Emergency veterinarians are often shocked that cat parents don’t know their cat’s “FIV” (Feline Immunodeficiency Virus) or “FeLV” (Feline Leukemia) status when they come into the ER. To vets, it’s the equivalent of not knowing if your partner has HIV or AIDS.
Why? Because FIV and FeLV are very contagious (to cats, not humans). And if you have another cat in your household, it risks and potentially shortens your other cat’s life. Both of these infectious diseases are common in cats and therefore warrant cat owners to be vigilant and intentional in trying to prevent their beloved felines from contracting them.
Vets recommend that any cat that you adopt, purchase, or rescue should always be tested for these two infectious diseases before you even let them see your other cats. This is important, so as to keep your other cats safe.
How are FIV and FeLV different?
FIV and FeLV have some very important differences. FIV is similar to HIV in humans in that it attacks and weakens the immune system. Feline Leukemia (FeLV) is much more devastating than FIV. This is because FeLV typically results in cancer, leukemia, and severe bone marrow suppression in young cats. The one commonality between FELV & FIV is that there is no cure for either.
Cats with FeLV only live for a few years. In contrast, cats can live with FIV for much longer (a decade or more), provided their other infections/inflammation of the body can be treated.
What it is: FIV vs FeLV
Feline Immunodeficiency Virus is a contagious virus that affects the immune system. The FIV virus spreads through the body and reproduces in white blood cells. It affects and spreads to the lymph nodes, and can rapidly progress. Similar to HIV, it makes a cat more at risk for getting infections and more immunosuppressed. Cats infected with FIV can lead a relatively long, normal life for years, but at some point, their immune system gets compromised and even the most common and innocent bacteria can cause serious disease and potentially death.
Feline Leukemia is a highly contagious and deadly retrovirus. FeLV affects a cat’s bone marrow and immune system and can result in cell mutation, cancer, and direct effects on the number of white and red blood cells in the body. This can result in leukemia and severe bone marrow suppression. As a result, a cat’s body is more susceptible to infections, parasites, inflammatory problems, and whole-body (or “systemic”) effects. The hardest part about Feline Leukemia is that it can manifest in so many ways: anemia, severe intestinal inflammation, neurological disease, and eye disease to name a few.
How it’s spread: FIV vs FeLV
FIV is species-specific and can spread to other cats if exchange of bodily fluids occurs, such as saliva, blood, sexual transmission, or placental transfer. The spread occurs most commonly through biting when territorial intact cats fight outside.
FeLV is also specific to cats. It is extremely contagious, especially from bite wounds or prolonged close contact with a FeLV+ cat. Cats get FeLV predominantly through bodily fluids such as saliva, milk, respiratory or nasal secretions, placental transfer, urine, blood, and, rarely, feces. Less common sources of exposure include using the same water and food bowls or the same litter boxes. It can also be spread through mutual cat grooming.
Symptoms: FIV vs FeLV
FIV sometimes has zero clinical signs and is diagnosed based on a routine blood test.
Both FIV and FeLV can present in the following ways:
- Lethargy
- Weakness
- Decreased appetite to complete inappetence
- Weight loss
- Unkempt, dull haircoat
- Recurrent fever
- Enlarged lymph nodes or swellings on the body
- Chronic gastrointestinal signs (e.g., diarrhea)
Symptoms more common to FIV include:
- Inflammation of the gums (e.g., gingivitis) and mouth (e.g., stomatitis) with secondary signs of halitosis, drooling, or chewing abnormally
- Chronic upper respiratory infections (e.g., runny eyes, sneezing, nasal discharge)
- Neurologic signs (e.g., behavioral changes, seizures)
- Chronic ocular infections (e.g., runny eyes, cloudy appearance to the inside of the eye, conjunctivitis or “pink eye”)
- Chronic skin problems (e.g., hair loss, thin coat, redness, itching, secondary bacterial infections)
- Urinary problems
Symptoms more common to FeLV include:
- Exercise intolerance
- Hypothermia (with severe symptoms, especially with anemia)
- Pale gums (e.g., anemia)
- Difficulty breathing
- Abnormal fluid in the chest cavity (e.g., pleural effusion)
- Tumors in the chest cavity (e.g., mediastinal tumors)
- Ocular changes (e.g., inflammation of the eye)
- Generalized infections or inflammation in the body
- Miscarriage or fetal death
- Death
Diagnosis: FIV vs FeLV
There are several blood tests for FIV and FeLV. The most common test done in veterinary clinics is an ELISA test, which automatically combines a blood test for FIV and FeLV. The FIV ELISA tests for antiviral antibodies, while the FeLV tests for the presence of FeLV or its antigens.
Kittens that test positive for FIV should be tested every 6 months for several years to confirm if they have FIV. This is because they may have been exposed to their mother’s FIV+ blood, but may “seroconvert” to FIV-negative several months to years later.
If a kitten or cat tests positive for FeLV, the veterinarian will need to send out different blood tests—the IFA or PCR—to confirm the diagnosis.
Treatment: FIV vs FeLV
There is no cure for FIV or FeLV.
Both FIV+ and FeLV+ cats should be kept indoors to minimize infections that they can get from outside, as well as to minimize spread of the disease.
If there are other cats in the house, FeLV+ cats MUST be kept separate. Ideally, FIV+ cats will be kept separate as well, but if all the cats in the house get along, an FIV+ cat can generally live among others without issue.
Treatment for FIV+ positive cats includes:
- Routine veterinary care, ideally 2x per year; this is important to help pick up on infections or problems as soon as possible, since your cat’s immune system is more vulnerable
- Preventive medication like deworming medication, heartworm medication, and flea and tick medication, as if they get infected, it will be harder for their body to fight it off
- Annual blood work to make sure the white and red blood cell count, kidney and liver function, protein levels, and salt balance are normal each year
Treatment for FeLV+ cats includes:
- Physical examinations 2-4x per year
- Preventative medication
- Blood work monitoring (to make sure they aren’t getting anemic or getting an infection)
- If you notice any clinical signs, seek veterinary attention immediately for treatment, since your cat will need more care for their weakened immune system
- Treatments for specific problems include antibiotics for an infection, fluids under the skin for dehydration, appetite stimulants for loss of appetite, and blood transfusions for anemia
Prognosis: FIV vs FeLV
As we mentioned earlier, FIV+ cats can live for years (a decade or longer)—but ultimately can succumb to death from secondary infection or even old age-related causes in cats.
Unfortunately, the prognosis for a cat with FeLV is poor. Most infected cats can only live for 2-3 years after the time of diagnosis, meaning cats rarely live past 5 years of age.
Most cats diagnosed with FeLV become symptomatic and die of FeLV-associated complications like anemia, infection, or cancer. Their body can’t contain or fight off the retrovirus, and the virus replicates aggressively in their lymphoid tissue and bone marrow. Once clinical signs of FeLV develop, the prognosis is grave, and vets often recommend humane euthanasia.
Prevention: FIV vs FeLV
The best way to prevent your cat from getting FIV or FeLV is by screening and testing all cats in your household at your veterinarian.
The next safest thing is to keep your cats indoors to prevent fighting with a stray neighborhood cat that may carry the disease.
While there is no vaccine for FIV, there is a FeLV vaccine. This vaccine is a must for all kittens, but it’s considered a non-core vaccine—in other words, not all adult cats need it as they age and mature. Keep in mind that the FeLV vaccine is not 100% protective. The best way of protecting your cat is also by minimizing exposure to FeLV-infected cats.
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