Nearly four decades ago, and shortly after the U.S. began to grapple with the AIDS epidemic among humans, two veterinarians working in a lab at the University of California, Davis, made a shocking discovery. When called to check on several cats that had come down with a mysterious illness, Dr. Niels Pedersen and Dr. Janet Yamamoto found that immunodeficiency viruses aren’t relegated to humans.
“I was confronted while in clinics with an outbreak of AIDS-like disease in a private shelter-type situation,” Pedersen told Straight Arrow News. “I decided to inject blood from one of these cats into the laboratory cats to see what would happen.”
Much to Pedersen’s and Yamamoto’s surprise, the cats developed enlarged lymph nodes and blood changes that resembled the initial stages of HIV/AIDS. They were then able to isolate a lentivirus –– the same family of viruses that underpins HIV/AIDS –– from the blood of the cats, “and the rest,” Pedersen said, “is history.”
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How is FIV transmitted?
According to Cornell University’s Feline Health Center, between 2.5% and 5% of healthy cats are infected with Feline Immunodeficiency Virus, or FIV. That rate jumps to around 15% of cats who are sick or at high risk of infection. The American Association of Feline Practitioners also suggests that infection rates could be as high as 1 in 12 cats, with about 25% of diagnoses in female cats and upwards of 75% in male cats.
Despite being colloquially known as “cat AIDS,” FIV only partially resembles HIV/AIDS in humans. For instance, the disease cannot be sexually transmitted between cats, and is rarely passed from a mother to her kittens.
“The placenta is a potent barrier between mother and fetus, and most kittens are not infected by their carrier mothers,” Pedersen explained. “The exception would be when they are conceived during a time when the levels of virus in the maternal blood and first milk are very high, i.e., during primary or late stages of infection.”
Rather, FIV is most commonly transmitted through deep bites, meaning outdoor cats prone to fighting are particularly susceptible. “We estimate that about 4% of all feral cats in the U.S. are infected,” Dr. Julie Levy told Cornell’s Feline Health Center. “The condition is rare among kittens, because they don’t start with their high-risk behavior until they’re older. So, although older cats are more vulnerable, age in itself is not a determining factor. It’s a behavioral issue.”
How debilitating is the disease?
While the stages of an FIV infection “closely mirror those of HIV/AIDS,” Pedersen said, they tend to be asymptomatic or show “vague signs of illness for years.” That’s because the virus has had a significantly longer time to adapt to domestic cats than HIV has had to adapt to humans.
“Unlike HIV/AIDS, FIV-infected cats often live normal or near normal lives,” Pedersen explained. “Deaths during primary stage are rare. Most deaths occur after seven years or more from immunodeficiency-related illness or, most commonly, by the development of lymphoma.”
Once the disease progresses into old age, though, a cat’s health can significantly degrade until one or more illnesses overwhelm the compromised immune system.
According to the Feline Health Center, auxiliary health complications that accompany late-stage FIV include infections of the eyes, skin, and urinary and respiratory tracts, as well as dental issues. The cat will also become much more sensitive to cancers and blood disorders, while weight loss, seizures, vomiting, diarrhea, behavioral changes and neurological disorders could begin to set in.
Is there a cure?
“There is no cure at this time, other than providing a healthy and low-stress environment and treating whatever complication that arises the best that you can,” Pedersen told SAN.
The good news, however, is that when identified early enough, an FIV-positive cat can be nursed back to health and enjoy a long life before the disease becomes fatal.
“It is common for shelters to come across infected feral cats, most often intact males, that suffer from vague ill-health and common infections,” Pedersen said. “Such cats will often return to normal health when neutered, well-fed and treated, and converted to pets.”
