I would treat them all if they have been exposed to the dog which is known to have fleas. Frontline is a good choice. I would NOT use Revolution in a immune compromised cat. I assume by black nits you mean the black flecks you see in/on the coat, also sometimes called "flea dirt". It's actually dried BLOOD from the flea bites. If it's enough for you to SEE it without digging through the coat, the dog is indeed INFESTED BADLY and being EATEN ALIVE by this point.
Phaewryn (was Jenn, changed name) http://ucat.us http://ucat.us/domesticcatlinks.html Adopt a cat from Little Cheetah (UCAT) Cat Rescue: http://ucat.us/adopt.html PLEASE DONATE TO THE TANGLE FUND: Tangle is a cat in Greece that was severely injured when someone wrapped wire around his neck to strangle him, Little Cheetah Cat Rescue is raising funds to bring Tangle to Vermont to find him a good home! http://ucat.us/tangle-fund.html DONATE: We could really use a power saw (for construction), a digital camera (for pictures), and more towels! -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.394 / Virus Database: 268.8.1/354 - Release Date: 6/1/2006
