Rickettsia

• 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).

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

• 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.

Virulent factors

• phospholipase A

• LPS

• capsule

• 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.

• Treatment: Tetracycline is the first choice for therapy.

• Prevention: No vaccine is available.