Feline leukemia virus is a highly fatal disease causing a variety of malignancies, immunosuppression and anemia. It is found most commonly in outdoor male cats one to six years old, but any cat is potentially at risk (Nelson & Couto, 1999).
There are three strains of feline leukemia virus. All cats are infected with the first strain, FeLv A. FeLv B and C both develop from FelV A, so it is possible for cats to be infected with more then one strain, or even all three (Merck and CO., Inc, 2008).
Feline leukemia is transmitted by prolonged exposure to infected cats’ secretions such as saliva and nasal discharge. Often this occurs as a result of grooming, or sharing food and water dishes. The virus can also be passed from a queen to her kittens through milk, or the placenta, though this is more rare. Once a cat has been exposed to feline leukemia virus, the virus replicates in the cat’s oropharanx. From there it is carried by blood cells to the spleen, lymphnodes, epithelial cells in the intestines and bladder, salivary glands, and bone marrow (Merck and CO., Inc, 2008).
According to The Merck Veterinary Manual, 70% of adult cats will develop a transient infection, meaning that the cat develops antibodies and fights off the virus. A few of the above cats will however, become carriers of the virus in their bone marrow, spleen, lymph nodes, and small intestines (Nelson & Couto, 1999). These cats won’t show any symptoms of infection until the virus is activated by stress, or other conditions. The virus can also be activated by certain steroids, called glucocorticoids, or other drugs that suppress the immune system. Examples of glucocorticoids include many commonly used drugs such as: dexamethasone, hydrocortisone, prednisone, and prednisolone. The remaining percent of cats won’t be able to mount an adequate immune response to the disease and will generally die within 2-3 years (Nelson & Couto, 1999).
How Feline Leukemia Affects Cats
Cats with feline leukemia virus often present to their regular vet with symptoms that are non specific. These include: anorexia, weight loss, and depression (Nelson & Couto, 1999).
Feline leukemia virus causes a variety of malignancies in cats. The Merck Veterinary Manual estimates that up to thirty percent of FeLv cats will develop some for of cancer. Small Animal Internal Medicine states that 96 % of these cats have either lymphoma or leukemia.
Leukemia virus also suppresses the immune system, making the cat more susceptible to infections. This is believed to be a result of high levels of antigen in the blood, which interfere with the body’s ability to fight off infections. In addition, it also can also cause several immune-mediated diseases such as polyarthritis. Immune-mediated illnesses occur when the immune system over reacts and starts attacking the cat’s body.
Prevention
It is very important to prevent the spread of feline leukemia virus to other cats. The Merck Veterinary Manual recommends testing all new kittens and adults cats prior to entering the household. Also consider keeping all cats indoors. There is a vaccine for FeLv, but it is not 100% effective, and has been known to cause sarcomas at the injection site. Because of this, it is recommended that only at risk cats be vaccinated. It is important to keep infected cats indoor all the time and away from other cats. If there are multiple cats in the home, all uninfected cats should be vaccinated for feline leukemia virus. It is still very important to keep them separated however, because constant exposure is likely to result in infection, even if the cat is vaccinated (Merck and CO., Inc, 2008).
For information on the diagnosis and treatment of feline leukemia read: Diagnosis and Treatment of Feline Leukemia Virus
Works Cited
Merck and CO., Inc. (2008). Feline Leukemia Virus and Related Diseases: Introduction. Retrieved October 16, 2008, from The Merck Veterinary Manual: www.merckvetmanual.com(1999).
Feline Leukemia Virus. In R. C. Nelson, & G. C. Couto, Small Animal Internal Medicine (pp. 817-821). St. Louis: Mobsy, Inc.
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