Ricketsia Flashcards
Rickettsia are obligate ______ pathogens and will not show up on Gram stain
intracellular
List the causative agent of Rocky Mountain Spotted Fever
Rickettsia rickettsii
List the causative agent of Mediterranean spotted fever
Rickettsia conorii
List the causative agent of African tick bite fever
Rickettsia africae
List the causative agent of murine (endemic) typhus and its mode of transmission
Rickettsia mooseri (typhi), fleaborne
List the causative agent of Q fever
Coxiella burnetti
List the causative agent of epidemic typhus and its mode of transmission
Rickettsia prowazekii, louseborne
List the two rickettsial diseases that can be transmitted by inhalation
Q fever (coxiella burnetii) epidemic typhus (Rickettsia prowazekii)
Describe the pathogenesis of Rickettsial diseases
- vasculitis caused by invasion of organism in the endothelium and smooth muscle of vessels
- thrombosis, occlusion, and necrosis of vessel walls
- thrombocytopenia (consumptive) and hemorrhage NOT true DIC
- capillary leakage resulting in edema, hypovolemia, hypotension, ARDS
- ADH produced in response to hypovolemia leading to hyponatremia
_____ is released in response to the hypovolemia seen in rickettsial infection, leading to hyponatremia
ADH
What is the classic triad seen in RMSF?
fever, headache, rash
- with appropriate travel/ exposure history
What geographic region is associated with RMSF?
Southeast US, especially North Carolina
The rash in RMSF is _____ - it starts in the extremities and moves toward the trunk
centripedal
Involvement of the ____ and ____ is considered a classic feature of the rash with RMSF
palms and soles
List other symptoms that are associated with RMSF
- myalgia
- abdominal pain
- nausea/ vomiting
- periorbital edema
- conjunctival suffusion
Will there be an eschar at the site of inoculation in RMSF?
NO eschar at the site of the tick bite
Outline the timeline of Rickettsia ricketsii infection
- 2-14 day incubation then fever, headache, myalgia
- petechial rash by day 3-5 of illness
How is the diagnosis of RMSF made?
Clinical suspicion (start antibiotics) Indirect immunofluorescent antibody (IFA) confirmation takes weeks
How is Rickettsia prowazekii transmitted?
Causative agent of epidemic typhus
Spread person to person by the human body louse
Outbreaks in times of war, natural disaster, great poverty- inability to bathe and wash clothes in hot water
Outline the timeline of Rickettsia prowazekii infeciton
Incubation of 8-16 days then severe headache, fever, myalgias, central rash
What are the main symptoms of epidemic typhus
sever headache, fever, myalgia, central rash, mental status changes
What animal is associated with outbreaks of epidemic typhus in the US?
Flying squirrels- asymptomatic reservoir
Found mainly in Southwest US
What is Brill-Zissner disease?
Mild, recrudescent form of epidemic typhus seen months-years after initial infection
How is Q fever transmitted?
Organism is aerosolozied from feces, urine, milk, infected placenta of sheep, cattle, goats
NO arthropod vector
What are the symptoms of Q fever?
range from self limited febrile illness to Q fever pneumonia (with severe headache), Q fever hepatitis, Q fever endocarditis
____________ is a characteristic histologic finding of Q fever
Donut shaped non-caseating granuloma
How is the diagnosis of Q fever made?
Specific serology
Mediterranean spotted fever is found in France, Spain, Africa, Asia, and is transmitted by ________
dog ticks
How does Mediterranean spotted fever present?
Fever, constitutional symptoms, generalized flat red rash, inoculation eschar at the site of the tick bite
Severe cases have neurologic involvement and peripheral gangrene
________ is the most common rickettsial infection seen in travel medicine
African tick bite fever
African tick bite fever is most strongly associated with what country?
South Africa
How is Rickettsia africae transmitted?
bite of cow tick
How does African tick bite fever present?
headache, myalgia, inoculation eschars (can have multiple), regional lymphadenopathy
can see mouth blisters and disseminated vesicular rash
List serologic tests that are used to diagnose rickettsial infections
- indirect immunofluorescent antibody
- indirect hemagglutination antibody
- complement fixation
either four fold increase or a single high titer is confirmatory
PCR is emerging
The _______ reaction was formerly used to diagnose rickettsia, but it is both insensitive and non-specific
Weil-Felix reaction
Why is early treatment so important in severe RMSF, Q fever, and typhus infections?
Prevention of severe endothelial damage helps avoid complications of multi-system organ failure
List drugs used to treat rickettsia infections
Doxycycline is DOC, can be given IV
Tetracycline
Chloramphenicol (not available in US, risk of aplastic anemia)
List some strategies to prevent rickettsia infection
Minimize exposure to arthropod vectors
Inspection for ticks, removal
Louse infestations must be treated
