Feline immunodeficiency virus or feline AIDS as it's often called. It's caused by the same family of viruses that cause AIDS in humans with the same resulting illness and death. It's transferred through blood and saliva and is mostly contracted by cats fighting. Some 10-20% of cats have the virus.
So we have the same virus with the same health effects in cats but we don't call it a gay cat disease, even though pets do occassionally hump the same sex or inappropriate objects? It's more like a macho fighting disease with cats. If humans got AIDS from fighting each other we might be forced to get along more, spend more time being lovers, gay or straight, without the current prejudice I hope? At least we don't hump stuffed animals and pillows?