FeLV (Feline Leukemia Virus) and FIV (Feline Immunodeficiency Virus) are often confused because they are both retroviruses – in fact, they belong to the same retrovirus family. Both FeLV and FIV are, unfortunately, common infectious diseases in cats, so let’s explore the commonalities and differences…

Similarities of FIV & FeLV

As mentioned above, both of these diseases belong to the same retrovirus family. A retrovirus is a kind of virus that causes disease by inserting itself into the DNA of its host (your cat). Both of these retroviruses weaken a cat’s immune system, making them much more susceptible to secondary illnesses. Many cats with FIV or FeLV who pass over the rainbow bridge don’t actually pass from the disease itself, but from other infections or disease that attack the organs of the body because the defense system (immune system) is not able to fight any longer. That’s the bad news.

The good news is that there are ways to help support the immune system of FIV and FeLV positive cats – possibly avoiding secondary illnesses. There are plenty of cats that are able to live long and healthy lives with both of these viruses, when fed a high quality, well-balanced diet with added nutritional support.

Differences of FIV & FeLV

While FIV and FeLV are both in the same retrovirus family, they are certainly not exactly the same. They’re more like cousins than identical twins. FIV is a lentivirus – which is a slow-acting virus – and can take years to show symptoms. FeLV is a gamma-retrovirus – which is a faster-acting virus – but depends on the strain as to how quickly the symptoms will show.

Feline Leukemia Virus is highly contagious, whereas Feline Immunodeficiency Virus is usually only transmitted through severe bite wounds or from a milking mother.

FIV positive cats can usually live longer than FeLV positive kitties, because the virus isn’t as harsh when it rears its ugly head in the body. Unfortunately, FeLV commonly causes deadly diseases like cancer in cats. It is less common to see fatal diseases develop in FIV positive felines.


While both of these viruses sound scary and may make you want to turn your head to a possible rescue, don’t. It wasn’t their choice. They wouldn’t have chosen this disease – and they still need love and support just like the rest of us. Feeding a fully balanced and high quality diet, adding in nutritional supplementation and giving extra love can keep an FIV or FeLV positive cat around for many many happy, healthy years.


Recommended Product for FeLV Support


FeLeuk Kit for Cats



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