As everyone mentioned, fleas prefer a warm-blooded host. Most mites, and many other external parasites are host-specific. Ticks are the exception to this as they aren't very picky with whose blood they suck :flick:
Get that cat cleaned up and the house as well though. Not only are fleas a nuissance to the animals (and spread disease), but they have no problems going after people either! Spent a week at a friends place only to find out all his cats had become infested with fleas....and in turn those fleas went after me and the other humans in the apartment. Flea bites are NOT good times!