Ricketsia

Question 1

Rickettsia are obligate ______ pathogens and will not show up on Gram stain

Answer 1

intracellular

Question 2

List the causative agent of Rocky Mountain Spotted Fever

Answer 2

Rickettsia rickettsii

Question 3

List the causative agent of Mediterranean spotted fever

Answer 3

Rickettsia conorii

Question 4

List the causative agent of African tick bite fever

Answer 4

Rickettsia africae

Question 5

List the causative agent of murine (endemic) typhus and its mode of transmission

Answer 5

Rickettsia mooseri (typhi), fleaborne

Question 6

List the causative agent of Q fever

Answer 6

Coxiella burnetti

Question 7

List the causative agent of epidemic typhus and its mode of transmission

Answer 7

Rickettsia prowazekii, louseborne

Question 8

List the two rickettsial diseases that can be transmitted by inhalation

Answer 8

Q fever (coxiella burnetii)
epidemic typhus (Rickettsia prowazekii)

Question 9

Describe the pathogenesis of Rickettsial diseases

Answer 9

• 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

Question 10

_____ is released in response to the hypovolemia seen in rickettsial infection, leading to hyponatremia

Answer 10

ADH

Question 11

What is the classic triad seen in RMSF?

Answer 11

fever, headache, rash

- with appropriate travel/ exposure history

Question 12

What geographic region is associated with RMSF?

Answer 12

Southeast US, especially North Carolina

Question 13

The rash in RMSF is _____ - it starts in the extremities and moves toward the trunk

Answer 13

centripedal

Question 14

Involvement of the ____ and ____ is considered a classic feature of the rash with RMSF

Answer 14

palms and soles

Question 15

List other symptoms that are associated with RMSF

Answer 15

• myalgia
• abdominal pain
• nausea/ vomiting
• periorbital edema
• conjunctival suffusion

Question 16

Will there be an eschar at the site of inoculation in RMSF?

Answer 16

NO eschar at the site of the tick bite

Question 17

Outline the timeline of Rickettsia ricketsii infection

Answer 17

• 2-14 day incubation then fever, headache, myalgia

- petechial rash by day 3-5 of illness

Question 18

How is the diagnosis of RMSF made?

Answer 18

Clinical suspicion (start antibiotics)
Indirect immunofluorescent antibody (IFA) confirmation takes weeks

Question 19

How is Rickettsia prowazekii transmitted?

Answer 19

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

Question 20

Outline the timeline of Rickettsia prowazekii infeciton

Answer 20

Incubation of 8-16 days then severe headache, fever, myalgias, central rash

Question 21

What are the main symptoms of epidemic typhus

Answer 21

sever headache, fever, myalgia, central rash, mental status changes

Question 22

What animal is associated with outbreaks of epidemic typhus in the US?

Answer 22

Flying squirrels- asymptomatic reservoir

Found mainly in Southwest US

Question 23

What is Brill-Zissner disease?

Answer 23

Mild, recrudescent form of epidemic typhus seen months-years after initial infection

Question 24

How is Q fever transmitted?

Answer 24

Organism is aerosolozied from feces, urine, milk, infected placenta of sheep, cattle, goats
NO arthropod vector

Question 25

What are the symptoms of Q fever?

Answer 25

range from self limited febrile illness to Q fever pneumonia (with severe headache), Q fever hepatitis, Q fever endocarditis

Question 26

____________ is a characteristic histologic finding of Q fever

Answer 26

Donut shaped non-caseating granuloma

Question 27

How is the diagnosis of Q fever made?

Answer 27

Specific serology

Question 28

Mediterranean spotted fever is found in France, Spain, Africa, Asia, and is transmitted by ________

Answer 28

dog ticks

Question 29

How does Mediterranean spotted fever present?

Answer 29

Fever, constitutional symptoms, generalized flat red rash, inoculation eschar at the site of the tick bite
Severe cases have neurologic involvement and peripheral gangrene

Question 30

________ is the most common rickettsial infection seen in travel medicine

Answer 30

African tick bite fever

Question 31

African tick bite fever is most strongly associated with what country?

Answer 31

South Africa

Question 32

How is Rickettsia africae transmitted?

Answer 32

bite of cow tick

Question 33

How does African tick bite fever present?

Answer 33

headache, myalgia, inoculation eschars (can have multiple), regional lymphadenopathy
can see mouth blisters and disseminated vesicular rash

Question 34

List serologic tests that are used to diagnose rickettsial infections

Answer 34

• indirect immunofluorescent antibody
• indirect hemagglutination antibody
• complement fixation

either four fold increase or a single high titer is confirmatory

PCR is emerging

Question 35

The _______ reaction was formerly used to diagnose rickettsia, but it is both insensitive and non-specific

Answer 35

Weil-Felix reaction

Question 36

Why is early treatment so important in severe RMSF, Q fever, and typhus infections?

Answer 36

Prevention of severe endothelial damage helps avoid complications of multi-system organ failure

Question 37

List drugs used to treat rickettsia infections

Answer 37

Doxycycline is DOC, can be given IV
Tetracycline
Chloramphenicol (not available in US, risk of aplastic anemia)

Question 38

List some strategies to prevent rickettsia infection

Answer 38

Minimize exposure to arthropod vectors
Inspection for ticks, removal
Louse infestations must be treated