Tales from the Pet Clinic

By Ann Hohenhaus

This is the fourth in a series of blogs about fabulous felines written for “Adopt-A-Cat Month.”

Thankfully, veterinarians don’t have to talk as much as they used to about feline leukemia virus (FeLV). Prior to the introduction of universal testing and vaccination against the virus, we cared for cats infected with FeLV on a daily basis. Depending on the variety of the virus, we saw young cats suffering from lymphoma of the thymus or anemia due to bone marrow suppression. Today, most cat owners have their kittens tested at the first kitten check-up or kittens come from the shelter already tested. Cats with free access to the outdoors are at risk for contracting the virus since the virus is spread via contact with an infected cat. The virus gives cat owners another good reason to keep their cats safe by keeping them indoors.

Correcting confusion

Feline leukemia virus infection is not synonymous with leukemia, a cancer of the bone marrow. Feline leukemia virus is a viral infection with similarities to the AIDS virus. Sometimes FeLV coexists with a diagnosis of cancer of the bone marrow, but not as often as it did prior to universal testing and vaccine development. Both diseases—FeLV infection and cancer of the bone marrow—are serious, life-threatening disorders. Only feline leukemia virus is completely preventable by keeping your uninfected cat indoors.

Ubiquitous virus

Feline leukemia virus can be found worldwide, with recent reports of the virus in Malaysia, Egypt, northern and southern Europe, and Iran. Even the cats of island nations are not spared, as the virus can be found in felines of the West Indies, Japan, and Australia. The occurrence of FeLV in the United States varies; it occurs more frequently where cats are allowed to roam freely outdoors and ranges from one to five percent of cats tested.

Not just your domestic cat

The cat currently sleeping on your computer is not the only type of cat that can contract FeLV. Wild cats are also at risk, with reports of the virus in the Florida puma, Iberian lynx, cheetah, ocelot, and the wild felids of Brazil. Another reason to keep your cat indoors is to prevent spread of the virus to wild felines. Infection with FeLV adds survival pressure to wild feline species already endangered by reduction of their natural habitats resulting from global warming and urbanization.

Common co-infections

Feline leukemia virus infection increases the occurrence of other infections: feline immunodeficiency virus, toxoplasmosis, and heartworms. The exact cause is unknown, but possibly outdoor cats are exposed to more infectious agents or FeLV may pave the way for a second infection through suppression of a cat’s natural immune defenses.

To find the prevalence of FeLV infection in your area, as well as other infections check out the parasite prevalence maps.