If mold is present and harmful to my health what is my landlords responsibility?

I rent a town home in omaha, NE and the ownership of the property changed in may. I have had a difficult time getting the landlord to make necessary repairs and so to be sure I purchased a mold kit from work took two samples one from under kitchen sink and laundry room sent it in with the $30.00 lab fee and recieved the results today stating there are 4 types of mold all capable of causing lung diseases and irritation to anyone with pre exisiting respitory conditions which my 5 yr old son has had asthma since he was 2 mo old. what are my rights and what is his responsibility as well as the time frame he must take care of said problem?