27 - 180 - THE RICKETTSIOSES, EHRLICHIOSES, AND ANAPLASMOSES

Question 1

most frequently reported rickettsial infection in the United States

Answer 1

Rocky Mountain Spotted Fever (RMSF)

Question 2

vector largely responsible for RMSF in the eastern two-thirds of the United States

Answer 2

American dog tick, Dermacentor variabilis

Question 3

triad of Rocky Mountain Spotted Fever (RMSF)

Answer 3

1. fever (>39.5°C [102°F]),
2. headache,
3. rash

but only approximately 60% of patients will have the complete clinical triad

Question 4

gold standard for diagnosis of RMSF

Answer 4

Serologic examination using the indirect immunofluorescence assay (IFA)

Question 5

An effective treatment of RMSF should begin by what day of illness?

Answer 5

fifth day

Question 6

drugs of choice for all rickettsial diseases in patients of all ages, even during pregnancy

Answer 6

Tetracyclines, specifically doxycycline

Question 7

Answer 7

ROCKY MOUNTAIN SPOTTED FEVER

Question 8

Answer 8

HUMAN MONOCYTIC EHRLICHIOSIS

Question 9

Answer 9

HUMAN GRANULOCYTIC ANAPLASMOSIS

Question 10

may be used if tetracyclines are contraindicated because of allergies

Answer 10

Chloramphenicol

Question 11

most important factor affecting survival

Answer 11

Prompt empiric administration of appropriate antibiotic therapy

Question 12

causative agent of Mediterranean spotted fever (MSF)

Answer 12

Rickettsia conorii

transmitted by an infected R. sanguineus tick

Question 13

The classic cutaneous hallmark of Mediterranean spotted fever (MSF)

Answer 13

tache noir

The tache noir occurs at the site of inoculation as an erythematous, indurated papule with a central necrotic eschar that represents locally aggressive endothelial invasion by rickettsiae

Question 14

Rickettsialpox is an acute, self-limited, febrile disease so named because of its clinical resemblance to varicella (chickenpox).

What is its etiologic agent?

What is the vector and its reservoir?

Answer 14

Rickettsia akari

• Vector: rodent mite, Liponyssoides sanguineus (formerly Allodermanyssus sanguineus)
• Reservoir: Mus musculus, the house mouse

Question 15

Question 16

Management of Rickettsial, Ehrlichial, and Anaplasma Infections

Answer 16

Question 17

The preferred method to identify causative agent in rickettsialpox

Answer 17

swabbing eschar or vesicles of patients with rickettsioses allowing DNA detection by PCR

The use of multiplex real-time PCR offers greater sensitivity than nested PCR assays to distinguish various rickettsial species.

Question 18

1. causative agent of Endemic/ Murine/ Flea-borne typhus
2. What is the vector and its reservoir?

Answer 18

1. Rickettsia typhi
2. rat flea (Xenopsylla cheopis); rats

Question 19

This agent has emerged as an important agent of endemic typhus with characteristics of both the typhus and spotted fever group rickettsiae.

Answer 19

Rickettsia felis

Question 20

1. Causative agent of Epidemic/ Louse-Borne typhus
2. What is the vector and reservoir?

Answer 20

1. Rickettsia prowazekii
2. body louse (Pediculus humanus var. corporis); humans

The centrifugal spread, lack of eschar, and predilection for colder months helps differentiate epidemic typhus from other rickettsial infections

Question 21

A reemergence of the illness known as Brill–Zinsser disease (BZD) can occur in survivors who may suffer recrudescent infection, even decades after the initial infection.

Answer 21

Epidemic typhus (also called prison fever, famine fever, and ship fever)

BZD occurs as a recrudescence of previous infection with R. prowazekii

Question 22

causative agent and vector of Human granulocytic Anaplasmosis (HGA)

Answer 22

1. Anaplasma phagocytophilum
2. Ixodes Tick

Question 23

E. chaffeensis is trophic to what cells?

Answer 23

monocytic cells

Question 24

A. phagocytophilum is trophic for what cells?

Answer 24

myeloid or granulocytic cells