Who’s responsible for Bed Bugs?

I rented an unfurnished apartment in Philadelphia earlier this year for about 4 months, and rented furniture separately.  When I terminated my rental contracts with the apartment complex and the furniture rental company, the furniture rental company found bed bugs in the couch and bed I had rented.  I did notice bug bites on me while I lived there, but never thought about bed bugs.  Now the rental company refuses to pick up the furniture (which I didn’t inspect for bed bugs when it was delivered), and the apartment manager is going to send me a bill for the exterminator, lost rent, any other costs and lawyer feesto send me a letter.  The furniture company will also charge me for the bedding they are throwing out, lost rent, etc.

Am I responsible for all these charges?  I have no proof that the bed bugs were already there when I moved in, but they don’t have proof that they weren’t either.

I would appreciate some legal insight into this matter.

Thank you very much.