This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Social & Preventive Medicine
[{'content': 'Sandfly acts as a vector to all of the following diseases, EXCEPT \nSelect and explain. \nA. Oriental sore, B. Oraya fever, C. Kala-azar, D. Onchocerciasis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: (D) Onchocerciasis', 'role': 'assistant'}]