Tick Talk: Advancing the Understanding and Prevention of Tick … · 2019-11-21 · Advancing the...
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Tick Talk: Advancing the Understanding and Prevention
of Tick-borne Diseases
Seemay ChouUCSF Dept of Biochemistry & Biophysics
Osher Mini Med School, 11/14/19
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Malaria Sleeping sickness Lyme disease
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Topics:1. Ticks and their vector capacity
2. Challenges associated with diagnosing Lyme
3. Strategies for blocking tick-borne diseases
4. What else can we learn from ticks?
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Ixodes scapularisIxodes pacificus
Dermacentor andersoniDermacentor variablis
Amblyomma maculatumAmblyomma americanum
EhrlichiosisRickettsiosis
Mammalian Meat Allergy
Lyme DiseaseAnaplasmosis
BabesiosisPowassan Disease
Rocky Mountain Spotted FeverColorado Tick Fever
Ticks are vectors for human diseases
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Different ticks have different lifestyles
Hard
Ixodes scapularis
scutumcapitulum
Soft
Ornithodoros savignyi
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Different ticks have different lifestyles
Hard
Ixodes scapularis
• 3 stages: larvae, nymphs, adults• Single bloodmeal between each• Bloodmeal: days to over a week
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Borrelia burgdorferi Lyme diseaseIxodes scapularis
Centers for Disease Control
Cases have tripled in past decade
Most commonly reported vector-borne disease in U.S.
Lyme disease cases in the U.S. are on the rise
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Tick–pathogen relationships are remarkably specific
Source: CDC.gov
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Lyme disease is restricted to where tick vectors are
Source: CDC.gov
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West coast vector: Ixodes pacificus
Western blacklegged tick
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West coast vector: Ixodes pacificus
Sceloporus occidentalisWestern fence lizard
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County level distribution of submitted Ixodes
Nieto et al, 2018
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Distribution of other tick species received
Nieto et al, 2018
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All submissions(4261)
Ixodes scapularis(2574, 60%)
Questing/biting ticks collected from humans in NE
Dermacentor variablis 33%; Amblyomma americanum 2%Porter et al, 2019
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Submissions varied by species, stage, seasonN
umb
er o
f tic
ks re
ceiv
ed/w
eek
Porter et al, 2019
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0
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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar
Ixodes species also had different collection patterns
Ixodes scapularisIxodes pacificus
Courtesy of Wendy Adams, Nate Nieto
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Vector capacity = ecology + competence
Vector competenceIntrinsic ability to acquire, carry, and transmit microbes.
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B. burgdorferi transmission cycle
Reviewed in Sonenshine, D. Biology of Ticks, 2014 ed.
Adults
Nymphs
Larvae
Acquisition
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Topics:1. Ticks and their vector capacity
2. Challenges associated with diagnosing Lyme
3. Strategies for blocking tick-borne diseases
4. What else can we learn from ticks?
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Borrelia burgdorferi
Lyme disease is difficult to diagnose/treat
Arthritis, fatigue, neurodegeneration
Incubation period: 3-32 days
Limited window for treatment
Difficult to detect in blood
Unsuccessful vaccine (2002)
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Ticks can carry multiple pathogens
Nationwide
Borrelia burgdorferi sl 6.14%Borrelia miyamotoi 0.91%
A. phagocytophilum 1.76%
Babesia microti 0.66%
*Ehrlichia and Rickettsia spp., high prevalence in some places (~40%)
CoinfectionsBb + Bm (N = 11)Bb + Ap (N = 14)Bb + Bab (N = 8)
Bm + Ap (N = 1)Bm + Bab (N = 2)
Ap + Bab (N = 1)
Tri-infectionBb + Bm + Bab (N = 3)
New York and PennsylvaniaBb + Ap + Bab (N = 1)
Minnesota
Courtesy of Wendy Adams, Nate Nieto
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Topics:1. Ticks and their vector capacity
2. Challenges associated with diagnosing Lyme
3. Strategies for blocking tick-borne diseases
4. What else can we learn from ticks?
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Nature Medicine, 2014
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Paratransgenesis to control vectors
A. aegypti mosquitoes transmit Zika virus(also dengue, chikungunya, yellow fever)
Infect with bacterium Wolbachia
Aedes aegypti
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The Lyme pathogen is in gut of I. scapularis ticks
mg = midgut
ov = ovary
Ross B et al, ISME (2018)
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Some ticks have other kinds of bacteria
Negatively correlates with B. burgdorferi
Ross B et al, ISME (2018)
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Topics:1. Ticks and their vector capacity
2. Challenges associated with diagnosing Lyme
3. Strategies for blocking tick-borne diseases
4. What else can we learn from ticks?
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Ticks are master regulators of us (their food)
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Both ticks and pathogens rely on saliva
Pool feeders
Prolonged bloodmeals
90% of fluid is secreted
Saliva-activated transmission
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Adventures in collecting tick spit
~102 proteins in sialomeComposition changes over timeArthropod saliva is protease-rich
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Questions?