Understanding feline retroviruses, including Feline Immunodeficiency Virus (FIV) and Feline Leukemia Virus (FeLV), is critical to the health of your cat population.
FIV is primarily transmitted through deep bite wounds, when the virus enters the bloodstream of the cat. Unsurprisingly, unneutered free-roaming toms, who are the most likely to fight over territory and mates, have the highest incidence.
In a study published in 2014, researchers followed a group of 130 FIV-negative cats and eight FIV-positive cats, all of whom were sterilized and mingled freely in a rescue environment. After several years, despite mutual grooming and “minor episodes of aggression,” none of the negative cats tested positive.
FeLV, which is found in the blood, saliva and other bodily fluids of an infected cat, is most commonly transmitted from an infected queen to her kittens. Healthy adult cats have partially protective natural immunity to the virus. However, there is a small risk of spread through casual contact, such as mutual grooming or sharing water and food bowls.
While there are plenty of anecdotal reports of noninfected cats cohabitating with FeLV-positive cats without contracting the virus, most experts recommend not mixing the two populations. It’s uncommon to transmit FeLV in sterilized adult cats. It takes prolonged intimate contact, and even then it’s uncommon. Cats housed next to each other in cages are not going to give FeLV to one another, even if they sneeze on the other.
Several studies show that FIV cats have comparable life spans to noninfected cats, but the answer for FeLV cats is more complicated.
The data so far indicates a significantly shorter than average life expectancy, but with tremendous variability among individual cats. Some cats who initially test positive will essentially buck off the infection and later test negative. Some, showing what’s called a “regressive” infection, will continue to test positive with low levels of virus but could remain healthy into their teens and 20s. Some will have a “progressive” infection and succumb to a virus-related illness at an early age. And some have test results that flip flop from month to month.