I bought my house 17 months ago and have had rodent problems since day one, can I sue?

Unfortunately, you probably do not have a case. When you close on a house, you take it subject to the shape it was in. The assumption is that you looked over the property yourself and also had it inspected, or at least had the opportunity for an inspection. The only situation under which you *might* have a case is:

1) Seller knew about the pests (you have to be able to show this)--it's not enough that seller may have had pests, but seller had to be ware of them.

2) Seller specifically lied about the pests--not merely that they didn't disclose them, but in some may made actual misreprentations about them.

3) You could not or should have been able to have spotted evidence of the pests (e.g. there was no way a home inspector or a diligent buyer doing a walk through would spot the evidence), since if you could have seen evidence yourself, you probably could not have simply relied on seller's misrepresentations.

Also, after 17 months, it would be dificult to show evidence that the pests were there when you purchased, or that the pests haven't moved in since then. Given these challenges and the cost of suing, it may well be the case that a lawsuit would not be in your best interest.