Broadline is the one for cats. Ive got one in the cupboard, just checked, kills fleas in 24hrs, and kills the larvae stage for a month. You get 6 in a box. The one thing you do need to keep reapplying. It says monthly. Ive noticed scratchy needs redoing frequently for ticks. He gets loads round his neck. Anymore than 6 weeks and i usually find a new tick on him.
If youve got fleas in the house you'll see them jumping. Its not too difficult to get rid of them. You can buy canisters that you set off in the house, shut everything up, i think you open cupboards to allow it to permeate draws etc, then go for a walk for a few hours. You need several i think to cover all the house. They cover so many square metres.
Only seen them once in a house, while someone was away on holiday, the fleas came to play. I was itching for days.