A fecal sample should show lungworm so I'm surprised the condition wasn't seen before since a fecal is usually part of the initial examination. Perhaps that wasn't done on Jimmy before this? I fostered a group of young cats a few years ago that had to be treated for lungworm. As soon as my vet heard the noisy breathing, and it was terrifyingly noisy in one young cat (called Skinny Girl by her original owner), my vet scooped out a small sample of poop and handed it over for testing. Some time later we heard shouts coming from the lab area of the clinic as the techs yelled at each other to come and see the slide. Apparently they'd never seen so many of the little beggers on one slide before. We knew that the cats had been starved, never having been given any cat food at all, so it wasn't surprising that they'd eaten whatever they could find. It always makes me heave to think of any animal eating slugs, yech!

We treated all the cats with Panacur, which I mixed in with their food, making sure they only ate their own small portions each time. They all fully recovered except for Skinny Girl, renamed Jazz, whose infestation had been so extreme. However, her adoptive family reports she only has slightly noisy breathing now when she's very active. I remember it was so noisy when I drove her home from the shelter that I almost pulled over on the freeway, thinking that she was dying. If she hadn't been rescued when she was, she most definitely would have died.

With that experience, I made the mistake of thinking a more recent foster had lungworm when she actually has asthma - I hadn't even thought of that possibility.

Good luck with making Jimmy well again. It is very hard when they have several different medical problems.