Feline Leukemia (Felv)/Feline Immunodeficiency Virus (FIV)

Feline leukemia (Felv) is a deadly disease. Dr. William Hardy first isolated this contagious viral disease in the early 1970’s. It was not until the mid 1980’s that the first vaccine against Felv was produced. Subsequently, a second virus called Feline Immunodeficiency Virus (FIV) was isolated as a distinct entity. At present there is still no vaccine available to protect against the FIV infection. Both viruses have been studied because of their similarity to the Human Immunodeficiency Virus condition. Neither virus is considered to be transmissible to man.

The Felv virus is spread by contact with bodily fluids, such as saliva and urine, from an infected cat. The FIV disease is spread only by a bite from an infected cat. Up to 40% of the cats exposed to Felv may recover on their own. We don’t know if any of the cats infected with FIV can recover. If your cat has been infected at an early age to Felv he/she will almost surely die within three years. We really don’t know, however, how soon after being infected with FIV a cat will die, if at all. If your cat has been infected with Felv as an adult or later in life, there is a reasonable chance that he/she may live as a carrier for many many years. In the state of Connecticut the incidence of Felv has been reported to be as high as 12% of the cat population while it has been as high as 9% for FIV.

Symptoms of Felv may vary considerably depending on the age and the genetic makeup of the individual cat. Some of the most common symptoms in the young cat are a fluid build up in the chest, an enlargement of the thymus gland, anemia, followed by a rapid general decline. In the adult, similar signs may be expressed, as well as periodontal disease, liver disease, diarrhea, lymphosarcoma, spinal disease and chronic debilitation. Symptoms of FIV infected cats appear to be expressed as any form of chronic illness.

There has been some progress in the treatment of the Felv infected cats. Colorado State University has reported as high as an 80% success rate with bone marrow transplants. Considerable amount of research is being conducted at Cornell University, Angel Memorial Hospital in Boston and through the Morris Animal Foundation. Chemotherapy, however, has been tried with disappointing results.

Both Felv and FIV are outdoor, cat-to-cat diseases and thus 100% indoor cats are at little if any risk. The older cat that lives mostly outdoors is the most likely to have either the Felv or FIV or both diseases. The blood test to confirm the diagnosis of either of these diseases is based on the antigen-antibody reaction that is produced when the natural disease is present. If your cat leads an indoor-outdoor or mostly outdoor lifestyle then testing every couple years for FIV is appropriate even if your cat is vaccinated against Felv.

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