Rickettsial Diseases
General introduction
 Gram-negative, obligate intracellular
coccobacilli bacteria that infect
mammaols and arthropods
 Rickettsiae are transmitted in the
arthropods,which serves as both vector
and reservior
 Both DNA and RNA
 Is sensitive to antibiotic.
Category of rickettsia
 Genus
Rickettsia, Coxiella ,Orientia,Ehrlichia Bartonella
 Species
Rickettsia prowazekii (epidemic typhus),
Rickettsia typhi (endemic typhus), Rickettsia
rickettsii (spotted fever), Rochalimaea quintana
(trench fever), Coxiella burnetii (Q fever)
Bilogical features
 Variable shape,
coccobacilli
 Gram negative
 Microcapsule and slim
layer
 Culture : in york sacs of
embryonated eggs
Replication cycle of Rickettsia and
Orientia
Antigenic structure
 LPS
Rickettsia tsutsugamushi
Coxiella burnetii (Q fever)
LPSⅠ smooth
LPSⅡ rough
Weil-Felix reacrion
 Surface protein(SPA)
Transmission
 Typhus, spotted fever and trench fever are
transmitted via arthropod vectors;
 Q fever is acquired via inhalation or
ingestion of contaminated milk or food.
Pathogenesis
 Virulence factors: endotoxin,
phospholipase A, and slime layer
 Sites: vascular system producing
vasculitis血管炎
 Characteristic triad of symptoms: fever,
headache and rash (no rash with Q fever).
Rickettsia prowazekii
普氏立克次体
 epidemic typhus
 average incubation periods (days):8
 the louse
 Respiratory tract and conjunctiva
 Latent period: 2 weeks
 Abrupt onset,fever,chills,headache,
myalgia,arthralgia
Rickettsia typhi
地方性斑疹伤寒立克次体
 endemic typhus
 7-14 days
 Mice
 the louse&flea
 Mouth,nose and conjunctiva
 Gradual onset,fever,headache,myalgia,
cough
Rickettsia tsutsugamushi
恙虫病立克次体
 Tsutsugamushi disease(scrub typhus)
 Mice
 tsutsugamushi
 Black eachar焦痂
Coxiella burnetti贝纳柯斯体




Q fever
Cow and sheep
tick
High resistance
abrupt
onset ,fever,headache,chills,
myalgia,granulomatous
hepatitis
chronic diaease with
subacute
onset ,endocarditis,hepatic
dysfunction
Replication of C. burnetii
Generalized Life Cycle of Dermacentor variabilis and
Dermacentor andersoni Ticks
Bartonella henselae汉赛巴通
体
 CSD (cat scratch disease)
 Cat and dog
 Conjunctiva inflammation and lymph node
swell
Ehrlichia埃里希体属
 Ehrlichia chaffeensis: human
monocytotropic ehrlichiosis
 Ehrlichia sennetsu : human
granulocytotropic ehrlichiosis
Replication of Ehrlichia埃里希
体
Proposed life cycle for the agent of Human
Granulocytic Ehrlichiosis埃里希体病
Diagnosis
 The use of immunofluorescent antibodies to
examine a biopsy can be diagnostic.
 The organism can be inoculated into tissue
culture and grown over 4-7 days but this is very
hazardous to personnel.
 The Weil-Felix test looks for the production of
serum antibody that is reactive against Proteus
OX19, OX2 or OXK antigens but it is not always
reliable.
Control
 Sanitary: Arthropod and rodent control
 Immunological: No vaccines are currently
available.
 Chemotherapeutic: Tetracycline or
chloramphenicol are drugs of choice.