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ICM > 2: tickborne diseases > Flashcards

2: tickborne diseases Flashcards

1
Q

3 major diseases, organisms, and ticks

A
  1. Lyme disease - Borrelia burgdorferi (ixodes tick/deer tick)
  2. RMSF - Rickettsia rickettsii (american dog tick)
  3. human monocytotropic ehrlichiosis - Ehrlichia chaffeensis (lone star tick)
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2
Q

what type of organism is Borrelia burgdorferi

A

spirochete

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3
Q

vector of Lyme disease

A
  • ixodes tick (hard-bodied tick)

- blacklegged tick/deer tick = sole vector in hyperendemic regions of eastern US

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4
Q

sx/signs of stage 1 Lyme disease

A
  • localized (incubation 3-32d)

- rash (erythema migrans)

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5
Q

sx/signs of stage 2 Lyme disease

A
  • disseminated
  • multiple annular skin lesions
  • meningitis (headache, fever, stiff neck)
  • cranial neuritis (CN7 - facial hemiparesis)
  • carditis (AV block)
  • arthralgia
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6
Q

sx/signs of stage 3 Lyme disease

A
  • persistent
  • oligoarticular arthritis (knee joints)
  • encephalopathy (mood, memory, sleep disturbance)
  • axonal polyneuropathy (tingling feet, weakness)
  • acrodermatitis (skin changes on hands and feet)
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7
Q

describe erythema migrans

A

target “bull’s eye” rash with central clearing and potentially a necrotic center/vesicular lesions
-blanching rash!

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8
Q

differential diagnosis of CN7 palsy

A
  • idiopathic (Bell’s palsy)
  • lyme disease
  • HSV (usually no rash)
  • Herpes zoster/ Ramsay Hunt syndrome (vesicles in external auditory canal)
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9
Q

describe post-lyme disease “chronic lyme disease”

A
  • pain syndrome (arthralgias)
  • chronic fatigue
  • neurocognitive symptoms

-sx occur for years after eradication of infection

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10
Q

what can sx of chronic lyme disease be confused with?

A

chronic fatigue syndrome - fibromyalgia

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11
Q

serologic testing for lyme disease

A

IgM and IgG - often retrospective diagnosis using paired sera (acute and convalescent, draw at presentation and 2-4 weeks later)
*better results from 2-4 weeks later

ELISA with Western blot verification - similar to older HIV testing methods

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12
Q

other ways to diagnose lyme disease besides serologic testing

A
  • PCR of joint fluid from arthrocentesis done in patient with arthritis
  • PCR of CSF (but has low sensitivity)
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13
Q

if a patient is high risk/ highly worried about lyme disease, what should you do?

A

draw sera at time of presentation
empirically start them on doxy
then draw sera at 2-4 weeks again

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14
Q

short answer for treatment of lyme disease

A

doxycycline!

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15
Q

vaccine for lyme disease?

A

not for humans (there is a canine vaccine)

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16
Q

name some tick prevention methods

A
  • examine self after potential exposure, remove ticks
  • use insecticides with DEET
  • tuck pants into socks
  • pre-treat clothes with permethrin insecticides
  • insect shield clothing
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17
Q

causative organism of RMSF

A

rickettsia rickettsii

  • small, obligate intracellular
  • G(-) bacilli
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18
Q

trophism of rickettsia rickettsii

A

for vascular endothelial cells

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19
Q

RMSF vector

A

american dog tick in eastern US

20
Q

incubation for RMSF

A

about 1 week

21
Q

basic pathophysiology of RMSF

A

(vasculitis)
- increased vascular permeability
- edema, hypovolemia
- hyponatremia d/t compensatory ADH release
- thrombocytopenia

-DIC is rare

22
Q

clinical presentation of RMSF

A

classic triad: fever, rash, history of tick exposure***

symptoms:
- fever
- headache
- myalgia
- malaise

23
Q

describe progression of rash of RMSF

A
  • starts as faint macules
  • progresses to vasculitic rash w/ non-blanching petechiae
  • may involve palms and soles
24
Q

if you have someone who has faint rash, but not sure if RMSF or not, where is another place you can look for petechiae?

A

axillary folds

25
Q

sx of progressing RMSF

A
  • hypovolemia
  • hypotension
  • fluid third spacing
  • respiratory failure
  • cardiac dysrhythmia
  • CNS symptoms - confusion, lethargy, encephalopathy
  • ATN (acute tubular necrosis)
  • shock
  • elevated transaminases- acute hepatitis/liver failure
26
Q

diagnosis of RMSF

A
  • clinical presentation
  • risk for or history of tick exposure
  • lab testing
27
Q

lab testing for RMSF

A
  • thrombocytopenia (low platelets)
  • hyponatremia (low sodium)
  • azotemia (increased BUN, potentially increased Cr if ATN develops)
28
Q

R. rickettsii testing

A
  • no completely reliable test in early stages of disease
  • skin biopsy w/ direct immunofluorescence staining (obtain before or w/i 12h of antibiotic therapy)
  • serologic testing of IgM and IgG (first set after 5d of illness, second set 14-21d after symptom onset)
29
Q

differential diagnosis of patient w/ fever, petechial rash on palms and soles, potential tick exposure

A
  • meningococcal disease
  • tick-borne disease RMSF
  • enterovirus
  • secondary syphilis
  • rubella
  • drug eruption
  • Kawasaki disease
  • Coxsackie virus (hand foot and mouth disease)
30
Q

what would you do when a patient w/ fever, petechial rash on palms and soles, and potential tick exposure comes in?

A
  • obtain blood and consider CSF
  • consider skin biopsy
  • empiric therapy for both meningococcal disease and RMSF
    • **ceftriaxone and doxycycline
31
Q

why is it important to treat early with RMSF?

A

delay in treatment (more than 5d past onset of sx) associated with increased risk of mortality

32
Q

what are 3 factors that are independent predictors of failure of clinician to initiate anti-rickettsial therapy?

A
  1. absence of skin rash
  2. presentation w/i the first 3 days of illness
  3. presentation b/w Aug 1 and Apr 30 (not tick season)
33
Q

treatment of RMSF

A

**doxycycline! (except preggers - chloramphenicol)

34
Q

potential side effect of doxycycline in kids

A

can cause dental staining in kids

35
Q

chloramphenicol

A

-RMSF treatment of choice for pregnant women
BUT problems:
-difficult to obtain
-less effective
-in some cases benefits of doxycycline outweigh risks in pregnancy

36
Q

causative organism of ehrlichiosis

A

ehrlichia chaffeensis (obligate intracellular organism)

37
Q

vector of ehrlichiosis

A

lone star tick

38
Q

incubation period of ehrlichiosis

A

~8d

39
Q

sx of ehrlichiosis

A
  • fever
  • headache
  • myalgias

disease ranges from mild to severe

40
Q

lab findings of ehrlichiosis

A
  • leukopenia
  • thrombocytopenia (low platelets)
  • elevated transaminases
41
Q

treatment for ehrlichiosis

A

doxycycline!

42
Q

distribution of ehrlichiosis

A

more southeast US

43
Q

how can you differentiate RMSF from ehrlichiosis?

A
  • RMSF infects endothelial cells -> vasculitis (rash)

- ehrlichiosis infects phagocytes -> rash much less common

44
Q

how do you identify a tick when it is engorged?

A

check the scutum (shield) - the typical pattern will still be visible despite the size of the engorged body

45
Q

recommended way to remove a tick

A
  • use a pair of tweezers and find where tick’s mouthparts have entered skin
  • place ends of tweezers around base of mouthparts and while applying gentle pressure, pull the tick up slowly and steadily until it releases its hold
  • dispose of the tick in a sealable plastic bag in the trash outside your home
46
Q

what are things to not do when removing a tick?

A
  • do not twist, poke, squash, or burn the tick

- do not smother the tick with any substance

ICM (26 decks)

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