rickettsia

RICKETTSIARICKETTSIA

ELIZABETH P. QUILES, M.D.,FPASMPELIZABETH P. QUILES, M.D.,FPASMP

DEPARTMENT OF MICROBIOLOGYDEPARTMENT OF MICROBIOLOGY

OUR LADY OF FATIMA UNIVERSITYOUR LADY OF FATIMA UNIVERSITY

COLLEGE OF MEDICINECOLLEGE OF MEDICINE

RICKETTSIARICKETTSIACHARACTERISTICS:CHARACTERISTICS:

• Structurally similar to gram (-) bacilliStructurally similar to gram (-) bacilli

- DNA & RNA- DNA & RNA

- enzymes for Kreb’s cycle- enzymes for Kreb’s cycle

- ribosomes for protein synthesis- ribosomes for protein synthesis

- inhibited by antibiotics - inhibited by antibiotics Tetracycline & ChloramphenicolTetracycline & Chloramphenicol

• Originally thought to be viruses Originally thought to be viruses because:because:

- small size- small size

- stain poorly with gram stain- stain poorly with gram stain

- grows only in cytoplasm of - grows only in cytoplasm of Eukaryotic cellsEukaryotic cells

- obligate intracellular parasites - obligate intracellular parasites EXCEPT CoxiellaEXCEPT Coxiella

• Reservoirs – animals & arthropodsReservoirs – animals & arthropods• Humans are accidental hostsHumans are accidental hosts• Cell wall:Cell wall:

- peptidoglycan- peptidoglycan - LPS – have weak endotoxic - LPS – have weak endotoxic activity (absent in Ehrlichia) activity (absent in Ehrlichia)

• Genera: Genera: RickettsiaRickettsia RochalimaeaRochalimaeaCoxiellaCoxiella EhrlichiaEhrlichiaOrientiaOrientia

• Stains weakly with gram stain Stains weakly with gram stain Giemsa Giemsa or Gimenez stainor Gimenez stain

• Easily destroyed by heat, drying & Easily destroyed by heat, drying & bactericidal agents EXCEPT Q bactericidal agents EXCEPT Q fever fever due to the formation of due to the formation of endospore-like structure by C. endospore-like structure by C. burnettiburnetti

• Intracellular location:Intracellular location:

typhus group – cytoplasmtyphus group – cytoplasm

spotted fever group – nucleusspotted fever group – nucleus

Rochalimaea – surface of Rochalimaea – surface of Eukaryotic cellsEukaryotic cells

Coxiella & Ehrlichia – Coxiella & Ehrlichia – cytoplasmic cytoplasmic vacuolesvacuoles

PATHOLOGYPATHOLOGYMultiply in endothelial cells of small blood vesselsMultiply in endothelial cells of small blood vessels

VasculitisVasculitis

(skin – rashes;other organs – DIC & vascular (skin – rashes;other organs – DIC & vascular occlusion)occlusion)

Swollen & necroticSwollen & necrotic

Thrombosis of the vesselsThrombosis of the vessels

VECTORS:VECTORS:

RMSF – Dermacentor andersoniRMSF – Dermacentor andersoni

Rickettsialpox – Allodermanyssus Rickettsialpox – Allodermanyssus sanguinussanguinus

Scrub typhus – trombiculid mitesScrub typhus – trombiculid mites

Epidemic typhus – Pediculus Epidemic typhus – Pediculus humanushumanus

Ehrlichiosis – Amblyomma Ehrlichiosis – Amblyomma americanus (lone star tick)americanus (lone star tick)

Trench fever – Pediculus humanusTrench fever – Pediculus humanus

Murine typhus – Xenopsylla cheopis &Murine typhus – Xenopsylla cheopis &

Ctenophalides felisCtenophalides felis

RICKETTSIAL INFECTIONSRICKETTSIAL INFECTIONS

• Fever, headache, malaise, prostration, skin Fever, headache, malaise, prostration, skin rash & hepatosplenomegalyrash & hepatosplenomegaly

• Classified into groups:Classified into groups:1. Typhus Group – Epidemic typhus, 1. Typhus Group – Epidemic typhus, Murine Murine typhus, Scrub typhustyphus, Scrub typhus2. Spotted Fever Group – RMSF, 2. Spotted Fever Group – RMSF, RickettsialpoxRickettsialpox3. Q Fever3. Q Fever4. Trench fever4. Trench fever5. Ehrlichiosis5. Ehrlichiosis

TYPHUS GROUPTYPHUS GROUP

• Maculopapular rashes with the Maculopapular rashes with the sparing of the palms & solessparing of the palms & soles

EPIDEMIC TYPHUS EPIDEMIC TYPHUS (LOUSEBORNE TYPHUS)(LOUSEBORNE TYPHUS)

• Etiology: R. prowazekiiEtiology: R. prowazekii

• severe systemic infection & severe systemic infection & prostration prostration

• more fatalmore fatal

• Brill-Zinsser Disease Brill-Zinsser Disease recrudescent diseaserecrudescent disease

ENDEMIC TYPHUS ENDEMIC TYPHUS (MURINE TYPHUS)(MURINE TYPHUS)

• Etiology: R. typhiEtiology: R. typhi

• similar features with Epidemic similar features with Epidemic typhus but milder & rarely fatal typhus but milder & rarely fatal except in the elderlyexcept in the elderly

SCRUB TYPHUSSCRUB TYPHUS

Etiology: Orientia tsutsugamushiEtiology: Orientia tsutsugamushi

• resembles Epidemic typhus except resembles Epidemic typhus except for the ESCHAR for the ESCHAR

• generalized lymphadenopathy & generalized lymphadenopathy & lymphocytosislymphocytosis

• cardiac & cerebral involvement may cardiac & cerebral involvement may be severebe severe

SPOTTED FEVER GROUPSPOTTED FEVER GROUP

• Rash appear 1Rash appear 1stst on the extremities on the extremities with involvement of the palms & with involvement of the palms & solessoles

RICKETTSIALPOXRICKETTSIALPOX

• Etiology: R. akariEtiology: R. akari

• mild disease resembling Varicellamild disease resembling Varicella

• firm red macule at the bite site firm red macule at the bite site deep-seated vesicle deep-seated vesicle eschar eschar

Q FEVER (QUERY FEVER)Q FEVER (QUERY FEVER)

• Etiology: Coxiella burnettiEtiology: Coxiella burnetti

• MOT: inhalation of dust containing MOT: inhalation of dust containing the organism or aerosolsthe organism or aerosols

• Excreted in the urine, feces & milkExcreted in the urine, feces & milk

• Individuals at risk: food handlers, Individuals at risk: food handlers, ranchers & veterinariansranchers & veterinarians

• Resembles Influenza & nonbacterial Resembles Influenza & nonbacterial pneumonia, hepatitis or pneumonia, hepatitis or encephalopathyencephalopathy

• No rash or local lesionNo rash or local lesion

• Weil Felix test (-)Weil Felix test (-)

TRENCH FEVERTRENCH FEVER

• Etiology: R. quintanaEtiology: R. quintana

• Manifestations: headache, Manifestations: headache, exhaustion, pain, sweating, cold exhaustion, pain, sweating, cold extremities & fever with roseolar extremities & fever with roseolar rashrash

• Relapses occurRelapses occur

EHRLICHIOSISEHRLICHIOSIS

• ETIOLOGY:ETIOLOGY:E. sennetsu – Sennetsu feverE. sennetsu – Sennetsu feverE. chaffeensis – Human E. chaffeensis – Human

ehrlichiosusehrlichiosus• Leukocytic rickettsia – parasitize Leukocytic rickettsia – parasitize

lymphocytes, neutrophils & lymphocytes, neutrophils & monocytesmonocytes

SENNETSU FEVER:SENNETSU FEVER:

• Fever, cervical lymphadenopathy, Fever, cervical lymphadenopathy, inc. peripheral mononuclear cells & inc. peripheral mononuclear cells & atypical lymphocytesatypical lymphocytes

HUMAN EHRLICHIOSIS:HUMAN EHRLICHIOSIS:

• Similar to RMSFSimilar to RMSF

• Leukopenia & thrombocytopeniaLeukopenia & thrombocytopenia

• Only 20% of cases present with rashOnly 20% of cases present with rash

DIAGNOSISDIAGNOSIS

• Weil-Felix test – not specificWeil-Felix test – not specific

• Serological tests – most sensitive & Serological tests – most sensitive & specificspecific

- microimmunofluorescence- microimmunofluorescence

- microagglutination- microagglutination

- complement fixation- complement fixation

DISEASEDISEASE WEIL-FELIXWEIL-FELIX

OX19OX19 OX2OX2 OXKOXK

Epidemic typhusEpidemic typhus ++++ +/-+/- --

Endemic typhusEndemic typhus ++++ -- --

Scrub typhusScrub typhus -- -- ++++

RMSFRMSF ++ ++ --

RickettsialpoxRickettsialpox -- -- --

Q feverQ fever -- -- --

Trench feverTrench fever ?? ?? ??