Yes, your landlord should have informed you of the infested apartment prior to renting it to you. You have clear evidence that the problem was pre-existing and that your manager did have knowledge of the infestation.

Since the landlord knowingly rented you an apartment that was infested, you can do several things:

1) Demand full treatment at their cost.
2) Demand reimbursement for any damage
3) Demand rent abatement for the time you were not able to use the unit
4) Move. (but NOT until the bedbugs are gone, or you will take them with you)

Since you are dealing with bedbugs, you will probably want to file a bedbug complaint with the RPA. There is a link at the top of the page to file a complaint. When filling out the complaint form state what you think the landlord should do to make this right. Remember, they were the ones that brought this hardship upon you.