What Causes Feline Leukemia?

Feline Leukemia is a misnomer, because this is a disease that is borne by a retroviral infection, which is now known as the Feline Leukemia Virus or FeLV. Although it causes many symptoms and disorders that are like those of Leukemia, it is not always considered as a form of cancer.

A retrovirus like those of the feline immunodeficiency virus (FIV) and the human immunodeficiency virus (HIV, which causes AIDS) have the uncanny ability of being able to enter into their host’s cells and infuse it with their own genetic material. To do this, the retrovirus produces an enzyme, which is a reverse transcriptase or an RNA dependent DNA polymerase. In layman terms, the retrovirus makes a copy of its RNA genome and transcribes it into DNA. The process is usually the other way around, with the DNA creating the RNA, and DNA is usually produced using another DNA strand as its template.

The danger that the retrovirus brings, aside from the blood disorders that can afflict the cat is that it opens the feline to “opportunistic” infections, which means that the common fungi, bacteria, and other microorganisms that are harmless to healthy cats can be life threatening to an FeLV infected cat.

The only way a cat can get the virus is from another cat. Like most retroviruses, FeLV is transferred through bodily fluids and secretions. That includes blood, saliva, feces, urine, and nasal secretions. But if an infected cat shares the same feeding bowl with an uninfected cat, there is a slight chance of transfer. It is usually through bites and mutual grooming that the virus is transferred from one cat to another.

The retrovirus has a very short survival period outside the infected cat’s body if it should land on a dry surface, like the floor or on dry sand. In such climates, it will survive and be infectious for a few hours at the most. But, if it finds a damp surface, like a dirty litter box, the retrovirus can survive for up to 48 hours.

Not all cats that are exposed to the virus will get infected: some of the exposed cats have the immunity to fight it off, and can become immune to the disease. Even when that happens, the healthy cat can still be a carrier and infect other cats.

Another way that a cat will get the FeLV virus is if it is born from an infected mother. In such cases, the infection is almost inevitable because not only does the mother share its blood during pregnancy, and milk after birth, kittens also do not have a strong enough immune system to fight off the virus. A kitten will have the immune system strong enough to be able to fight the infection somewhere around its eighth month of life.

Infection is higher in urbanized areas, because of the density of the cat population. More cats share the same “hunting” grounds and have greater chances of interacting with an infected cat.