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
Rickettsial agent of Epidemic typhus is 
Select and explain. 
A. R. prowazekii, B. R. typhi, C. R. tsutsugamushi, D. R. canorii
A: R. prowazekii
Answer: A: R. prowazekii 
Explanation: (R-prowazekii) (239-PK) (262- Park 20th)DiseaseRickettsial agentInsect vectorsMammalian reservoirsITyphus group a. Epidemic typhusR. prowazekiiLouseHumansb. Murine typhusR. typhiFleaRodentsc. Scrub typhusR. tsutsugamushiMiteRodentsIISpotted fever group a. Indian tick typhusR. conoriiTickRodents, dogsb. Rocky Mountain spotted feverR. rickettsiiTickRodents, dogsc. Rickettsial poxR. akariMiteMiceIIIOthers a. Q-feverC. burnetii-Cattle, sheep, goatsb. Trench feverRochalimaeaquintanaLouseHumans