Get on to your local council. Not only do the have a legal obligation to control rats but they can also make him tidy his place up. It won't happen overnight but keep putting the complaints in, in writing, and they can ultimately turn up with a lorry and get to work then give him the bill. In the meantime you can't do a lot more than read ditchshitters thread and do exactly what it says on the can. Even though your neighbours aren't getting rats, no doubt because they don't keep chickens, can you get them on side to complain about the mess/eyesore?