Feline Leukemia Virus

Feline leukemia virus (FeLV), a retrovirus that infects cats, is transmitted between infected cats through saliva and nasal secretions. If the cat’s immune system does not take care of the disease then it can be lethal due to it being a cancer of blood cells called lymphocytes.

Symptoms can vary from loss of appetite, to poor coat condition, infections of the skin, bladder and respiratory tract, oral disease, seizures, lymphadenopathy, skin lesions, fatigue, fever, weight loss, stomatitis, gingivitis, litter box avoidance, poor grooming, anemia, diarrhea, and jaundice.

Infected cats further spread the infection through saliva, close contact, biting, litter box, and food dishes. FeLV survival time is unknown although thought to be short. It causes immuno-suppression in pet cats. Evidence suggests that FeLV is not transmissible to either humans or dogs. Strong evidence says that kittens under four months are susceptible but once they hit 8 months they are resistant. Kittens can be born with it if they contracted it in utero. City cats have a far higher infection rate compared to strays and rural cats.

It is also possible that an infected cat can survive the disease then become a healthy carrier. FeLV has four subgroups: A, B, C, and T. A is the only one transmissible between cats. Subgroups are defined based on viral interference and in virto host range. Around 40% of cats are able to overcome the virus while about twenty percent of those put the virus into a latent stage in which the virus will remain until the cat becomes stressed.

There are six phases of the virus. The first phase it enters the cat, then the blood stream, and eventually infects the lymphoid system. Phase four is the main point of the infection when damage is really done. If the immune system fails then the bone marrow gets infected and eventually the cat’s body is overwhelmed by infection. There is no known cure although there are vaccines that offer some protection. The vaccination has been known to cause some serious side effects including aggressive tumors at the injection site.

Merial has produced a vaccine that is thought to be safer than the old vaccine since it does not require an adjuvant to be effective. Since the virus dies within two hours in a dry environment keeping a litterbox dry between uses helps to slow transmission of the virus. Interferon omega is the only approved treatment for feline leukemia in Europe and lymphocyte t-cell immunomodulator in the United States. FeLV and Feline immunodeficiency virus are of the same family and commonly mistaken one for another. They are, however, different since FeLV is more circular while FIV is elongated. Their protein coats differ in size and composition and FeLV usually causes symptoms while FIV may be asymptomatic for a cat’s entire life.