We do feline rescues, and have for about 8 years. One of our newest "toss-aways" was in exceptional health up till about ten days ago. Suddenly, she became lethargic, lost weight and her skin appeared less "snappy" when you tugged on it. The worrysome thing was, her belly bloated up to twice it's size ( she actually looks pregnant!) but she is fixed. We started a Albon treatment ( thinking it was worms) and Amoxicyclin antibiotics. She still looks bloated and we feared FIV. Vets here charge several hundred dollars to test he, and economic times forbid our doing that right now.
None of the other 40-something cats are showing any signs of bloating or lethargy.