Lyme and Ehrlichia

Question 1

What age groups are most often affected by Lyme disease?

Answer 1

bimodal distribution: children aged 5-14 and adults aged 55-70 years

Question 2

What is the causative agent of Lyme disease

Answer 2

Borrelia burgdorferi, a spirochete

Question 3

A wide array of ______ help B. burgdorferi adapt to mammalian and arthropod hosts

Answer 3

outer surface proteins

Question 4

The only known virulence factor of B. burgdorferi are _____

Answer 4

lipoproteins

no known toxins

Question 5

What tick is responsible for the transmission of Lyme disease?

Answer 5

Ixodes scapularis in NE and central US
can also transmit anaplasmosis (HGA) and babesiosis

Ixodes pacificus in Pacific US
can also transmit anaplasmosis (HGA)

Question 6

Tick larvae emerge in the _____ and take a blood meal, usually from a bird or small mammal

Answer 6

spring/ early summer

if animal is infected, tick becomes infected

Question 7

Humans are most likely to be infected with Lyme by a tick in the ____ stage of development

Answer 7

nymph

or adult, not larvae- have not yet taken a blood meal

Question 8

Why are adult ticks less likely to transmit Lyme to a human?

Answer 8

More likely to be noticed and removed

Question 9

List factors that determine the risk of infection in humans in a given region

Answer 9

Tick density
Tick feeding habits
Proportion of ticks infected
Animal host availability- important in maintaining B burgdorferi in the environment
Amount of time spent outdoors during tick season

Question 10

How long is B burgdorferi incubation period?

Answer 10

7-14 days

Question 11

Describe the early localized stage of Lyme disease

Answer 11

7-14 day incubation period then rash develops
Erythema migrans at the site of the tick bite, usually thigh, buttock, groin, axilla
Non-specific constitutional symptoms

Question 12

Describe early disseminated stage of Lyme disease

Answer 12

Days to weeks after infection
Multiple secondary erythema migrans lesions
MSK- migratory joint pain, muscle pain
Neurologic- meningitis, facial nerve paralysis, radicular neuropathy
CV- new onset AV block
ocular involvement

Question 13

Describe the late disseminated stage of Lyme disease

Answer 13

Months after infection
intermittent large joint arthritis
encephalopathy w/ cognitive and personality changes
spastic paresis, ataxia, fatigue

Question 14

A single dose of doxycycline can be given as prophylaxis for tick bites if:

Answer 14

• attached tick identified as nymph or adult Ixodes scapularis, has been present for >24 hours
• prophylaxis within 72 hours of removal
• local tick infection rate >20%
• no contraindications to doxycycline

Question 15

Describe the CSF profile of a person with Lyme meningitis

Answer 15

aseptic meningitis profile with lymphocytes in the CSF, normal glucose and elevated protein

Question 16

List complications of Lyme disease

Answer 16

Lyme meningitis
Lyme carditis
Lyme arthritis
Post-Lyme disease syndrome

Question 17

What is the appropriate treatment for Lyme with nervous or cardiac involvement?

Answer 17

ceftriaxone

Question 18

Lyme arthritis may persist despite antibiotics, and is then thought to be ______ in nature

Answer 18

autoimmune

Question 19

How is Lyme disease diagnosed?

Answer 19

In early localized infection, it is a clinical diagnosis- antibodies will be negative
2 step testing is recommended- ELISA then Western blot

Question 20

Lyme serology cannot distinguish ____ from ____ infection

Answer 20

past from active

Question 21

What antibiotic is usually used to treat Lyme disease?

Answer 21

Doxycycline
Amoxicillin or cefuroxime if pregnant, lactation, children
Ceftriaxone for neurologic involvement, AV block, recurrent arthritis

Question 22

Distinguish human granulocytic anaplasmosis from human monocytotropic ehrlichiosis

Answer 22

Human granulocytic anaplasmosis (HGA)
- Caused by Anaplasma phagocytophilum; found in granulocytes
- Distribution and risks mimic Lyme disease because of the shared tick vector, Ixodes scapularis. In the west, it is spread
by Ixodes pacificus.
- Animal reservoir is white tailed deer

Human monocytotropic ehrlichiosis (HME)
- Caused by Ehrlichia chaffeensis; found in monocytes
- Distribution mostly S Central and SE US because of the distribution of the
primary tick vector, Amblyomma americanum (the Lone Star tick)
- Animal reservoir is white tailed deer

Question 23

Both anaplasmosis and erhlichiosis organisms are _______ bacteria with tropism for leukocytes

Answer 23

obligate intracellular

Question 24

What is a morulla?

Answer 24

Ehrlichia or anaplasmosis organisms grouped together within cytoplasmic vacuoles in infected cells

Question 25

Describe the clinical symptoms of Ehrlichia

Answer 25

fever, headache, myalgia, malaise
NV, arthralgia, cough, mental status change
rash: maculopapular > petechial
if severe: shock, hemorrhage, ARDS

Question 26

Describe the lab findings in Ehrlichia

Answer 26

low platelets 
low WBCs
anemia (slow decline)
high ALT/AST
high creatinine

Question 27

Describe the pathogenesis of ehrlichia

Answer 27

Tick bite–> organisms disseminate to the bone marrow and reticuloendothelial organs then attach to and infect granulocytes (HGA) or monocytes/ macrophages (HME)
Can find non-caseating, necrotizing granulomas in the bone marrow and reticuloendothelial organs
Host inflammatory response is the cause of much of the end organ pathology

Question 28

In general, there is less CNS disease and lower mortality in ____ and rash is more common in _____

Answer 28

HGA

HME

Question 29

What is appropriate treatment for ehrichia

Answer 29

Doxycycline 10-14 days, start BEFORE lab diagnosis is made

Improvement will be rapid once doxycycline is started