flea dirt

Question
I just took in 2 9 month old cats that were neglected. They were treated for fleas months ago,not by me, but never bathed or brushed after.  I do not see any fleas and when I was at the vet he said it is too cold for fleas.  Prior to 3 days ago they were living in a garage and it has generally been around 25 degrees.  
Tonight while combing I noticed flea dirt, however they are not itching and no visible fleas.  Is it possible this flea dirt could still be present from before, one cat is a long hair and the other short, but extremely thick coarse fur.
Or am I in for trouble now that they are in my house, Do they still have fleas and should I treat them?  Oh they are also very sick with upper resp inf. and currently taking amoxocilan.
Thanks.

Answer
Hi Lori,

If you saw flea dirt then there are fleas. It may be too cold for fleas outside but that doesn't mean your cat doesn't have them. And fleas can hide any place in a garage waiting for that nice warm host to come on down. Get either Advantage or Frontline for the cats. Better yet, ask your vet for Capstar for both cats and then treat them with that first then the other flea stuff. Capstar will kill any fleas on them immediately. Frontline or Advantage will keep them from getting any back in case they brought some in the house with them. And don't worry about that. No host for them to live on, fleas die. Good luck and a good for you for taking care of them.

Ciao, Karen