What can I do legally.

My former wife and I have two children. And boy and girl, that we share 50/50 custody of . My former wife lives in a nasty run down apartment complex, my children have continually come back to my house with bed bug bites covering their body's and head lice. I have treated this matter for 3 1/2 months. I have bought the treatment to treat it at my house. I have also bought the treatment for her to treat at her house. But she will not use it. I have called CPS on this matter and have had medical documents to prove to them that they have had these issues. The case worker tells me. That he went to her house and found nothing. But in the same sentence told me he didn't look thoroughly. I took her to court in October for full custody and had my notes that I take on my children's well being when I get them back. But they shoved " parenting classes " in my face and didn't help me with any issues I had. I have multiple pictures of the bites on every occasion that they come back to me. But still no help from anyone. I am just wondering what I can do about this. And advise would be very helpful.