Lyme and Ehrlichia Flashcards Preview

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Flashcards in Lyme and Ehrlichia Deck (29):

What age groups are most often affected by Lyme disease?

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


What is the causative agent of Lyme disease

Borrelia burgdorferi, a spirochete


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

outer surface proteins


The only known virulence factor of B. burgdorferi are _____

no known toxins


What tick is responsible for the transmission of Lyme disease?

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

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


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

spring/ early summer
if animal is infected, tick becomes infected


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

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


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

More likely to be noticed and removed


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

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


How long is B burgdorferi incubation period?

7-14 days


Describe the early localized stage of Lyme disease

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


Describe early disseminated stage of Lyme disease

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


Describe the late disseminated stage of Lyme disease

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


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

- 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


Describe the CSF profile of a person with Lyme meningitis

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


List complications of Lyme disease

Lyme meningitis
Lyme carditis
Lyme arthritis
Post-Lyme disease syndrome


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



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



How is Lyme disease diagnosed?

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


Lyme serology cannot distinguish ____ from ____ infection

past from active


What antibiotic is usually used to treat Lyme disease?

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


Distinguish human granulocytic anaplasmosis from human monocytotropic ehrlichiosis

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


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

obligate intracellular


What is a morulla?

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


Describe the clinical symptoms of Ehrlichia

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


Describe the lab findings in Ehrlichia

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


Describe the pathogenesis of ehrlichia

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


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



What is appropriate treatment for ehrichia

Doxycycline 10-14 days, start BEFORE lab diagnosis is made
Improvement will be rapid once doxycycline is started