I have LOTS of experience with these lice. My daughter got them and did not mention it to me until it was horrific case. We tried tea tree oil. A whole bottle overnight, she had long hair wrapped in a towel. I wouldn't do that again.
Ao over the course of six months . I nit picked out in the sun. If there is one egg left on the hair shaft and it hatches. Then you are back to square one. I also washed her stuff constantly in hot water and bagged it while using stuff that had been in bags. I also had 3 feet of hair and never got it. My other family members never got it either.
For my grand daughter, I used a lighted magnifying glass my friend got lice and I picked her twice in a week between her using tea tree shampoo and she was over them. The combs don't get them all off the shaft you have to pick.