1. 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

2. 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

3. 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

4. Rickettsia and Orientia
Organism Human Disease Distribution Spotted Fever Group R. Rickettsii Rocky Mountain spo.f. Western hem R. Africae African tick bite f Eastern-Sou Africa R. Akari Rickettsialpox Worldwid R. Australis Australian tick typhus Australia
R. Conorii Mediterranean spo. f Mediterranean R.japonica Japanese spotted f. Japan R. Sibirica Siberian tick typhus Siberia, Mongolia, Typhus group R. Prowazekii Epidemic Worldwide R.typhi Endemic Worldwide Scrub typhus group O.tsutsugamishi Scrub typhus Asia, Ocenia

5. Rickettsia and Orientia

6. Bite of brown dog tick-Rhipicephalus sanguineus

9. Rickettsia and Orientia
peptidoglycan layer is minimal
LPS has only weak endotoxin activity
binary fission is slow

10. 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

11. 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

13. Rickettsia and Orientia
Tissue culture and embrynonated eggs
Microscopy
Serology
PCR

14. Rickettsia and Orientia
Tetracycline
Fluroquinolones

15. Rickettsia and Orientia
Epidemic typhus
Louse-borne typhus
Humans are the primary reservoir
Replicates in endothelial cells with resulting vasculitis

16. Rickettsia and Orientia
Humans are the primary reservoir, with person-to-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

17. 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

18. Rickettsia and Orientia
MIF test is the diagnostic method of choice
Tetracyclines and chloramphenicol
Formaldehyde-inactivated typhus vaccine

19. Rickettsia typhi 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

20. Orientia tsutsugamushi
Scrub typhus
Mites
Asia, Oceania
6-18 days
Sudden onset
Maculo-papular rash
LAP, SM
Tetracycline, chloramphenicol

21. 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

22. Ehrlichia, Anaplasma, and Coxiella
Multiple morulae of Ehrlichia canis in DH82 tissue culture cells

23. 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

24. 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

25. 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

26. 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

27. Ehrlichia, Anaplasma, and Coxiella
Giemsa-stained preparations of peripheral blood should be performed, morulae diagnostic
PCR
Tetracycline, rifampin pregnant women
Vaccines are not available

28. Coxiella burnetii small, pleomorphic coccobacillus (0.2 to 0.7 μm)
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

29. 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

30. 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

31. 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

32. 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 trimethoprim-sulfamethoxazole