A 9-year-old girl presented to urgent care with acute painful irritation in her genital and anal area. She had been asleep for approximately two hours before awakening due to this sudden discomfort. Her parents reported that she had been scratching her vaginal area and walking with an altered gait over the previous three days. The patient reported that her vagina and anus had been painful and itchy at night during this time. Her medical history was only remarkable for intermittent constipation, and she did not have recent nausea, vomiting, or diarrhea. She had passed a formed bowel movement earlier that day. The patient was fully immunized and had no recent travel history.

Physical examination of the vagina revealed a live 1-cm, white worm wiggling in the introitus. Similar worms were observed in the anal area and moving along the intergluteal cleft (Figure 1). No blood or other abnormality was observed in the genital or anal area.

Question

Based on the patient's history and physical examination, which one of the following infections is the most likely diagnosis?

• A. Dientamoeba fragilis.

• B. Enterobius vermicularis (pinworm).

• C. Necator americanus (hookworm).

• D. Strongyloides stercoralis (threadworm).

• E. Trichuris trichiura (whipworm).