Transcript Rickettsia and Orientia

Rickettsia and Orientia
• Rickettsia (Rickettsia and Orientia)
•Ehrlichia (Ehrlichia and Anaplasma)
•small (0.3 × 1 to 2 μm)
•stained poorly with the Gram stain
•grew only in the cytoplasm of
eukaryotic cells
Rickettsia and Orientia
• structurally similar to gram-negative
rods
• contain DNA, ribonucleic acid (RNA),
and enzymes and ribosomes
• multiply by binary fission
• inhibited by antibiotics
Rickettsia and Orientia
• maintained in animal and arthropod
reservoirs
• transmitted by arthropod vectors
(e.g., ticks, mites, lice, fleas)
• humans are accidental hosts
• spotted fever group and the typhus
group
Rickettsia and Orientia
• Organism
Human Disease
Spotted Fever Group
R. Rickettsii
Rocky Mountain spo.f.
R. Africae
African tick bite f.
R. Akari
Rickettsialpox
R. Australis
Australian tick typhus
R. Conorii
Mediterranean spo. f.
R.japonica
Japanese spotted f.
R. Sibirica
Siberian tick typhus
Typhus group
R. Prowazekii
Epidemic
R.typhi
Endemic
Scrub typhus group
O.tsutsugamishi
Scrub typhus
Distribution
Western hem
Eastern-Sou Africa
Worldwid
Australia
Mediterranean
Japan
Siberia, Mongolia,
Worldwide
Worldwide
Asia, Ocenia
Rickettsia and Orientia
Bite of brown dog tickRhipicephalus sanguineus
Rickettsia and Orientia
• peptidoglycan layer is
minimal
• LPS has only weak
endotoxin activity
• binary fission is slow
Rickettsia and Orientia
• No toxins
• No host immune response
• R. rickettsii is most common rickettsial
pathogen in United States
• Hard ticks are the primary reservoirs and
vectors (Dermacentor)
• Transmission requires prolonged contact
(24 to 48 hours)
• Distribution in Western hemisphere
• Disease is most common April through
October
Rickettsia and Orientia
• 2-14 days
• Painless tick bite
• High fever, headache, fever, chills
• Rash macular to petechial
• First extremities and then trunk
• GIS symptoms, respiratory failure
• Encephalitis, renal failure
Rickettsia and Orientia
• Tissue culture and embrynonated
eggs
• Microscopy
• Serology
• PCR
Rickettsia and Orientia
• Tetracycline
• Fluroquinolones
Rickettsia and Orientia
• Epidemic typhus
• Louse-borne typhus
• Humans are the primary reservoir
• Replicates in endothelial cells with
resulting vasculitis
Rickettsia and Orientia
• Humans are the primary reservoir, with personto-person transmission by louse vector
• It is believed that sporadic disease is spread from
squirrels to humans via squirrel fleas
• Recrudescent disease can develop years after
initial infection
• People at greatest risk are those living in
crowded, unsanitary conditions
• Disease is worldwide, with most infections in
Central and South America and Africa
• Sporadic disease is seen in the eastern United
States
Rickettsia and Orientia
• 2- to 30-day incubation period
• nonspecific symptoms
• less than 40% of the patients had a
petechial or macular rash
• myocarditis and central nervous
system dysfunction
• Brill-Zinsser disease-milder
Rickettsia and Orientia
• MIF test is the diagnostic method of
choice
• Tetracyclines and chloramphenicol
• Formaldehyde-inactivated typhus
vaccine
Rickettsia typhi
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Endemic or murine typhus
worldwide
Rodents are the primary reservoir,
Rat flea (Xenopsylla cheopis) is the
principal vector
7 to 14 days
A rash develops
Typically restricted to the chest and
abdomen
Indirect fluorescent assay
Orientia tsutsugamushi
• Scrub typhus
• Mites
• Asia, Oceania
• 6-18 days
• Sudden onset
• Maculo-papular rash
• LAP, SM
• Tetracycline, chloramphenicol
Ehrlichia, Anaplasma, and Coxiella
• Anaplasmataceae: Anaplasma, Ehrlichia,
Neorickettsia, and Wolbachia
• survival within a cytoplasmic vacuole
in the infected arthropod or
mammalian cell
• infection of hematopoietic cells
Ehrlichia, Anaplasma, and Coxiella
Multiple morulae of Ehrlichia canis in DH82 tissue culture cells
Ehrlichia, Anaplasma, and Coxiella
• Small, intracellular bacteria
• Stain poorly with Gram stainReplicates in
phagosome of infected cells
• Intracellular growth protects bacteria from
immune clearance
• Able to prevent fusion of phagosome with
lysosome of monocytes or granulocytes
• Initiates inflammatory response that
contributes to pathology
Ehrlichia, Anaplasma, and Coxiella
• Depending on the species of Ehrlichia, important
reservoirs are white-tailed deer, white-footed
mouse, etc
• Ticks are important vectors, but transovarian
transmission in inefficient
• Disease in United States is most common in the
Atlantic states; northern, central, and southern
Midwest states; and northern California
• People at greatest risk are those exposed to ticks
in the endemic areas
• Disease is most common from April to October
Ehrlichia, Anaplasma, and Coxiella
• Human monocytic ehrlichiosis is caused by E.
chaffeensis
• 1 to 3 weeks after a tick bite, patients develop a
flulike illness with fever, headache, and myalgias
• Gastrointestinal symptoms develop in fewer than
half the infected patients
• late-onset rash develops in 30% to 40% of
patients
• Leukopenia, thrombocytopenia, and elevated
serum transaminases
Ehrlichia, Anaplasma, and Coxiella
• Canine Granulocytic Ehrlichiosis E. ewingii
• Human anaplasmosis, A. phagocytophilum
• More than half the infected patients require
hospitalization, and severe complications are
common
• Mortality is rare
Ehrlichia, Anaplasma, and Coxiella
• Giemsa-stained preparations of peripheral blood
should be performed, morulae diagnostic
• PCR
• Tetracycline, rifampin pregnant women
• Vaccines are not available
Coxiella burnetii
• more closely related to Legionella and
Francisella
• Q fever, which may be asymptomatic in
humans and develops either acutely or as a
chronic infection
• small, pleomorphic coccobacillus (0.2 to
0.7 μm)
• The small replicating cells will mature to
large-cell variants, which then evolve to
stable spores
Coxiella burnetii
• inhalation of airborne particles
• more by the environment
• Coxiella proliferate in the respiratory
tract and then disseminate to other
organs
• pneumonia and granulomatous
hepatitis
• most chronic infections manifest as
endocarditis
Coxiella burnetii
• antigenic variation
• C. burnetii is extremely stable in harsh
environmental conditions
• Many reservoirs, including mammals, birds, and
ticks
• Most human infections associated with contact
with infected cattle, sheep, goats, dogs, and cats
• Most disease acquired through inhalation;
possible disease from consumption of
contaminated milk; ticks are not an important
vector for human disease
• Worldwide distribution
• No seasonal incidence
Coxiella burnetii
• Acute diseases include influenza-like
syndrome, atypical pneumonia,
hepatitis, pericarditis, myocarditis,
meningoencephalitis
• Chronic diseases include
endocarditis, hepatitis, pulmonary
disease, and infection of pregnant
women
Coxiella burnetii
• most common presentation of chronic Q fever
is subacute endocarditis
• culture (not commonly performed),
polymerase chain reaction (PCR), or by
specific serologic tests
• serology is the most commonly used
diagnostic test
• Tetracycline
• combination of drugs, such as rifampin
and either doxycycline or trimethoprimsulfamethoxazole