Tick-borne Disease Flashcards
(82 cards)
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
2
Q
timing of tick disease transmission
A
-usu takes 24-48 hrs of attachment and feeding before transmission
3
Q
what % of tick bites result in tick-borne infection?
A
1%
4
Q
contents of tick saliva
A
- neurotoxins
- anticoagulants
- immunosuppressants
- anti-inflammatories
- pathogens: bacteria, viruses, nematodes
- toxins
5
Q
RFs for ticks
A
- male
- children
- farmers
- exposure to dogs
- live in wooded area
- exposure!!!
6
Q
RMSF classic presentation
A
- high fever
- HA
- petechial rash w/ hx of tick bite
7
Q
RMSF mortality rate
A
if untreated, 30% mortality rate
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
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
10
Q
S/Sx of RMSF
A
- sudden onset
- fever
- malaise
- severe frontal HA
- myalgia
- vomiting
(flu like so hard to diagnose)
11
Q
RMSF incubation period
A
2-14 days (avg. 7)
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
13
Q
Ddx of RMSF
A
- viral illness
- drug allergy
- measles
- meningococcemia
- mono
- roseola
- fifth dz
14
Q
lab detection of early RMSF
A
-nothing available for early RMSF –> dx based on clinical suspicion
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
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
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
18
Q
Tx timing for RMSF
A
- DON’T delay tx for lab results or rash
- treat immediately if true suspicion
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
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
21
Q
important ADRs of doxycycline
A
- esophagitis (take w/ full glass of water)
- teeth discoloration: don’t use in kids < 8 yo
- photosensitivity
22
Q
Complications of RMSF
A
- DIC
- skin necrosis
- cardiac arrythmias
- encephalitis
- GI bleed
- death w/o tx
23
Q
what is the MC tick borne dz in the US and Europe?
A
lyme dz
24
Q
bacteria in lyme dz
A
borrelia burgdorferi (spirochete)
25
tick vector for lyme dz
- deer tick (ixodes scapularis)
- most likely to transmit infection after feeding for 2 or more days
- reservoir is white tailed deer
26
tick vector for RMSF
- american dog tick (dermacentor variabilis) - in Eastern and South Central US
- rocky mt wood tick (dermacentor andersoni) - in mountain states west of the mississippi
27
pathophysiology of lyme dz
- borrelia in tick midgut --> salivary glands --> host
| - then spirochetes disseminate from the bite site
28
3 ways spirochetes disseminate from bite site in lyme
- cutaneous - travel centrifugally
- lymphatic
- hematogenous routes
29
S/sx of lyme dz
- many feel mildly ill
- myalgia
- arthralgias
- fatigue
- neck stiffness
- low grade fever
- regional adenopathy
30
halmark of lyme dz
erythema migrans
31
erythema migrans
- 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
32
early localized stage of lyme infection
- days to a month after infection
| - erythema migrans and viral-like sx
33
early disseminated stage of lyme infection
- weeks to months after infection
- neurologic sequalae (facial palsy, meningitis)
- cardiac dz (conduction deficits, blocks)
- severe malaise
34
late stage of lyme infection
- 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
summary of sx of lyme
skin, joints, nervous, cardiac sx
36
Ddx of lyme dz
- changing mole
- cellulitis
- tinea
- granuloma annulare
- fixed drug erruption
- contact dermatitis
- spider bite
37
dx of lyme dz
-erythma migrans + pt present in endemic area
OR
-serology + extracutaneous manifestations of lyme dz
38
Lab detection of lyme dz
- ELISA or IFA
| - if positive then western blot test for corroboration
39
tx of lyme dz
- doxycycline 100 mg BID
| - duration depends on stage of dz
40
alternative tx for lyme dz
- amoxicillin 500 mg TID x 14 days
| - cefuroxime 500 mg BID x 14 days
41
jarisch-herxheimer rxn
- 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
relapsing fever
- from bite of tick or louse infected w/ Borrelia
| - rare
43
common location for relapsing fever
-associated w/ sleeping in rustic cabins in mountainous areas of western US, canada, africa, europe
44
sx of relapsing fever
- HA, muscle and joint aches and nausea
| - recurrent, acute episodes of fever (up to 106) followed by periods of defeverscence of increasing duration
45
Dx of relapsing fever
-observation of Borrelia in blood smear, spinal fluid, or bone marrow of a symptomatic person
46
southern tick-associated rash illness (STARI)
- lyme like dz in southeaster and south central states
| - not fully characterized
47
STARI tick vector
- ambylomma americanum (lonestar tick)
- aggressively bites humans
- unknown cause
48
sx of STARI
- 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
lab eval and tx of STARI
- lab: negative lyme test; no commercially available test
| - tx: doxycycline 100 BID x 10 days
50
causative agent of ehrlichiosis
-ehrlichia chaffeensis: small gram negative bacteria that primarily invade leukocytes (monocytic)
AND
-anaplasma phagocytophilum (granulocytic)
51
ehrlichiosis tick vector
- lone star tick; amblyomma americanum (HME)
- blacklegged tick; ixodes scapularis (HGA)
- western blacklegged tick; ixodes pacificus
52
Hosts for ehrlichiosis
- coyotes
- mouse
- white-tailed deer
- horses (in OK)
53
pathophys of ehrlichiosis
bacteria infect either monocytes (HME) or granulocytes (HGA)
54
what is a characteristic of ehrlichiosis?
-morulae: bacteria divide w/i vacuoles inside leukocytes to form morulae
55
s/sx of ehrlichiosis
- hx of a tick bite
- most pts are asx
- incubation of 1-2 weeks
- rash is rare
- fever/HA
56
lab findings in ehrlichiosis
- leukopenia
- thrombocytopenia
- elevated LFT, LDH, and alkaline phosphatase
- indirect fluorescent antibody test is preferred diagnostic method
57
Ddx of ehrlichiosis
RMSF
58
complications of ehrlichiosis
- usually in immunocomrpomised
- renal failure
- disseminated intravascular coagulopathy
- meningoencephalitis
- adult respiratory distress syndrome
- seizures
- coma
59
tx of ehrlichiosis
- tx should not be delayed for labs
| - doxycycline 100 BID x 10 days or for 3-5 days after defervescence
60
mortality in ehrlichiosis
-HME: 2-5%
-HGA: 7-10%
(probably overestimations)
61
tularemia (aka rabbit fever) bacteria
- francisella tularensis
| - gram negative bacteria
62
tularemia tick vectors
- american dog dick: dermacentor variabilis
| - lone star tick; amblyomma americanum
63
hosts for tularemia
rodents and rabits
64
epidemiology of tularemia
avg. 25 cases/yr in OK
65
how to become infected w/ tularemia
-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
clinical presentation of tularemia
- 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
ulceroglandular type of tularemia
- 80%
- bacteria enters through scratch, tick bite, or abrasions
- fever, ulcer, lymphadenopathy
68
glandular type of tularemia
- similar to ulceroglandular but no skin lesion
| - organism is presumed to enter via inapparent abrasion and then spreads
69
oculoglandular type of tularemia
- 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
oropharyngeal type tularemia
- 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
pneumonic type tularemia
- from either inhalation or hematogenous spread
- MC in lab workers
- dry cough, dyspnea, and pleuritic chest pain
- can get pneumonia and/or ARDS
72
typhoidal type tularemia
- 10-15%
- more severe
- likely from bacteremia
- fever, chilles, myalgias, malaise, weight loss
- often present w/ pneumonia
73
dx of tularemia
- culture of organism from blood, sputum, wound (have to culture in cysteine)
- serology: 1:160 or higher titer is positive
74
tx of tularemia
-streptomycin 10mg/kg BID (IM) x 7-10 days
75
prognosis of tularemia
- mortality in untreated: 5-15%
| - mortality in treated: < 4%
76
bioweapon potential of tularemia
- 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
tick paralysis
- 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
ticks implicated for tick paralysis
- dermacentor
- ixodes
- amblyomma
- usually attached 4-7 days before paralysis occurs
79
red meat allergy tick vector
lonestar tick; ambylomma americanum
80
patho of red meat allergy
- 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
sx of red meat allergy
urticaria to anaphylaxis
82
evalulation for tick-borne dz after tick bite
- 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
