Tick Borne Infections

Question 1

Rickettsial Pathogens

Answer 1

Small, pleomorphic Gram negative coccobacilli
Obligate INTRAcellular bacteria
Zoonoses via arthropod intermediate
Non-motile (no flagella) but do have actin based motility

Question 2

3 pathogens that have actin based motility

Answer 2

Listeria
Shigella
Rickettsia

Question 3

Endemic vs epidemic typhus host

Answer 3

En: fleas
Epi: lice

Question 4

Orientia tsutsugamushi
(what does it cause, where is it found, reservoir, vector, main symptoms)

Answer 4

Scrub typhus
Similar to other forms of typhus
Endemic in india, south east asia, australia
Reservoir: rodents
Vector: trombiculid mite (chigger)
Main symptoms: morbilliform rash, hemorrhage and intravascular coagulation (systemic disease)

Question 5

What pathogens cause a morbilliform rash?

Answer 5

Measles
Rubella
Roseola
Scrub typhus
Rickettsia prowazekii

Question 6

EPIdemic typhus

causative agent, transmission, vector, reservoir, epidemics or sporadic

Answer 6

Rickettsia prowazekii
Transmitted person to person
Vector is human body lice
Causes epidemics- from poor sanitation/crowding
Reservoir is humans
More severe manifestation

Question 7

ENdemic typhus

causative agents, transmission, vector, reservoir, epidemics or sporadic

Answer 7

Rickettsia typhi and R. felis
No person to person transmission
Vector is rat flea - from bite or feces
Cases are sporadic
Reservoir is rodents
Usually milder

Question 8

Rocky Mountain Spotted Fever

Answer 8

Rickettsia produces a vasculitis throughout the body
Symptoms can be highly variable
Rash starts on extremities and moves inward
Have to treat right away

Question 9

Difference in rash between RMSF and Typhus

Answer 9

RMSF: centripetal progression (starts on extremities, and then to trunk)
Typhus: centrifugal progression (starts on trunk and then moves out)

Question 10

Where is Dermacentor andersoni vs Dermacentor variabilis found in the US?

Answer 10

andersoni: west coast
variabilis: east coast

Question 11

Rickettsial disease treatment

Answer 11

Should be empiric!

Doxycycline

Question 12

Best way to diagnose rickettsial diseases

Answer 12

Serology - but by the time you’ve mounted an immune response its too late (have to treat first)
Can also do PCR
Or DFA but need good biopsy of endothelium

Question 13

Lyme disease

causative agents, morphology, vector

Answer 13

Borrelia burgdorferi
Gram negative spirochete
Vector is Ixodes ticks

Question 14

Where is Ixodes scapularis vs Ixodes pacificus found?

Answer 14

scap: Central/eastern
paci: western

Question 15

Lyme disease reservoir and preferred host

Answer 15

Res: white footed mouse
PH: white-tailed deer

Question 16

What disease does not have transovarian transmission?

Answer 16

Lyme disease

Question 17

What is a good diagnostic clue for early Lyme disease

Answer 17

Eryhtemia migrans = bull’s eye rash

Anywhere in the skin

Question 18

2 tiered testing for Lyme disease

Answer 18

1. ELISA (IgG/IgM) screen: very sensitive, but not specific
2. Western Blot (IgM and IgG): very specific but not sensitive
   Need 5-10 bands for IgG and 3-5 for IgM to be positive

Question 19

Babesiosis

caused by, vector, reservoir, treatment

Answer 19

Caused by a parasite that infects RBCs
Most human cases are caused by Babesia microti
Vector: Ixodes ticks
Reservoir: white footed mouse
Treatment: clindamycin/quinine, atovaquone/azithromycin

Question 20

Babesia vs Plasmodium

Answer 20

Babesia is smaller, and there could be multiple ring forms inside the RBCs