FeLV:

Approximately 2%-3% of all cats are infected with this virus… but this virus can evolve into the leading cause of cancer in cats.

 

What is feline leukemia virus?

FeLV or Feline leukemia virus, is a retrovirus. All retroviruses, including feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV), produce an enzyme, reverse transcriptase, which permits them to insert copies of their own genetic material into that of the cells they have infected.

How common is the infection? 

FeLV-infected cats are found worldwide, but the prevalence of infection varies greatly depending on their age, health, environment, and lifestyle. In the United States, approximately 2 to 3% of all cats are infected with FeLV. Cats living with infected cats or with cats of unknown infection status, cats allowed outdoors unsupervised, where they may be bitten by an infected cat, or kittens born to infected mothers are all at high risk for contraction of the disease.

How is FeLV spread? 

Cats persistently infected with FeLV serve as sources of infection. Virus is shed in very high quantities in saliva and nasal secretions, but also in urine, feces, and milk from infected cats. Cat-to-cat transfer of virus may occur from a bite wound, during mutual grooming, and (though rarely) through the shared use of litter boxes and feeding dishes. Transmission can also take place from an infected mother cat to her kittens, either before they are born or while they are nursing.

What does FeLV do to a cat?

Feline leukemia virus adversely affects the cat's body in many ways. It is the most common cause of cancer in cats, it may cause various blood disorders, and it may lead to a state of immune deficiency that hinders the cat's ability to protect itself against other infections. The same bacteria, viruses, protozoa, and fungi that may be found in the everyday environment—where they usually do not affect healthy animals—can cause severe illness in those with weakened immune systems.

What are the signs of disease caused by FeLV? 

During the early stages of infection, it is common for cats to exhibit no signs of disease at all. However, over time—weeks, months, or even years—the cat's health may progressively deteriorate or be characterized by recurrent illness interspersed with periods of relative health.

Testing for FeLV and FIV can be done in hospital and results can be received quickly.  It is a simple blood test.  All cats should be tested at some point, it is most ideal for all kittens to be tested.

Prevention of the disease is to keep your pet aware from the risks (keeping the indoors or away from infected cats).  There is also a vaccine available, this is for cats that are outdoors.