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Infectious Disease > Tick-borne Disease > Flashcards

Tick-borne Disease Flashcards

1
Q

what is questing behavior?

A
  • ticks wander about the skin of the host for several hours before attaching
  • larvae detect heat, movement and CO2
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2
Q

timing of tick disease transmission

A

-usu takes 24-48 hrs of attachment and feeding before transmission

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3
Q

what % of tick bites result in tick-borne infection?

A

1%

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4
Q

contents of tick saliva

A
  • neurotoxins
  • anticoagulants
  • immunosuppressants
  • anti-inflammatories
  • pathogens: bacteria, viruses, nematodes
  • toxins
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5
Q

RFs for ticks

A
  • male
  • children
  • farmers
  • exposure to dogs
  • live in wooded area
  • exposure!!!
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6
Q

RMSF classic presentation

A
  • high fever
  • HA
  • petechial rash w/ hx of tick bite
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7
Q

RMSF mortality rate

A

if untreated, 30% mortality rate

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8
Q

rickettsia rickettsii

A
  • gram neg. bacteria
  • obligate intracellular parasite w/ tropism for human endothelial cells
  • transmitted to humans through saliva while a tick is feeding
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9
Q

mechanism of injury in RMSF

A
  • tick attached for many hours
  • r. rickettsii enter skin
  • spread via lymph to blood stream
  • live inside vascular endothelial cells and multiply
  • endothelial cells die, allowing blood to leak out of vessels into surrounding tissues
  • sm. vessel thrombi and obstruction, fluid leakage causing edema, hypovolemia and low BP
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10
Q

S/Sx of RMSF

A
  • sudden onset
  • fever
  • malaise
  • severe frontal HA
  • myalgia
  • vomiting

(flu like so hard to diagnose)

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11
Q

RMSF incubation period

A

2-14 days (avg. 7)

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12
Q

RMSF rash

A
  • 90% of pts get it - usu 3-5 days after bite
  • blanching erythematous rash w/ macules that become petechial over time
  • starts on wrists and ankles and spreads to trunk
  • rash on palms and soles is characteristic but not present until later dz
  • can be easily missed in dark skin
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13
Q

Ddx of RMSF

A
  • viral illness
  • drug allergy
  • measles
  • meningococcemia
  • mono
  • roseola
  • fifth dz
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14
Q

lab detection of early RMSF

A

-nothing available for early RMSF –> dx based on clinical suspicion

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15
Q

clinical findings suggestive of RMSF

A
  • thrombocytopenia: from increased destruction at sites of rickettsia mediated vascular injury
  • elevated LFTs
  • hyponatremia (50% of pts) d/t hypovolemia
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16
Q

rickettsial indirect fluorescent antibody (IFA) serum test

A
  • recommended by CBC
  • detects Abs in blood samples
  • diagnostic Ab levels don’t appear until 7 days after onset
  • confirmation = 4 fold change in titers
  • Abs may persist for years
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17
Q

immunostaining for RMSF

A
  • 3 mm punch bx of rash taken prior or w/i first 48 hrs after abx therapy
  • not recommended by CBC - only 70% sensitive
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18
Q

Tx timing for RMSF

A
  • DON’T delay tx for lab results or rash

- treat immediately if true suspicion

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19
Q

pharmacological tx for RMSF

A
  • doxycycline 100 mg BID 3 days or more after fever subsides (min. 5-10d)
  • failure to respond suggests wrong dx
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20
Q

outpatient vs. inpatient tx of RMSF

A
  • outpatient: if mildly ill

- hospital: severely ill, complications, may take up to 5 days to become afebrile

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21
Q

important ADRs of doxycycline

A
  • esophagitis (take w/ full glass of water)
  • teeth discoloration: don’t use in kids < 8 yo
  • photosensitivity
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22
Q

Complications of RMSF

A
  • DIC
  • skin necrosis
  • cardiac arrythmias
  • encephalitis
  • GI bleed
  • death w/o tx
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23
Q

what is the MC tick borne dz in the US and Europe?

A

lyme dz

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24
Q

bacteria in lyme dz

A

borrelia burgdorferi (spirochete)

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25
Q

tick vector for lyme dz

A
  • deer tick (ixodes scapularis)
  • most likely to transmit infection after feeding for 2 or more days
  • reservoir is white tailed deer
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26
Q

tick vector for RMSF

A
  • american dog tick (dermacentor variabilis) - in Eastern and South Central US
  • rocky mt wood tick (dermacentor andersoni) - in mountain states west of the mississippi
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27
Q

pathophysiology of lyme dz

A
  • borrelia in tick midgut –> salivary glands –> host

- then spirochetes disseminate from the bite site

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28
Q

3 ways spirochetes disseminate from bite site in lyme

A
  • cutaneous - travel centrifugally
  • lymphatic
  • hematogenous routes
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29
Q

S/sx of lyme dz

A
  • many feel mildly ill
  • myalgia
  • arthralgias
  • fatigue
  • neck stiffness
  • low grade fever
  • regional adenopathy
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30
Q

halmark of lyme dz

A

erythema migrans

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31
Q

erythema migrans

A
  • slowly expanding bulls eye rash
  • 40% have central clearing
  • usu not painful or itchy
  • common sites: popliteal fossa, gluteal fold, torso, axilla
  • avg size: 15 cm
  • if untreated, resolves in 3-4 weeks
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32
Q

early localized stage of lyme infection

A
  • days to a month after infection

- erythema migrans and viral-like sx

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33
Q

early disseminated stage of lyme infection

A
  • weeks to months after infection
  • neurologic sequalae (facial palsy, meningitis)
  • cardiac dz (conduction deficits, blocks)
  • severe malaise
34
Q

late stage of lyme infection

A
  • months to yrs after infection
  • migratory arthritis pain and swelling in asymmetric large joints (usually knee)
  • cognitive deficits
  • usu resolves w/i a few weeks or months of abx
  • acrodermatitis chronica atrophicans (not really in US )
35
Q

summary of sx of lyme

A

skin, joints, nervous, cardiac sx

36
Q

Ddx of lyme dz

A
  • changing mole
  • cellulitis
  • tinea
  • granuloma annulare
  • fixed drug erruption
  • contact dermatitis
  • spider bite
37
Q

dx of lyme dz

A

-erythma migrans + pt present in endemic area
OR
-serology + extracutaneous manifestations of lyme dz

38
Q

Lab detection of lyme dz

A
  • ELISA or IFA

- if positive then western blot test for corroboration

39
Q

tx of lyme dz

A
  • doxycycline 100 mg BID

- duration depends on stage of dz

40
Q

alternative tx for lyme dz

A
  • amoxicillin 500 mg TID x 14 days

- cefuroxime 500 mg BID x 14 days

41
Q

jarisch-herxheimer rxn

A
  • rapid destruction of organisms w/ release of membrane into circulation
  • intesification of sx w/ tachycardia and hypotension
  • 12-24 hrs after treatment
  • pts can confuse w/ allergic rxn
42
Q

relapsing fever

A
  • from bite of tick or louse infected w/ Borrelia

- rare

43
Q

common location for relapsing fever

A

-associated w/ sleeping in rustic cabins in mountainous areas of western US, canada, africa, europe

44
Q

sx of relapsing fever

A
  • HA, muscle and joint aches and nausea

- recurrent, acute episodes of fever (up to 106) followed by periods of defeverscence of increasing duration

45
Q

Dx of relapsing fever

A

-observation of Borrelia in blood smear, spinal fluid, or bone marrow of a symptomatic person

46
Q

southern tick-associated rash illness (STARI)

A
  • lyme like dz in southeaster and south central states

- not fully characterized

47
Q

STARI tick vector

A
  • ambylomma americanum (lonestar tick)
  • aggressively bites humans
  • unknown cause
48
Q

sx of STARI

A
  • erythema migrans w/i 7 days of bite; > 8cm
  • mild clinical course: fatigue, fever, HA, muscle and joint pain
  • NOT linked to chronic arthritic or neurologic sx
49
Q

lab eval and tx of STARI

A
  • lab: negative lyme test; no commercially available test

- tx: doxycycline 100 BID x 10 days

50
Q

causative agent of ehrlichiosis

A

-ehrlichia chaffeensis: small gram negative bacteria that primarily invade leukocytes (monocytic)
AND
-anaplasma phagocytophilum (granulocytic)

51
Q

ehrlichiosis tick vector

A
  • lone star tick; amblyomma americanum (HME)
  • blacklegged tick; ixodes scapularis (HGA)
  • western blacklegged tick; ixodes pacificus
52
Q

Hosts for ehrlichiosis

A
  • coyotes
  • mouse
  • white-tailed deer
  • horses (in OK)
53
Q

pathophys of ehrlichiosis

A

bacteria infect either monocytes (HME) or granulocytes (HGA)

54
Q

what is a characteristic of ehrlichiosis?

A

-morulae: bacteria divide w/i vacuoles inside leukocytes to form morulae

55
Q

s/sx of ehrlichiosis

A
  • hx of a tick bite
  • most pts are asx
  • incubation of 1-2 weeks
  • rash is rare
  • fever/HA
56
Q

lab findings in ehrlichiosis

A
  • leukopenia
  • thrombocytopenia
  • elevated LFT, LDH, and alkaline phosphatase
  • indirect fluorescent antibody test is preferred diagnostic method
57
Q

Ddx of ehrlichiosis

A

RMSF

58
Q

complications of ehrlichiosis

A
  • usually in immunocomrpomised
  • renal failure
  • disseminated intravascular coagulopathy
  • meningoencephalitis
  • adult respiratory distress syndrome
  • seizures
  • coma
59
Q

tx of ehrlichiosis

A
  • tx should not be delayed for labs

- doxycycline 100 BID x 10 days or for 3-5 days after defervescence

60
Q

mortality in ehrlichiosis

A

-HME: 2-5%
-HGA: 7-10%
(probably overestimations)

61
Q

tularemia (aka rabbit fever) bacteria

A
  • francisella tularensis

- gram negative bacteria

62
Q

tularemia tick vectors

A
  • american dog dick: dermacentor variabilis

- lone star tick; amblyomma americanum

63
Q

hosts for tularemia

A

rodents and rabits

64
Q

epidemiology of tularemia

A

avg. 25 cases/yr in OK

65
Q

how to become infected w/ tularemia

A

-begin bitten by infected tick (MC), deerfly or other insect
-handing infected animal carcasses
-cat scratch or bite
-eating/drinking contaminated food/water
-inhalation
(not person to person)

66
Q

clinical presentation of tularemia

A
  • usu in 3-5 days
  • ranges from asx to septic shock and death
  • the type is based on mechanism of entry of the organism
67
Q

ulceroglandular type of tularemia

A
  • 80%
  • bacteria enters through scratch, tick bite, or abrasions
  • fever, ulcer, lymphadenopathy
68
Q

glandular type of tularemia

A
  • similar to ulceroglandular but no skin lesion

- organism is presumed to enter via inapparent abrasion and then spreads

69
Q

oculoglandular type of tularemia

A
  • organism enters via conjunctiva of the eye (by splashing of blood or rubbing eyes)
  • 1-2%
  • painful, purulent conjunctivitis w/ preauricular or cervical lymphadenopathy
70
Q

oropharyngeal type tularemia

A
  • 1-4%
  • after eating poorly cooked meat of an infected rabbit or drinking contaminated water
  • sore throat, abd pain, n/v/d, occasionally frank GI bleed
71
Q

pneumonic type tularemia

A
  • from either inhalation or hematogenous spread
  • MC in lab workers
  • dry cough, dyspnea, and pleuritic chest pain
  • can get pneumonia and/or ARDS
72
Q

typhoidal type tularemia

A
  • 10-15%
  • more severe
  • likely from bacteremia
  • fever, chilles, myalgias, malaise, weight loss
  • often present w/ pneumonia
73
Q

dx of tularemia

A
  • culture of organism from blood, sputum, wound (have to culture in cysteine)
  • serology: 1:160 or higher titer is positive
74
Q

tx of tularemia

A

-streptomycin 10mg/kg BID (IM) x 7-10 days

75
Q

prognosis of tularemia

A
  • mortality in untreated: 5-15%

- mortality in treated: < 4%

76
Q

bioweapon potential of tularemia

A
  • widely found in nature and relative easy to grow in lab
  • used airborne, easy to spread
  • highly infectious
  • so vaccine is available for those at high risk
77
Q

tick paralysis

A
  • rare, but can be fatal
  • removal of tick will usu begin recovery w/i hours
  • female tick saliva contains neurotoxins that result in paralysis (localized to bodywide)
78
Q

ticks implicated for tick paralysis

A
  • dermacentor
  • ixodes
  • amblyomma
  • usually attached 4-7 days before paralysis occurs
79
Q

red meat allergy tick vector

A

lonestar tick; ambylomma americanum

80
Q

patho of red meat allergy

A
  • carb produced in the gut of a tick and found in red meat and some dairy –> Alpha-Gal
  • repeated exposure to the sugar induces an allergy to it and the person can no longer tolerate red meat
81
Q

sx of red meat allergy

A

urticaria to anaphylaxis

82
Q

evalulation for tick-borne dz after tick bite

A
  • size: the more engorged, the more likely bacteria passed through saliva
  • can’t pass bacteria if not attached
  • consider if endemic area
  • rash?
  • length of time attached

Infectious Disease (9 decks)

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