to the lymph nodes, where it reproduces in T-lymphocytes [def] — also known as T cells — a type of white blood cell. As it continues to reproduce, the virus spreads to the lymph nodes throughout the body. This spread activates the cat’s immune system as it tries to fight off the virus. Both the spread and the immune response can result in temporary lymph node enlargement, fever, lethargy, and lack of appetite.

The above-mentioned symptoms, if an infected cat has them, can be mild enough and of a short enough duration that their human(s) don’t notice or don’t think they requires a vet visit.

Sources vary on when the acute phase starts, from 1-2 weeks after infection to 1-3 months after infection. The latter is listed in more of the sources, so I’m guessing it’s more accurate.

Latent

Once the initial, acute phase, illness passes, an infected cat will enter the latent, or asymptomatic, phase. This phase can last months or years; some cats will remain at this stage and never progress to the next phase. MY OPINION: I’m guessing that this is based on an individual cat’s body chemistry, the strain of the virus, and the length of their life. For example, if a cat has one of the less aggressive strains, is very healthy when infected, and is well cared for, then they could live an average life span without reaching the progressive stage.

During the latent phase, the virus continues to replicate in the host immune cells, spreading to the B-lymphocytes [def] — also known as B cells — as well. Infected cats may have some blood work abnormalities — especially low white cell levels or increased protein count — but will otherwise show no outward symptoms of illness related to FIV.

Progressive

Eventually, an infected cat will enter the progressive stage — so named for the progressive immune system decline — during which they become increasingly susceptible to infections and diseases. Technically, there are still little to no symptoms caused by FIV itself. Rather, most symptoms are caused by secondary infections or problems with the immune system. These can include:

• Persistent fever, especially fever of unknown origin
• Poor appetite and weight loss
• Fatigue
• Vomiting and diarrhea
• Coughing or sneezing
• Inflammation of the membrane around the eyes (chronic conjunctivitis), gums (gingivitis), mouth, lips, and/or intestines
• Severe skin conditions
• Difficulty breathing
• Severe dental disease and/or mouth ulcers or sores
• Recurrent illness including:
  • urinary tract infections.
  • upper respiratory tract infections.
• Autoimmune diseases
• Cancers, especially
  • lymphoma.
  • squamous cell carcinoma.
  • fibrosarcoma.
  • carcinoma.
• Neurological problems including weakness, seizures, or changes in behavior

The severity of the secondary illnesses can vary greatly, however, if an FIV positive cat becomes ill with multiple critical infections or cancers, survival time is usually no more than a few months. 

How is it diagnosed?

FIV is typically diagnosed through an initial blood test and can be confirmed, if necessary, with a second test. The various testing types used are enzyme-linked immunosorbent assay (ELISA) [def], western blot [def], immunofluorescence assay (IFA) [def], and polymerase chain reaction (PCR).

It is possible a cat will receive a false positive result:

• Kittens under 6 months old may have residual antibodies from their mother’s milk if she is FIV positive. If a kitten has a positive test result, it is recommended to retest when they are 6 months or older.
• If a cat was vaccinated against FIV, they will test positive on antibody tests, so an alternative test will be required.

A cat can also have a false negative test, as it can take two to four months for a cat to develop enough antibodies to be detected.

It’s important to know the FIV status of any cat before adoption, or to have any rescued stray or feral cat tested. If they have any risk of exposure (indoor/outdoor or outdoor cats) they should be rested regularly.

How is it transmitted?

In order for infection to occur, the live virus has to enter the bloodstream of the recipient cat. FIV is present in the saliva and blood of an infected cat. However, FIV is not able to survive for very long outside of living cells — generally no more than a few hours in most environments — making casual infection uncommon.

Bites

The main mode of FIV transmission is serious bite wounds from an infected cat. This is because infected cats mainly shed the virus in their saliva, which is then introduced to the bitten cat’s bloodstream. FIV is also easily spread through contact with FIV-positive blood, such as through a blood transfusion.

Pregnancy

An infected mother cat can transmit the infection to her kittens. This can happen during pregnancy, at birth, or soon after birth through infected milk. Some sources indicate that if the mother becomes infected with FIV during her pregnancy, the transmission risk to the kittens is increased as the mother will have a high viral load when giving birth.

Most sources indicate that mother-to-kitten transmission is rare, but I did find information that around a quarter to a third of kittens born to an infected mother are likely to be infected themselves. It is, of course, possible for some kittens in a litter to be infected while others are not.

Sexual contact

Unlike with HIV, sexual contact is not a significant means of spreading FIV among cats. However, how unlikely sexual transmission is considered to be varies from source to source.

Casual contact

FIV is not typically spread through casual, non-aggressive contact like sharing food and water bowls or litter boxes, mutual grooming, snuggling, and sneezing. This, however, does not mean transmission isn’t possible, and the risks should be considered before adopting an FIV-positive cat.

Other transmission

It’s not known whether blood-sucking parasites (e.g. fleas) can also spread infection. However, any cat with a risk of flea and tick infestation should be kept current on their flea and tick prevention.

How is it prevented?

The best form of prevention is keeping a cat indoors and away from other cats they may fight with. It is also important to keep an infected cat indoors to avoid spreading the infection.

Spaying or neutering a cat is also helpful for prevention as it can reduce a cat’s desire to roam and/or fight.

In a multi-cat household with both FIV-positive and FIV-negative cats, good hygiene and regular disinfecting can help reduce chance of transmission, as can having separate feeding bowls at regular mealtimes — rather than free feeding or sharing one or more large bowls.

How is it treated?

As mentioned above, FIV-infected cats can live happily with the virus for a long time, and, in some cats, the virus may never progress. However, once infected, a cat is infected for life.

At this time, there is no cure or treatment for FIV. Therefore, long-term care is focused on managing any other conditions or secondary infections that a cat might have and keeping them as healthy as possible for as long as possible. A veterinarian may suggest running additional diagnostic tests to get a better idea of the cat’s overall health and devise a management plan, which may change over time.

The better the general health of an FIV-positive cat, the longer the latent phase tends to be. To help keep a cat in top physical condition:

• Keep them indoors to reduce exposure to infectious agents 
• Feed them good quality, commercial cat food and avoid raw diets (due to increased risk of foodborne disease transmission) 
• Maintain routine preventive healthcare (vaccinations, etc.)
• Ensure they get sufficient exercise to maintain heart, skeletal, and muscular health
• Get them used to tooth brushing and brush their teeth daily
• Ensure twice-yearly veterinary health checks — some sources suggest checkups every four to six months
• Run additional blood tests or procedures as prescribed by their vet to help monitor their condition
• Monitor them closely for health and behavior changes to enable prompt diagnosis and appropriate treatment of any secondary or concurrent diseases 

Possible hope for the future

Some antiviral medications used to treat HIV also have some efficacy in treating FIV infection. However, the treatments that have been tested so far are complicated by side effects that can outweigh the — minimal, so far — benefits. Potential side effects include genital ulcers and sores, kidney damage, liver damage, decrease in blood cell production, cell death, and nerve damage. Despite this, continued research into antiviral medication could provide a breakthrough, as many available medications have not been tested against FIV.

What does it mean?

This question has many different answers.

Quality of life

Recent studies have shown that cats with FIV can live fairly average life spans, as long as they are not also infected with feline leukemia virus. One source mentioned a study found that on average, FIV-positive cats lived for 4.9 years after diagnosis compared to six years for uninfected cats.

Depending on the stage at which they are diagnosed and their continued care, cats with FIV can enjoy many healthy years after diagnosis. An FIV diagnosis in an otherwise healthy cat is not a medical emergency, although it could become one in the progressive phase.

FIV-positive households

For a household where the FIV-positive cat is the only cat, or where all cats are FIV positive, no additional care is necessary beyond that already mentioned above for an FIV-positive cat. FIV is a cat-only disease and cannot be transmitted to people, dogs, or any other kind of pet.

Mixed households

Managing a mixed household — one that includes FIV-positive and FIV-negative cats — seems to be a highly contested issue. Because the various sources provide such disparate information, on this topic, I’m going to provide what we’ll be doing with Floofenstein and our cats based on the research for this post. I recommend reading through some or all of the sources below to come to your own conclusions.

Jim and I understand that having an integrated household, rather than isolating Floofenstein or rehoming him, will carry some risk. However, we have plans to mitigate the risk as much as possible.

Assuming that everyone gets along well with Floof — there is no significant fighting — we will allow for a fully integrated life. To help with this, we will have Feliway diffusers to help keep everyone calm.

When it comes to the litter boxes, none of the sources mention any issue, so other than our typical monitoring for abnormal bowel movements, no extra changes are required.

Our cats already eat from individual automated feeders, so we don’t need to separate out food bowls. While Ritz, especially, will go from bowl to bowl looking for leftover crumbs, no one licks the dry food bowls, so there is minimal concern about inadvertent infection from salivary contamination.

Everyone gets wet food once a day, which we feed in separate bowls. This will continue, but Floofenstein’s bowl will be immediately removed once he’s finished eating, as will any bowl that he investigates for molecules. Because they lick the bowls clean, there is a greater risk of salivary contamination with the wet food bowls.

The water bowl is the most significant opportunity for salivary contamination — although it’s still fairly low. Ingesting contaminated saliva is less likely to cause infection than when infected saliva comes into contact with the blood stream through a bite. Because we cannot monitor our cats 24/7 to ensure that Floof is drinking from a completely separate water bowl, we will continue as is. We have a water fountain with two filters.

In short:

• Make sure everyone gets along. There can’t be any aggressive fighting — play fighting and wrestling is OK.
• No changes are necessary for litter box handling.
• Everyone gets their own dry food bowl. If one or more of your cats lick their dry food bowls, monitoring is suggested so you can immediately remove the bowls after meal times.
• Everyone gets their own wet food bowl. Ensure that the FIV-positive cat’s bowl is removed immediately, as well as any bowl they lick.
• Changes to a water bowl are dependent on what kind you have. Fountains are likely OK. Standing bowls should be cleaned and changed more frequently.

If your FIV-positive cat bonds with an FIV-negative cat, there may be issues with mutual grooming. You’ll have to speak to your vet about what best to do in that situation.

Related questions

Many of these questions have already been answered in the information above, but I want to provide direct answers to the questions I had in case it may be of use to others.

Do FIV-positive cats need additional vaccinations?

Yes and no. No in that — like with all cats — an FIV-positive cat must kept up to date on all recommended vaccinations. Yes in that it could be useful to also ensure that an FIV-positive cat has all indoor and outdoor cat vaccinations even though they are indoor only.

Should FIV-positive cats have more frequent vet appointments?

Yes. FIV-positive cats should have twice-yearly vet appointments, regardless of their age. Depending on their general condition, they may need to have thrice-yearly or quarterly appointments.

Do FIV-positive cats need to be in single-cat households?

As mentioned above sources vary wildly. I — and my vet — both agree that mixed households are perfectly acceptable. But, to show how disparate the information is, here are some direct quotes:

• Managing a household that includes FIV-positive and FIV-negative cats can get complicated. Ideally, the two groups would be completely separated, but if that isn’t possible and they don’t usually fight, giving them separate water and food bowls is about all you can do. | PetMD
• Cats in households with stable social structures where housemates do not fight are at little risk of acquiring FIV infections. | Cornell Feline Health Center
• Although FIV isn’t easily transmitted between cats (only through deep bites and not via sharing food and other normal interaction), the risk means that a FIV positive cat should only be adopted into a single-cat household. | Royal Society for the Prevention of Cruelty to Animals (RSPCA)
• As the risk of infection spreading to your other cats by social contact is low, you may choose to keep the FIV-positive cat with your other cats. In this case, the positive cat should have a separate feeding bowl from the other cats and food should not be left out for all cats to share. | VCA Animal Hospitals
• It is the sole responsibility of the adopter/guardian to make the decision to house an FIV+ cat with a non-infected cat. If done properly, they can lead happy lives together, but there is always a chance that if they fight the virus can be transmitted. | San Francisco Society for the Prevention of Cruelty to Animals (SFSPCA)

Is it OK for FIV-negative cats to share food and litter boxes with FIV-positive cats?

It is OK for mixed households to share litter boxes. However, to mitigate risk of spreading infection, FIV-negative and FIV-positive cats should not share food bowls.

Is there any extra concern if an FIV-positive cat breaks skin on a human?

I asked this question not out of concern about contracting FIV, but out of concern that they could be carriers for additional infection. However, according to my vet, the answer is no. There is no additional concern over the already-existing need to carefully clean and disinfect any wound from a cat.

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Sources

Alley Cat Allies ::: Feline Immunodeficiency Virus (FIV)

American/Canadian Pet Cancer Foundation :: Feline Immunodeficiency Virus and Transmission, How does FIV infection increase cancer risk?, Signs and symptoms of an FIV infection?, FIV diagnosis and treatment?

Cornell University College of Veterinary Medicine :: Cornell Feline Health Center :: Feline Immunodeficiency Virus (FIV)

Efficacy of Antiviral Drugs against Feline Immunodeficiency Virus

FIVCats.com :: Transmission

International Cat Care :: Feline Immunodeficiency Virus (FIV)

PetMD :: FIV in Cats

RSPCA :: Feline Immunodeficiency Virus (FIV)

SFSPCA :: FIV Information

VBSPCA :: Everything You Need to Know About FIV Positive Cats

VCA Animal Hospitals :: Feline Immunodeficiency Virus (FIV)

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Thanks for reading to the end, I hope you found this post useful. If you’re here because you have a cat with FIV, I hope they have many loving years with you and that you found some measure of comfort in the information I compiled.

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