Vector-borne bacterial infections

Question 1

Which bacterial species causes Rocky Mountain Spotted Fever (RMSF)?

Answer 1

Rickettsia Rickettsii, a weekly / non-staining Gram negative bacillo-cocci (oval).

Question 2

What is the vector for the bacteria causing Rocky Mountain Spotted Fever?

Answer 2

The Tick (Dermacentor)

Question 3

What bacterial species causes (epidemic) Typhus?

Answer 3

Rickettsia prowazekii, a weekly / non-staining Gram negative bacillo-cocci (oval).

Question 4

What is the vector for the bacteria causing Typhus?

Answer 4

The human louse.

Question 5

What bacteria causes Rickettsial pox?

Answer 5

Rickettsia akari

Question 6

What is the vector and reservoir for Rickettsial pox?

Answer 6

Mites are the vector and mice the reservoir.

Question 7

What is the clinical presentation of Rickettsial pox?

Answer 7

1) Bite -> nodule / papule.
2) Flu-like symptoms.
3) Rash
4) Bite becomes necrotic eschar.

Question 8

1) What is the treatment for all Rickettsial diseases ?

2) Which disease is most lethal and which does not require treatment?

Answer 8

1) Doxycycline.
2) RMSF can be lethal within a week, do not wait for confirmed diagnosis. Treat upon suspicion. Rickettsial pox however usually goes away on its own.

Question 9

What do “flu-like symptoms” between Spring and Fall suggest?

Answer 9

These symptoms suggest a Rickettsial disease.

Fever, headache, chills, myalgias, etc.

Question 10

What symptom is highly suggestive of RMSF?

Answer 10

A rash that covers palms and soles and spreads from periphery inwards.

Question 11

What symptom suggests Typhus?

Answer 11

A rash that spreads outwards from the core.

Question 12

What lab findings are characteristic of Rickettsial disease?

Answer 12

Thrombocytopenia, high LTFs, neutropenia, hyponatremia (low Na).

Question 13

What is the main pathogenic mechanism of Rickettsia rickettsii?

Answer 13

Vasculitis (endothelial damage) causes rash, petechiae, purpura, and leads to multi-organ system failure.

Question 14

What are the two forms of Ehrlichioses?

What bacteria causes them?

Answer 14

Human Monocytic Ehrlichiosis (Erhlichia chaffeensis)

Human Granulocytic Anaplasmosis (Anaplasma phagocytophilum)

Question 15

What is a characteristic finding under a microscope of a leukocyte (either granulocyte or monocyte) infected with HME or HMA?

Answer 15

An intracellular “morulae” or mulberry cluster of Erhlichia chaffeensis or Anaplasma phagocytophilum.

Question 16

What is the vector for the Ehrlichioses?

Answer 16

The ixode tick

Question 17

Treatment for Anaplasmosis and Ehrlichiosis?

Answer 17

Doxycycline

Question 18

What does a halo shaped rash (erythematous ring called Erythema migrans) around a nodule/papule/bite suggest?

Answer 18

Lyme disease.

Question 19

What is the bacteria responsible for Lyme disease and what is its vector?

Answer 19

Borrelia burgdorferi is a gram-negative spirochete carried by the Ixode tick and causes Lyme.

Question 20

Why do “tick checks”?

Answer 20

Because the tick must be attached (feeding) for 24hrs in order to transmit Borrelia burgdorferi.

Question 21

What are the stages of Lyme disease?

Answer 21

1) Early localized - erythema migrans.
2) Early disseminated - Bell’s palsy (CN VII), meningitis, arthritis, heart block, pericarditis.
3) Late disseminated - Migratory polyarthritis, encephalopathy, meningitis.

Question 22

What stains can be used to visualize Borrelia burgdorferi?

Answer 22

Wright’s stain or Giemsa stain.