1. Rickettsia

4. Rickettsia is a diverse collection of obligate intracellular parasites found in ticks, lice, fleas, mites and mammals Smaller than bacteria and the other biological characteristics are similar to bacteria (e.g., binary fission, cell wall, sensitive to antibiotics, containing DNA and RNA).

5. There are 5 genera in Rickettsia –Rickettsia –Ehrlichia –Orientia –Coxiella –Bartonella

6. Many species of Rickettsia cause zoonosis in human (rickettsial diseases) mediated by the arthropods ( 节肢动物 ). R. prowazekii: human louse (vector), epidemic typhus. R. mooseri: mouse flea (vector), endemic typhus ( 斑疹伤寒 ). O. tsugamushi: Chigger (vector), scrub typhus ( 恙虫病 ). C. burnetii: tick (vector), Q fever.

7. Virulent factors phospholipase A LPS capsule

8. Laboratory diagnosis: Isolation and culture, PCR, serological examinations and Weil-Felix test. Weil-Felix test: Because somatic antigens of Bacillus proteus strains (OX-K and OX19) have common antigens with Orientia tsugamushi (OX-K), Rickettsia prowazekii (OX19) and Rickettsia mooseri (OX19), they are used to detect serum antibodies of patients with rickettsial diseases.

9. Treatment: Tetracycline is the first choice for therapy. Prevention: No vaccine is available.