Rickettsiaceae. Rickettsia, Orientia, Ehrlichia and Coxiella Aerobic,gram-negative bacilli (stain...
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Transcript of Rickettsiaceae. Rickettsia, Orientia, Ehrlichia and Coxiella Aerobic,gram-negative bacilli (stain...
Rickettsia, Orientia, Ehrlichia and Coxiella Aerobic,gram-negative bacilli (stain poorly) Obligate intracellular(cytoplasm of eucaryotic cells) Originally classified in a single family Distinct, unrelated genera according to their
analysis of DNA sequences Very small (originally thought to be viruses) Humans are accidental hosts (animals and
arthropods are reservoirs, and arthropods are vectors (ticks, mites, lice and fleas)
Rickettsia, Orientia, Ehrlichia and Coxiella Best seen by Giemsa and Gimenez All are strict intracellular parasites: Enter by phagocytosis Binary fission is slow (9-12 hours)
Rickettsia, Orientia, Ehrlichia and Coxiella Why obligate intracellular ? An energy
parasite: uses host cell ATP Outside the host cell unstable Coxiella resistant to desiccation
Rickettsiae
Spotted fever group(Benekli ateş): at least 17 rickettsiae
R. rickettsiiR.conorii,R. akari Typhus group:R.prowazekiiR.typhi*Bacteria replicate in endothelial cells , leakage from blood
vessels*Hypovolemia and hypoproteinemia
Rickettsiae
are maintained in reservoir hosts, primarily rodents and their arthropod vectors (e.g., ticks, mites, fleas)
Rickettsiae
The distribution of rickettsial diseases is determined by the distribution of the arthropod host/vector.
Most infections with tick vectors (e.g., spotted fevers) have a restricted geographic distribution, whereas rickettsial infections with other vectors such as lice (R. prowazekii), fleas (Rickettsia typhi), and mites (Rickettsia akari, Orientia tsutsugamushi) have worldwide distribution.
Rickettsiae
R. rickettsii: Rocky Mountain spotted fever(Kayalık dağlar benekli humması)
Vector: hard ticks (West hemisphere)Reservoir: ticks and wild rodentsTransmission: adult ticksMore than 90% infection occur from April to
October Transmission requires prolonged contact (24-48
hours)
Rickettsiae
R. rickettsii: Rocky Mountain spotted fever
Incubation 2-14 days after tick bite which may be painless and may not be remembered.
Fever, chills,headache, myalgias
Rash: macular to petechial, initially involves the extremities then spread to the trunk
Complications: gastrointestinal symtoms, respiratory failure, encephalitis and renal failure
Rickettsia rickettsii
Laboratory diagnosis:Microscopy and culture not useful.
Serology: Weil-Felix: agglutination test using Proteus antigens-
insensitive and nonspesific Rickettsia-spesific antibodies by Immunofluorescent
assay (IFA) Antibody response: 2-3 weeks Direct detection of antigen in biopsy specimens by IFA
or NAT(Nucleic acid amplification techniques).
Rickettsia rickettsii
Treatment Prevention and Control: Tetracycline(Doxycycline), chloramphenicol,
fluoroquinolone(ciprofloxacin) Delay in treatment:morbidity and mortality is
high(20%) No vaccine Avoidance of tick-infested areas, insect
repellents, prompt removeal of attached ticks Ticks survive as long as 4 years without feeding.
Other spotted fever Rickettsiae
R. akari: rickettsialpox USA, Soviet Union,Korea Rodents are resorvoirs, vectors:mouse
ectoparasites(mites) Usually mild Papulovesicular Doxycycline or chloramphenicol
Rickettsia prowazekii
Epidemic typus(Lekeli humma,klasik tifüs) Louse-borne typus Vector: Pediculus humanus (human body
louse) Reservoir:humans Epidemic typhus: in crowded unsanitary
conditions such as wars, natural diasters.
Rickettsia prowazekii
Epidemic typus 2-30 days incubation Nonspesific symptoms then high fever
headache, arthralgia, anorexia Some with petechial or macular rash Mortality may be as hig as 66% with
myocarditis and CNS dysfunction
Rickettsia prowazekii
Recrudescent disease (Brill-Zinsser disease):can occur in people years after their initial infection.
MIF is used for diagnosis Tetracycline and chloramphenicol Effective louse control measures Formaldehyde-inactivated vaccine in high risk
populations R. quintana:louse-born
Rickettsia typhi
Endemic typhus Worlwide distribution Reservoir: wild rodents Vector: flea Incubation:7-14 days the course usually
uncomplicated IFA Tetracycline, doxycycline or chloramphenicol Rodent reservoir control should be directed
Orientia tsutsugamushi
Scrub typhus(çalılık humması,Japon benekli humması)Asia, Japan
Vector: mites (chiggers, red mites) Reservoir:mites, wild rodents Incubation:6-18 days Maculopapular rash, headache,fever, myalgias Tetracycline, doxycycline or chloramphenicol
Ehrlichia
Ehrlichiosis Vector and reservoir: ticks Sennetsu fever:E. senetsu:raw fish with ehrlishia
infected flukes :restricted to Japan Three stages: elementary bodies, initial body and
morula Giemsa stain of peripheral blood: intracellular
organism Serology, probes Doxycycline
Coxiella burnetii
Q fever Worlwide No vector, by inhalation Reservoir: cattle,sheep,goats and cats Acute or chronic (mortality high) More closely related to Legionella and
Francisella
Coxiella burnetii
Stable to environmental conditions Survive in soil for years Excreted also by milk Atypical pneumonia