Introduction
There are three types of feline leukemia viruses (FeLV), and all of these viruses are a type of retrovirus. How an infected cat is affected by the virus depends on what type of strains the cat is carrying. The three types of feline leukemia viruses are FeLV-A, FeLV-B, and FeLV-C.
Types of Feline Leukemia Virus
FeLV-A is found in all cats infected with feline leukemia. This is the form of the virus that is used for making feline leukemia virus vaccinations. FeLV-B occurs in about 50% of the cats infected with FeLV-A. This form of the virus occurs when FeLV-A virus combines with DNA from FeLV already present in the cat’s system. Type FeLV-C is only found in about 1% of all the cats affected with FeLV-A, and it is considered to be quite rare. This from of feline leukemia occurs when an original FeLV-A virus in the cat’s system mutates.
FeLV-A is the type of feline leukemia that causes wide spread suppression of the cat’s immune system. The virus will eventually weaken the cat’s immune system to the point where secondary invaders start to infect the cat. FeLV-B causes cats already infected with FeLV-A to experience symptoms which involve excessive or abnormal tissue growth and tumors. FeLV-C causes cats with FeLV-A to develop serious and life-threatening anemia.
While there are three types of feline leukemia, a cat cannot become infected with FeLV-B or FeLV-C if it is not already infected with FeLV-A. This means that a cat can carry two forms of the virus at the same time; in very rare cases cats can carry all three forms of feline leukemia viruses.