Regarding the roundworms -- I will assume your vet did a fecal exam and that is how the worms were found (as opposed to "It's a kitten, of course it has worms." ). The breeder probably should have known and/or said something. You might want to contact the breeder and let the person know. If I'm very generous, I would say the breeder didn't know.

Regarding the kitty cold -- The kitty cold is not from the breeder. My best guess is he picked it up from the vet visit or from Chloe. I have 'fragile' cats so it's not uncommon for one to get a kitty cold 3-6 days after visiting the vet's. Then they tend to pass it on to my other cats, some who may not show many symptoms. Finally, 2-3 weeks later, the last cat gets sick -- and it all stems from the one vet visit. Chloe could have been harboring the germs, Eugene could have gotten from the vets, heck you could have brought it in! A simple kitty cold isn't hard to get.

I hope by now Eugene is over most of the cold and is doing better!