Help?

I've never really talked to anyone about this before but I need some advice. My husband and I have been together for almost two years. He has a daughter she's 3. I have two other kids and one with him. his daughter has came back from her moms with pin worms, lice, and scabbies (spelled?) we've documented everything from doctors and brought it to court and the judge didn't care at all. it's been a two year battle. I'm seriously worried for my childrens well being and being exposed to all this nasty stuff. Do I keep them separate until we know there's nothing wrong with her? I'm at a loss. thankfully they haven't got anything but lice but still it freaks me out. this child has also been molested as an infant, should we get her into some sort of counseling? idk what to do. ☹