After almost three months in treatment, little Parsnip is back to her old self.

The tabby cat with expressive sky blue eyes had been diagnosed with Feline infectious peritonitis, a variation of feline coronavirus that attacks the body’s white blood cells and can render even the most playful kittens lethargic, eventually robbing them of their ability to walk and ultimately, their lives.

Parsnip was an affectionate whirlwind of energy when 21-year-old Californian Anae Evangelista adopted her. When she lost her kitten exuberance six weeks later, Evangelista knew something was wrong. When the little cat stopped eating and drinking, Evangelista realized the problem was much more serious than an initial veterinary examination suggested.

After more tests, she received grim confirmation that Parsnip had FIPV, a virus that is almost always fatal.

But a veterinarian connected her with an online group for people whose cats have FIPV and Evangelista was able to get her kitty accepted for experimental treatment with GS-441524, a nucleoside analogue antiviral drug that has proven effective at treating all types of FIP in several trials in recent years.

After a regimen of almost three months of GS-441524 treatment, Parsnip has her energy back, she’s gained a pound and a half, and “looks perfectly healthy,” Evangelista said. Equally important, her blood work and other health indicators are all positive.

She’s overjoyed at the result. Parsnip came into her life at a difficult time, when Evangelista was grieving the loss of two friends. Losing the kitten she’d bonded with — an animal who had become such a comfort to her over the months — would have been too much.

Evangelista will graduate from college in about a week’s time, “so I’m honestly so excited to have her ‘graduate’ from her treatment too,” she told PITB.

Londoner Billie’s cat, Jupiter, also suffers from FIPV. When she went to adopt him, Billie knew the British shorthair had Feline herpes virus (FHV) and that it would require careful monitoring. But the infection wasn’t life-threatening and Billie had already fallen in love with the golden-eyed chonkster.

When Jupiter’s appetite waned and his behavior changed earlier this year, Billie thought the little guy was just suffering from a FHV flare-up.

“He is very loving, he is like my shadow and he loves to play,” Billie told PITB, “but he wasn’t doing any of these things.”

As was the case with Parsnip, the veterinarians didn’t think Jupiter was seriously ill. They sent Billie and Jupiter home with antibiotics and anti-inflammatory medication, but after a week Jupiter still hadn’t improved. He was subject to a battery of tests — bloodwork, ultrasounds, x-rays — and kept overnight for observation.

“FIP is notoriously hard to diagnose, and there are so many symptoms that you could mistake for other things,” Billie said, noting veterinarians often have to “work backwards” and eliminate other potential ailments before diagnosing a cat with FIPV. “Jupiter’s symptoms were so minor initially, he just seemed a bit off and hadn’t eaten much and felt hot. I think because I know him and his behavior so well, we were able to catch it early.”

Because the tests didn’t confirm FIPV, a third visit with more tests followed before Jupiter was placed on his meds. While the FDA has yet to approve GS-441524 treatment in the US, the UK had approved the drug in fall 2021, so Jupiter was able to begin treatment right away. Like Evangelista, who paid $5,000 for the FIPV drugs, not including the initial veterinary examinations, Billie was faced with hefty bills: The three initial veterinary visits, tests and five nights of observation added up to £5,500 (about $6,930 in USD), and the medication set her back £7,500 (about $9,400).

Her family helped her pay the initial veterinary bills, her sister started a GoFundMe campaign, and her nieces began making “FIP Warrior crystal healing bracelets,” with the proceeds from sales going to Jupiter’s treatment. (A GoFundMe for Parsnip also exists, and has raised $2,060 of its $2,500 goal so far.)

So far, Jupiter is responding well to the treatment and the signs are encouraging.

Both cats will enter an 84-day observation period after their regimens. They’ll have their bloodwork monitored and will be examined several times over that stretch to make sure they’ve recovered. They’ll also be closely watched at home for any symptoms.

Evangelista and Billie said they’re heartened by the 85 percent success rate.

Despite the cost, Billie said she didn’t balk at taking care of her cat.

“Jupiter is my whole world,” Billie said. “It is just the two of us, he is my one constant and he means everything to me. He is so loving, and so sassy. He has such a little personality and I would be so lost without him.”

Follow Jupiter on Instagram @_jupitersfipfight and Parsnip at @lilmissparsnip