A 4-year-old boy presents to his pediatrician with intense perianal itching. His mother explains that the child has also been extremely irritable during the day and has not been sleeping well at night. Eggs with a flattened side were identified by the laboratory technician from a piece of scotch tape brought in by the parent. Infection with which of the following organisms is most likely?

  •  Ascaris lumbricoides
  •   Entamoeba histolytica
  •  Echinococcus granulosus
  •  Trichuris trichiura
  •  Enterobius vermicularis