This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Tunica reaction is positive in ? 
Select and explain. 
A. R prowazekii, B. R typhi, C. R tsutsugamushi, D. R akari
B: R typhi
Answer: B: R typhi 
Explanation: Ans. is 'b' i.e., R typhi Neill - Mooser (Tunica) reaction When male guinea pigs are inoculated intraperitoneally with blood from a case of endemic typhus or with a culture of R. typhi (R. mooseri) they develop fever and a characteristic scrotal inflammation. This reaction is used to differentiate R. typhi and R. prowazekii.