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Feline Immunodeficiency Virus (FIV): Symptoms, Prevention, and More


Eirevet is a veterinarian specialized in canine and feline internal medicine who owns a small animal veterinary hospital in Ireland.

FIV: Some Background Information

Feline Immunodeficiency Virus (FIV) is a retrovirus that is closely related to the human HIV virus. However, it does not pose a risk to human health, as it is species-specific. The virus was first identified in the mid-1980s in California, but it quickly became apparent that it is found worldwide.

Different strains or 'clades' of the virus are recognised, and their prevalence varies internationally, with subtype A being the most common in the UK and Ireland, and subtype B being more common in the United States. This information is useful to bear in mind when we later discuss vaccination against the disease.

How Is FIV Transmitted?

Infected cats shed infectious FIV particles in bodily secretions, and experimental studies have documented infection through various routes. However, 'natural' infection usually only occurs through biting, with the infected saliva transmitting virus into the victim's bloodstream. Therefore, infection is most common in outdoor entire male cats, and other outdoor cats that become involved in aggressive disputes over territory or other 'assets'. The lower risk of FIV infection is one of many reasons why it is advisable to have your cat neutered.

Although only around 1 in 25 cats (on average) in any given population are infected with FIV, it has been shown that around 1 in 6 cats that have suffered a cat bite wound will subsequently test positive.

Structure of a Retrovirus

How Does FIV Cause Illness?

Following infection, the virus is attacked by cells of the immune system. However, rather than overcoming the infection, these cells become the hosts for the FIV virus. It replicates in a particular type of cell called a T-lymphocyte, which is responsible for regulating the immune system. These T-lymphocytes are found throughout the body, and during the first few weeks of infection, lymph node enlargement may be detectable. The lymph nodes are structures containing large numbers of lymphocytes, which are found at various locations including under the jaw, in front of the shoulder joints, and between the bellies of the calf muscles in the hind legs.

The infected cat may display mild signs of illness during this phase, ranging from fever to inappetence, or signs may not be noticed at all. The vast majority of cats will then experience a very long asymptomatic phase while the virus 'quietly' resides in its host cells. However, even during this 'asymptomatic' phase, immune function is declining as the virus has a negative effect on the infected T-lymphocytes.

Many FIV-infected cats will leave reasonably healthy lives for years before developing signs of severe immunodeficiency. However, they will often require more aggressive treatment of minor illnesses, for example prolonged antibiotic courses, for relatively minor ailments in the interim.

FIV Blood Test Kit

Symptoms of FIV Infection in Cats

Most of the signs seen are not caused directly by the FIV virus, but are rather the result of a malfunctioning immune system. Immunity in a healthy animal is a careful balance between tolerance of non-harmful agents such as the animal's own cells, and recognition & elimination of harmful agents (pathogens). Because of the multiple roles T-lymphocytes normally play, illness in FIV can result from either a loss of tolerance, or a failure to effectively recognize and eliminate infectious organisms or cancerous cells.

While testing specifically for the virus using a kit such as that shown above is a very sensitive way of detecting infection, other findings on routine blood and other screens are non-specific and will not yield a diagnosis, so it is vital your veterinarian is suspicious of FIV in any cat with an unusually severe or recurrent form of any illness.

Gingivitis/stomatitis, a common condition causing severe mouth pain, is commonly seen in conjunction with FIV. It should also be ruled out in any cat with chronic rhinitis or flu symptoms. Unexplained weight loss or lymph node enlargement may also be seen.

Changes in behavior, seizures, and disrupted sleep patterns are common neurological symptoms, and FIV infection is also a cause of sterility in breeding animals.

Preventing FIV: Vaccination

While an FIV vaccine has been available in many parts of the world for some time now, it remains the subject of some controversy in veterinary circles for a couple of reasons. The vaccine is reasonably effective, preventing infection in about 4 out of 5 vaccinated cats that are exposed to the same subtype of the virus, and this is part of the problem; while the vaccine protects against the majority of strains found in North American cats, it is ineffective against strains found in Europe. For this and other reasons, the vaccine is not licensed for use in European countries.

The other issue with the vaccine is that it can lead to difficulties in assessing whether an animal is infected or not later in life. Even in a vaccinated cat, there is still a chance that he/she can become infected later in life. FIV blood tests performed by veterinarians measure antibody levels against the virus, and at present there is no reliable way to distinguish between an animal that has high antibody levels due to vaccination and one which has been infected by the FIV virus.

The situation is even more difficult when dealing with a stray cat that is being taken in by a rescue organisation or an individual, for in these situations we would like to test the incoming cat for infectious diseases. If the cat tests positive for FIV we have to consider the possibility that this was a previously owned pet who was vaccinated against FIV, and we are now unsure as to his/her FIV status. A real conundrum, and one to which we don't yet have a solution.

Your Relationship With Your Veterinarian

If you have an FIV-positive cat, you are both certainly going to rely on a lot of input from your veterinarian over the years. I am strongly of the opinion that if your vet does not have a positive outlook about managing your cat's health, or indeed advises that you euthanize your cat at the time of diagnosis despite your cat being otherwise in good health you should find a new vet.

Your Cat Is FIV Positive: What Now?

FIV is NOT a death sentence. While the FIV virus itself is resistant to treatment, the illnesses caused by the immune deficiency are not. It is important your veterinarian knows the FIV status of your cat in order to formulate appropriate treatment plans, which generally need to be more intensive and more prolonged than those in an FIV negative patient with similar symptoms. However, an FIV positive status must never be used as a reason not to pursue diagnostic investigations or treatments.

There have been several 'false dawns' in the pursuit of antiviral treatments effective against FIV. While there have been some published reports of effective treatment of the virus with human anti-retroviral drugs (eg AZT) used in the treatment of HIV and AIDS, any antiviral benefit is outweighed by negative effects on the patient such as anemia. In any case, with careful management of any secondary problems such as gingivitis or chronic flu symptoms, most FIV-positive cats can enjoy a good quality of life for almost as long as an FIV-negative patient.

Where to Find a Good Cat Veterinarian

  • AAFP | American Association of Feline Practitioners
    If your veterinarian is not positive or proactive about managing your FIV positive cat, then this is a useful resource to locate a cat-friendly veterinary practice.

Quality of Care for Cats With FIV

Routine Health Care of Cats With FIV Infection

As well as being susceptible to viral and bacterial infections, your cat is more likely to develop heavy burdens of parasites, even with a lower level of exposure. Hands, feet and clothing can easily carry fleas or worm eggs or larvae from outdoors, and regular deworming and flea treatments are essential.

Cats with FIV should never be fed raw meat as they are much more likely to suffer acute food poisoning, or infection with toxoplasma which can lead to serious illness or death. A balanced, good quality commercial cat food is the best diet for most cats, but especially those with immunodeficiency.

Vaccinations for FIV Positive Cats

While there has been some controversy about vaccinating an FIV-positive cat against the common diseases, notably the flu viruses and panleukopenia virus, FIV-positive cats that are generally well do respond well to vaccination. They show appropriate increases in antibody levels after vaccination which are protective against these illnesses.

However, there is a possibility that vaccination may promote viral replication through T-lymphocyte stimulation. This seems to be a theoretical concern which has not been borne out through research to my knowledge, so in general most feline practitioners would recommend vaccination except in exceptional circumstances where the owner can guarantee that neither they nor their cats will be in contact with other cats.

The most common route for the spread of most feline viral diseases is not direct contact between cats, but rather on fomites such as hands and clothing. Speak to your veterinarian to assess your cat's individual risk of contracting disease.

Be a Responsible Owner

Unfortunately, you need to consider your FIV positive cat a risk to other cats. FIV is essentially a disease passed on through aggressive behavior, and as such there is a low risk of transmission between cats in a 'stable' household with the introduction of no new pets, and no major upheavals (eg moving home, having an elderly relative moving in). In the event of a major stress within the house, tempers may flare, and inter-cat aggression may become a problem.

Should I Separate My FIV-Positive Cat?

However, I do not usually advise my clients to separate their FIV-positive cats from the negative ones within the house. If a stress such as those mentioned above can be anticipated, then taking steps such as using Feliway to reduce aggression are advisable.

Of course, as well as the risk from your cat, your FIV-positive kitty is also more susceptible to contracting other illnesses from cats outdoors. This risk is also obviously eliminated by preventing his/her contact with cats of unknown health status.

Should I Let My FIV-Positive Cat Outside?

While the risk to the other cats in your home may be very low, the same cannot be said for other cats your pet encounters outdoors. Territorial aggression is very likely to result in biting behavior, and even a relatively passive cat could potentially find themselves in a situation where they bite another animal, and thereby pass on this incurable illness.

For this reason, the only responsible way to manage your cat with FIV is to make him/her an indoor-only cat. This may be a huge challenge, but one cannot knowingly put somebody else's beloved pet at risk of contracting a long-term illness.

If your cat has been used to having outdoor access, then it is vital that you try to replace some of the stimulation which outdoor living provides within the confines of your home. Climbing trees, laser pointers, and robotic mice are just a few of the things you can provide to make your home more stimulating and cat-friendly.

What Does It All Mean?

If you take nothing else from this article, I do want to convey that FIV is not a terminal illness. I have had more than one patient with FIV infection that lived beyond twenty years of age. With dedication from the owner, plenty of input from a committed veterinarian, an enriched environment, and good quality nutrition, your cat can live a long, healthy, and happy life.

Please use the comments section below if you would like to leave a message or have any questions regarding your cat.

Want to Know More? A Detailed Presentation on FIV

© 2015 eirevet

Sharon Licon on April 16, 2019:

Im so glad I read these articles on FIV. My 11yr.old cat Fluffy tested positive for it. Ive been so afraid for my other cats that I havent wanted them to be anywhere near him or drink out of the same water dish. My vet said it wasnt contagous, but didnt explain how it spreads. Now I know more and am feeling so much better.


How Is FIV Diagnosed And What Are The Symptoms?

FIV is usually diagnosed through blood tests. These tests are designed to highlight any antibodies and need to be carried out by a vet.

Unfortunately, cats might not show symptoms for a number of years after any initial infection. But some common symptoms to look out for include:

  • weight loss
  • lowered appetite
  • pain while chewing
  • fever
  • larger than usual lymph nodes
  • diarrhea
  • eye or nose discharge
  • skin, bladder, or kidney infections
  • seizures
  • sleep disorders

These symptoms can appear with other conditions, too. If in doubt, consult your vet.


10 Symptoms Of Feline Immunodeficiency Virus (FIV)

Feline Immunodeficiency Virus, or FIV, is a slow-acting virus very similar to HIV in people. Although it might take years for symptoms to present in a cat with FIV, they do have suppressed immune systems and will be much more susceptible to infections and other ailments. If you notice any of these symptoms in your cat, be sure to seek veterinary attention.

#1 – Weight Loss

Just like people, cats with long-term illnesses such as FIV will have trouble maintaining their weight regardless of how much food they eat. If you’ve noticed rapid weight loss or unplanned weight loss, be sure to check with your veterinarian.

#2 – Conjunctivitis

Although many cats will suffer conjunctivitis once or twice in their lives, cats with FIV are much more susceptible to small infections.This means that chronic eye infections are relatively common and are typically a sign that something more serious is going on.

#3 – Enlarged Lymph Nodes

Feline Immunodeficiency Virus is a viral infection and leads to enlarged lymph nodes throughout the body. If you notice any swelling on any or all of them, be sure to take your cat to the veterinarian immediately.

#4 – Dental Disease

Dental disease is more common in cats with FIV because they’re at a higher risk for infections. Even if you keep your cat’s mouth clean and brushed, you might notice that dental disease happens anyway.

#5 – Discharge from Eyes & Nose

Nasal and optical discharge is common in cats infected with FIV. Even if Feline Immunodeficiency Virus isn’t the cause of the discharge, a respiratory infection may be the culprit and your cat will need veterinary care.

#6 – Sneezing

FIV puts cats at a higher risk for all infections, including respiratory ones. Sneezing could very well be a cause that something is awry, especially if it’s become chronic. Be sure to make an appointment with your veterinarian to ensure the cause of this sneezing gets under control.

#7 – Non-Healing Wounds

Cats infected with FIV have very weakened immune systems and you might notice that they’re unable to heal any wounds effectively. Even small scrapes and scratches can become infected and get worse very quickly. If you notice your cat has a wound that isn’t healing, be sure to see a veterinarian as soon as possible.

#8 – Poor Appetite

It’s very common for cats that don’t feel well to turn away from food. Because not eating can be very dangerous to cats even if only skipping one or two meals, it’s important to seek veterinary care to ensure your feline gets adequate nutrition.

#9 – Poor Coat Condition

Your cat’s coat condition will tell you a lot about his general health and keeping an eye on it is important. Cats with FIV often have very poor coat conditions even with regular grooming by both the cat and you. If you notice you’re unable to keep your cat’s coat looking well kept, be sure to make an appointment with your veterinarian.

#10 – Fever

Fever is one of the main symptoms of any infection and it almost always presents in cats that have FIV. If you think your cat has a fever, you should take her to the vet as soon as possible. Even a minor infection can become a big problem.


What Is FIV in Cats?

If you're a cat parent, you may have heard of FIV, but what is it? FIV is short for feline immunodeficiency virus, which is an infectious retroviral disease in cats. FIV is a lot like HIV in humans: It attacks a cat's immune system, weakening it over time and leaving them vulnerable to secondary infections. Once a cat is infected with FIV, they're infected for life.

Keep reading to learn more about FIV, including its signs, how to prevent the virus in your cat and how FIV treatment works.


How Is FIV Treated?

Once infected with the feline immunodeficiency virus, there is no way to eliminate the virus from a cat's body.   Cats that are sick from FIV are treated symptomatically. For example, if secondary bacterial infection is present, antibiotics may be necessary. The treatment will vary depending on the signs being seen.

Drugs that strengthen the immune system are often used and are not harmful. Anti-viral drugs (drugs that fight viruses) are also sometimes used and also do not appear to be harmful. However, it is not known whether any of these drugs actually help infected cats.  

The most commonly used drugs include:

It is important to remember that a positive test for FIV in a cat does not equate to a death sentence. Cats with positive tests for feline immunodeficiency virus that are healthy and free of signs of disease can live perfectly normal lives for an extended period of time.  


Watch the video: FIV- Feline Immunodeficiency Virus Cats Disease (July 2021).