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FeLV Facts: Diagnosis and Transmission

Arnold Plotnick, D.V.M.

Recently, a seven-month-old kitten who had suddenly stopped eating was brought in to see me at the ASPCA Bergh Memorial Animal Hospital. Felix, a furry little black and white female, had been found a few months prior running around a dumpster in the back of a Manhattan supermarket. After some gentle coaxing, she was scooped up by her new owner, who decided that a kitten was just what her quiet studio apartment needed. She took Felix to a local veterinarian who gave her a thorough physical exam with all the usual vaccinations. Soon after, the kitten was spayed.

FeLV Facts: Diagnosis and Transmission


When Felix was presented to me some three weeks after her spay surgery, she was suffering from weakness, lethargy and a sudden loss of appetite. I noticed right away that her gums were pale whitea sure sign of severe anemia. But the rest of her examination was fairly unremarkable. I looked at Felix’s previous medical records and noticed that she was never tested for the feline leukemia virus (FeLV). I found it disheartening that a veterinarian would examine a kitten taken from the street and vaccinate and spay her without first making sure she didn’t have this deadly virus. So the first thing I did was run a FeLV test on Felix. I obtained a small amount of blood from her leg and ran the test in-house. Ten minutes later, my worst fear was realized: Felix had tested positive.

What is FeLV?
The feline leukemia virus is one of the most serious infectious diseases that affects cats. It is caused by a retrovirus, which is able to incorporate its genetic material into the host’s DNA, allowing the virus to survive long-term in the victim. Once in the animal, the viral DNA can cause several problems, including the transformation of normal cells into malignant cancer cells. In Felix’s case, the virus was preventing her bone marrow from producing red blood cells and she became severely anemic as a result.

Young kittens are highly susceptible to FeLV infection and disease. Adult cats and kittens older than 16 weeks seem to be less prone to this disease and exhibit a natural strong resistance to it. Although some infected cats may live for many years, the course of the disease differs from animal to animal, depending on age, overall immunity and the specific strain of the infecting virus. Once a cat begins showing symptoms, treatment is often futile; cats often deteriorate rapidly and ultimately die from this disease.

Feline immunodeficiency virus (FIV) is a member of the same family of viruses. Its effect on cats is similar to the feline leukemia virus, though often less deadly. A positive FIV test result in a kitten means that the kitten may be infected or, more likely, her mother is infected (the kitten gets her antibodies from her mother via the milk). A retest is recommended when the kitten reaches six months of age.

How Safe is Your Cat?
In a 2001 report, Feline Retrovirus Testing and Management, the American Association of Feline Practitioners and the Academy of Feline Medicine Advisory Panel listed the circumstances under which cats should be tested for the feline leukemia virus. The report states that testing should be done when cats are about to be adopted, regardless of age. It is especially important if the adopted cat is to be introduced into a multiple-cat household to prevent exposing resident cats to the virus.

Vaccination against the disease is recommended only for cats with lifestyles that place them at risk for exposure to the virus. Stray, outdoor and indoor/outdoor cats, as well as cats who may be exposed to other cats inflicted with the virus should be vaccinated. Indoor cats with no chance of exposure to other cats are unlikely to become infected. It’s important to note that the vaccine doesn’t fully protect against infectioncats at risk should be vaccinated as kittens, then given a booster shot three weeks later followed by an annual booster shot.

With no effective therapies and a grave prognosis for survival, I had no choice but to euthanize Felix before her condition worsened. The Bergh Memorial Animal Hospital of the ASPCA follows the guidelines set forth by the advisory panel. All cats adopted from our animal placement department are tested for the feline leukemia virus. A negative test is required before any cat is offered for adoption.

© 2002 ASPCA

ASPCA Animal Watch – Spring 2002

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