What in the world are FIV and FeLV?

Cats are said to have nine lives for a reason: they usually get into trouble and come out better on the other side.  With summer in full swing and kittens sprouting from the ground everywhere we look, there are lots of kittens and great adults looking to be adopted.  Most of these lovely felines come to us from living outdoors.  A few of these will come in with lifelong diseases.  None are good, but some are better to have than others.

FIV versus FeLV & How Does a Cat get it

cat7-COB-webFeline Immunodeficiency Virus (FIV) is one of the two most common retroviruses found in cats.  Now FIV might sound familiar and that is because it is in the same family as HIV (Human Immunodeficiency Virus).  There are two very important distinctions to deal with right off the bat.  First, you cannot get HIV from an FIV cat or FIV from an FIV cat.  Second, FIV does not behave exactly like HIV.  FIV is only found in about 1.5-3% of the worldwide cat population, which is slightly lower than the percentage we see in the shelter.  FIV is most commonly transmitted through saliva during fights between intact, male cats.  It can transmit through mating between a male and female, but infrequently.  Again, it is usually through an infected male biting a female.

Feline Leukemia Virus (FeLV) is the other retrovirus found in cats.  It is similar to FIV, but is a much more serious.  As the name implies, it can easily cause leukemia, a cancer of the white blood cells. FeLV is spread much more easily than FIV.  It can be spread in salvia, urine, feces, blood, and/or mother’s milk.  Again, the higher percentage of cats that contract the virus are intact male cats, but it has a higher chance of being given to kittens by an infected mother.

Signs of FIV and FeLV

Symptoms of FIV can take awhile to display in an infected cat.  After initial contraction, the cat can sometimes have a fever, lethargy, and loss of appetite for a few days.  Initially, the virus will take over a large portion of a white blood cells called T-lymphocytes.  Once the body detects the virus, it starts to make antibodies (a blood protein that fights off infection in humans and in pets).  Like HIV, the cat can never fully get rid of the virus.  In the large majority of cats they don’t have symptoms of the disease for years.  The most common findings are increased chance of getting sick (such as upper respiratory illnesses), GI upset, and having poor dental health.  Usually these cats live long lives with proper and loving care, including regular veterinary visits.


FeLV is a similar story.  Many infected cat will look fine and then quickly go into the end stage of disease (called a progressive infection).  The virus travels through the body over the course of initial infection until about 6-8 weeks.  From there it becomes quite complicated.  The cat can clear the virus altogether and no longer have the disease (a regressive infection) or it can linger in the body for weeks/months (discordant infection) or years (latent infection).  Many end up with the progressive infection, when the virus goes unchecked and causes catastrophic damage to the body.  The signs are usually a very poor body condition and cats are consistently sick even with treatment.  Blood work will show very low white blood cells and even low red blood cells.  Discordant and latent infections can become progressive, but regressive infections cannot.

Diagnosis of FIV and FeLV

Both viruses can be initially screened by most general practitioners and shelters with a SNAP test.  There is a difference though, as the FIV test looks for the antibodies produced by the cat, while the FeLV test looks for the parts of the actual virus.  This is important as some cats are vaccinated for FIV, which will always show up positive on a test even if they don’t have an infection.  If an FeLV test is positive, it means the cat has the infection or at minimum has been exposed.  For any cat that has a positive test at the shelter, we always send out to an outside laboratory for confirmation.  With FeLV, we can do further testing to try and categorize the cat into one of the stages mentioned.  This can be done with an IFA test that looks to see if the cells are actually infected or a RT-PCR test that is more sensitive than a SNAP test.  The only reliable test for FIV is the SNAP test and unfortunately there is no test to determine if a cat has been vaccinated or not.

Treatment & Prevention

Kitten-COB-WebUnfortunately, there is no cure for FeLV or FIV.  These are lifelong diseases that have to be managed with supportive care and close quality-of-life monitoring.  Due to the aggressive nature of FeLV and public health concerns for other cats, confirmed FeLV cats are commonly humanely euthanized.  This is why prevention and vaccination is so very important.  We as a society can easily help drastically decrease the number infected by doing a few simple things.  Those are spaying and neutering our cats and community (feral) cats, testing new cats brought into your home or a shelter, and even vaccinating against these viruses.

The FeLV is not a core vaccine, but is a common recommendation from veterinarians if you have more than one cat or you are coming in contact with high risk cats.  These are commonly just given the first few years of life as most adult cats have a strong immunity against the virus once they’ve grown up.  The FIV vaccine is a more cautious recommendation.  As it shows up as a positive on a test, many can be misdiagnosed.  Also the effectiveness of the vaccine is not fully understood.


FIV and FeLV are serious diseases that have very real and sometimes deadly consequences. Protect your cats by making sure they are vaccinated and getting them tested throughout their life. Early detection is key to ensuring your cats live long and healthy lives. Get your cat tested today by contacting our Veterinary Care Center at (913) 742-7310.

“AAFP Feline Retrovirus Management Guidelines”. American Association of Feline Practitioners’. Journal of Feline Medicine and Surgery. 2008, Vol. 10.
“Overview of Feline Leukemia Virus and Related Diseases”. Merck Veterinary Manual. 12/2014. Web. 7/24/2016.
“Ten-Year Study Comparing Enzyme-Linked Immunosorbent Assay with the Immunofluorescent Antibody Test for Detection of Feline Leukemia Virus Infection in Cats”. JAVMA. 1991, Vol. 10.
“Feline Immunodeficiency Virus”. Cornell College of Veterinary Medicine. Web. 7/24/2016.
 “Feline Leukemia Virus”. Cornell College of Veterinary Medicine. Web. 7/24/2016.

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