This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'Which one of the following ricketsial diseases is transmitted by louse - \nSelect and explain. \nA. Epidemic typhus, B. Rockery mountain spotted fever, C. Q-fever, D. Endemic typhus', 'role': 'user'}, {'content': "Answer: A \nExplanation: Epidemic typhus has louse as vector. REF. PARK'S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICAL 21ST EDITION. PAGE NO - 274", 'role': 'assistant'}]