Review Question - QID 108610

A 2-year-old male presents to the emergency department with diffuse pain. His parents say that he started experiencing fever, chills, and general distress this morning. His parents report that the patient was born abroad and that he has never had any previous serious illness. They deny any family history of disease but says that they are not sure if he has had genetics screenings or vaccinations. The patient has no sick contacts at home. His temperature is 103.1°F (39.5°C), blood pressure is 92/66 mmHg, pulse is 114/min, and respirations are 28/min. On physical exam, he appears to be in moderate distress with conjunctival pallor and inflammation of the 2nd digit of the left foot. A peripheral blood smear is performed and can be seen in Figure A. Which of the following is most likely responsible for the finding on peripheral blood smear?