L 80 Rickettsial Infections

Question 1

What type of pathogen is Rickettsia?

Answer 1

Obligate intracellular parasites

Question 2

Characteristics of rickettsiaceae

Answer 2

Gram (-) very small

Induce phagocytosis to enter host cells and grow in cytoplasm or nucleus

Question 3

Vectors of rickettsiaceae

Answer 3

Many different vectors:
Ticks, Mites, Louse
Remember that these are also hosts for the rickettsiaceae

Question 4

Where do rickettsiaceae like to multiply in the body?

Answer 4

Often multiply in the endothelial cells of small blood vessels of the skin and other organs => necrotizing vasculitis
Also causes INCREASED MICROVASCULAR PERMEABILITY
This causes damage and consequences in tissues highly dependent on blood flow

Question 5

Rickettsial vasculitis leads to what symptoms?

Answer 5

Rash, headache, encephalitis, nephritis, myocarditis, lesions in lungs and liver and GI

Question 6

What is the most common first set of Sx for rickettsia infection?

Answer 6

High fever and Severe headache

Question 7

What are the 4 species of rickettsia to know, their associated diseases, and worldwide distribution?

Answer 7

R. rickettsii: RMSF, western hemisphere
R. akari: rickettsialpox, worldwide
R. prowazekii: Epidemic typhus, worldwide
R. typhi: murine typhus, worldwide

Question 8

What are the reservoir hosts of R. rickettsii? What are the vectors?

Answer 8

Mammaliam reservoirs: wild rodents and other small mammals

Vectors: american dog tick, rocky mtn wood tick, brown dog tick (AZ)

Question 9

R. rickettsii incubation and SSx

Answer 9

Incubation 2-14d
Fever and severe headache
Rash 2-5d after fever often starts at wrists and ankles and works inward (Centripetal)

Question 10

R. rickettsii complications

Answer 10

Myocarditis, CNS dysfunction, renal failure, gangrene, pneumonia
All come from vascular damage
Early treatment essential

Question 11

R. akari epidemiology, reservoirs and vector

Answer 11

Mild disease
Found in urban areas like NYC
House mice and rats reservoir
House mouse mite vector

Question 12

R. akari disease

Answer 12

Rickettsialpox:
Mild disease
Incubation 7-10d
1st phase: red papule at bite site becomes vesicular and forms eschar
2nd phase: 3-7d later, sudden fever and severe headache, chills, rigors, sweating, myalgia
Rash 2-3d after fever onset

Generally self-limited even without treatment

Question 13

R. prowazekii epidemiology

Answer 13

Louse-bourne typhus, serious disease that causes lots of death
Worldwide: prison camps, refugees, crowding and poor hygiene
In US: usually exposure to fleas from flying squirrels, or among the homeless who get lice
Humans are reservoir
Human body louse vector

Question 14

Infection of R. prowazekii in humans

Answer 14

Human body louse bites and then defecates. Getting the feces into the wound or a scratch causes the disease.

Question 15

R. prowazekii disease

Answer 15

Very serious disease
Incubation 7-14 days
Sudden fever and severe headache, tachypnea, myalgia
Rash 4-7d after fever begins on trunk and goes to extremities (centrifugal)

Question 16

R. prowazekii complications

Answer 16

CNS dysfunction, myocarditis, pneumonia, renal failure, gangrene, multi organ system failure
Early treatment important

Question 17

R. prowazekii long term effects

Answer 17

If survive the disease, the bug may remain for decades and come back to cause Brill-Zinnser disease: symptoms less servere

Question 18

Sylvatic epidemic typhus

Answer 18

Symptoms less severe
Eastern USA
Southern flying squirrels reservoir
Squirrel flea vector

Question 19

R. typhi epidemiology

Answer 19

Causes endemic or murine typhus
Worldwide
Reservoir: rats, mice, cats, opossums
Vectors: fleas
Seen in coastal port areas, also Texas
Transmission through flea feces

Question 20

R. typhi disease

Answer 20

Incubation 7-14d

Similar to epidemic typhus (this is endemic) nut less severe and shorter

Question 21

Rickettsiosis diagnosis

Answer 21

Fever, headache, rash, etc.
Hx of arthropod bites
Serology, rash biopsy

Question 22

Rickettsiosis treatment

Answer 22

Doxycycline

Chloramphenical if doxy contraindicated

Question 23

Rickettsiosis prevention

Answer 23

Tick control and precautions

Control rodents, mass delousing

Question 24

Characteristics of Anaplasmataceae

Answer 24

Gram (-)
Like to target cells of hematopoietic origin–especially leukocytes
Multiply within membrane-bound structures called morulea within the cells (they are dark spots within the cells)

Question 25

Anaplasmataceae vectors

Answer 25

Lone star tick and blacklegged tick

Question 26

Ehrlichia chafeensis epidemiology

Answer 26

Worldwide distribution
SE to SCentral USA
White-tailed deer reservoir
Lone star tick vector

Question 27

Ehrlichia chafeensis disease

Answer 27

Incubation 5-21d
SSx: fever, headache, myalgia, rash
Complications: CNS, meningitis, renal failure, myocarditis

Question 28

A. phagocytophilum epidemiology

Answer 28

Worldwide, upper midwest and NE states
Reservoir: wild rodents
Vector: blacklegged ticks

Question 29

A. phagocytophilum disease

Answer 29

Incubation 7-14d
SSx: fever, headache, myalgia, rash
Complications: ARDS, renal failure, TSS, myocarditis, serious opportunistic infections (from low leukocyte counts)

Question 30

Diagnosing ehrlichioses and anaplasmosis

Answer 30

History, area, blood tests–leukopenia, low platelets, MURULAE in stained leukocytes

Question 31

ehrlichioses and anaplasmosis treatment

Answer 31

Doxycycline or rifampin