A couple of months ago we had an absolute nightmare with fleas. We've always treated our cats regularly, but briefly switched to flea collars - which didn't work, then resuming the previous treatment failed to get rid of them (and yes, we treated the house too).
We got the industrial strength stuff from the vets, continued nuking the house, and haven't seen a flea since October. UNTIL TODAY. I've just found one on my hand after a little snuggle with the cat.
Now, veteran flea-sufferers will know, the eggs can survive in your house a while, even if you hoover thoroughly - and the pupae can last aaaaaaaages. So it could just be a random one (hatched in the house or picked up outside) that was already destined for death as soon as it bit either cat, and would never have been able to breed. Or....not. I am getting the heebie-jeebies about the possibility of not. The treatment is due every 13 weeks, and next dose should be January 6th.
What do I do? Trust the vet-strength prescription stuff? Treat early? Cry?