Need advice with bed bug tenants please

[Justin Priestly]

We own a duplex in OH and have recently discovered that one side currently has had bugs for over a year. The other side (which was BB free) found a BB and we called an exterminator to have them inspect both sides to see what needs to be done. I had a talk with the "dirty" tenants and asked them to be honest and this is when they came clean that they have had them for some time. 

They have lied and hid this from us during multiple inspections. Clothes and things in garbage bags that they said was for goodwill, relocating sleeping quarters to different rooms for security reason, etc. we had our suspicions, thought maybe lice. They are no longer in their lease and have been month to month for around 3 years now. 

would you evict them and then exterminate? exterminate then evict them? or exterminate have them sign another lease with a BB clause and evict them if it happens again? 

How would you go about handling this situation?

Thanks