A 14-year-old boy came to the clinic with her mother, complaining of intense itching on his scalp for the past few days. The mother reports that he has noticed his son scratching his head frequently, particularly at night. He has been irritable and has had difficulty concentrating in school. The mother also mentions that the child has recently returned from a summer camp. No other family members have similar symptoms. He has no significant past medical history, and he is up to date on his vaccinations. He has not had any recent illnesses or infections. His physical examination revealed tiny white nits attached to the hair shafts, particularly at the posterior hairline and behind the ears, as shown in the image. There were no signs of infection or inflammation beyond the localized irritation from scratching. Which of the following diagnoses is most likely,