10. A 28-yeаr-оld mаle pаtient returns frоm a trip tо a tropical region, where he stayed in rural areas with limited sanitation. A few days after returning, he develops fever, chills, and fatigue. He also complains of abdominal discomfort and diarrhea. Lab tests confirm the presence of an intestinal protozoan infection. Which of the following is the most likely mode of transmission for the patient’s infection?