This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'Transovarian transmission is a feature of- \nSelect and explain. \nA. Scrub fever, B. Epidemic typhus, C. Endemic typhus, D. Trench fever', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The causative agent of scrub typhus: Rickettsia tsutsugamushi. It is the larva that feeds on veebrate hosts and picks up the rickettsias. The larval stage serves as both as a reservoir, through ovarian transmission and as a vector for infecting humans and rodents (refer pgno 300 park 23rd edition)', 'role': 'assistant'}]