Rickettsiaceae

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.

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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

Coxiella burnetii

Can be cultered(not commonly used) Serology Amplification techniques