Lyme on the rise
THE BLACK LEGGED TICK
HTTP://WWW.LIFEHOUSEPRODUCTIONS.COM/TICK_ANIM.HTML
The Increase of Lyme in Minnesota
• A local family physician inquires about Lyme disease
noting an increase of patients experiencing:
– ring shaped rashes
– headaches
– fever chills
• Rigid diagnosis was not made as confirmation requires
time that a patient may not have.
High Risk Areas for
Tick-borne Diseases in Minnesota
• The physician expressed
concern that the map by
Minnesota Department of
Natural Resources may be
inaccurate.
• People in the Duluth area
could be better informed
before planning outdoor
activities.
Outline
• Ticks
– Life cycle of ticks, life cycle of disease
• Lyme Disease
– symptoms
• Collecting Ticks
• GIS
• Borrelia Burgdorferi
– The bacteria responsible for Lyme
• Vaccines
• Discussion
Deer Tick Habitat
• High concentration in
northeast region of U.S.
• Wooded areas, forests,
over-grown grassy areas
and trails
• Prefer moist and humid
environments
• Sit on tips of grass and
quest for a host
Black legged tick, Ixodes scapularis,
questing on a stick.
Deer Tick Life Cycle
3 stages of life, 1 feeding each stage
• Year 1 – Spring, Summer
– Eggs hatch into larvae
– Feed once and molt into nymphs
– Nymphs become dormant
• Year 2, May – July
– Nymphs feed
– At this time, the nymph may
transmit disease (shown in grey)
• Year 2, Oct - Nov
– Adults feed primarily in Fall.
– Eat, spit eggs and die
American Lyme Disease Foundation
Graphic courtesy of Green Pest Control MN
Infested Ticks
• Nymphal ticks are the worst for infection
– Hard to detect
– Their bites cause much milder pain than
adult ticks’
• Ticks carry Borrelia burgdorferi
(Bb) in their gut
– The bacteria responsible for
Lyme Disease
They’re small
Infectious Ticks
• A tick embeds its
proboscis into the skin
• Releases saliva that
anesthetizes the area and
thins the blood
• Outward-flowing saliva
alternates with inwardmoving blood
• Infection enters to body
system with the saliva
video and image generated by LifeHouse Productions
Transfer of B. burgdorferi to Ticks
• Bb occurs in nature and is
picked up by rodents and
other small mammals.
• Deer ticks take blood meal
from these small mammals during the larval stage of lifeand contract bacterium.
Transfer of B. burgdorferi to Humans
• Bb attaches to the gut
― Outer surface protein A
(OspA)
• Bb stays in the gut until the
next meal
― Blood meal
―  Osp A,  Osp C
• Bb goes to salivary glands
where it can enter the host
Lyme Disease
SYMPTOMOLOGY
Contracting Lyme Disease
• The bite of an infested nymph or adult tick can transmit
Lyme after it attaches to the host for 36 – 48 hrs
– generation time of bacteria B. burgdorferi: ~ 12 hrs
– It takes several hours before a large enough infectious
dose of Bb can infiltrate the new host.
Nature Reviews / Microbiology
Symptomology of Lyme Disease
• Lyme is a multisystem inflammatory disease
– affects the skin in the early stage
– then spreads to the joints, nervous system and may
eventually affect organ systems.
• Symptoms are divided into 3 stages
– each stage more advanced than the previous.
Stage 1 Symptoms
Early localized infection
• Skin Rash Around Tick Bite
– 40 -75% present with
rash
• Mild Illness
• Flu-like Symptoms
• Fevers
• Chills
• Swollen Lymph Nodes
• Headache
• Stiff Neck
• Muscle Fatigue
• These symptoms may
appear up to a month
after infection.
Stage 2 Symptoms
• Within weeks of stage one symptoms, the bacterium may
spread to other parts of the body through the bloodstream
Early Disseminated Infection
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•
•
•
Multiple rashes
Cardiac
Neurologic
Muscular
Long Term Lyme
STAGE 3
Late-Stage Symptoms
• This is the most serious stage of the disease, when
treatment was either not successful or never started
• May occur months to years after initial infection.
• Symptoms at this stage are primarily rheumatologic
and neurologic, and mostly untreatable.
Stage 3
• Also known as:
– Post-Lyme Disease Syndrome
– Chronic Lyme Disease
• Diagnosis
– Difficult to diagnose
– If symptoms persist for 6 months after treatment
Stage 3
• A systemic debilitating condition
• Persistent
– Months to Years
– Damage to joints, nerves, brain
Symptoms
• Rheumatoid Arthritis
• Atrioventricular conduction abnormalities
– (AV heart block) ~ irregular heartbeat
• Encephalopathy ~ disease on the brain
• Decreased memory
• Sleep Disturbances
• Mood changes
• Ataxia ~ nervous system
• Depression
• Anxiety
Disease Process
• Bacteria penetrates blood vessels
• Bacteria exits vessels in various organs and tissues
• Body may fight off infection
• Host immune system may attack healthy tissue
– Probable cause of long term complications
• There are clues to the mechanisms of Post-Lyme Disease
but it is not fully understood
Diagnosis
•
•
•
•
Clinical Evidence
Enzyme Linked Immunosorbent Assay (ELISA)
Western Blotting
Indirect Immunofluorescence
– Detect antibodies
– Lacks sensitivity and specificity
• PCR
Diagnosis of Early Lymes. Journal of Clinical Microbiology.
http://jcm.asm.org/cgi/reprint/30/12/3082
Treatment
• Short Term Treatment
– Antibiotics can shorten EM and prevent arthritis
• Penicillin
• Amoxicillin
• Tetracycline
– Can still have symptoms of Chronic Lyme
• Chronic Lyme
– Risks are high and benefits are low to antibiotics
– Immunosuppressive drugs
The Clinical Spectrum and Treatment of Lyme Disease. The Yale Journal of Biology and Medicine
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2590003/?tool=pmcentrez
How we did it…
COLLECTING TICKS
Our Tick Collection Methods
Materials:
• Light-colored bed sheet
• Hand held GPS devices
• Sealable plastic containers
Methods:
•We stopped at the banks of
pre-selected locations listed
on a GPS.
•We separated into groups of
two, held sheets open, and
swept the ground.
•After 100 yards we
examined the sheet in hopes
of finding black-legged ticks.
Our Results
• We collected over two days, a total of eight stops.
• We found 6 ticks.
• All of the ticks found were in their nymph stage and
were not much larger than the point of a pencil.
• Our sampling was done during the mid summer
season rather than the late spring or fall
– this may be why so few deer ticks were collected.
• Some observations were made about the general
environment in which the ticks were found.
How we would like to do it better…
COLLECTING TICKS
Tick Collection Methods
• What criteria, procedures, and equipment should be
used when collecting ticks in the wild?
Where are ticks generally located
in the Midwest?
• Near or in deciduous forests
• Dry to mesic (moderate moisture) forests
• Alfisol-type soils of sandy or loam-sand textures
overlying sedimentary rock
• Along ecotones -boundaries between varying
ecosystems
Constructing Dragging Equipment
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–
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70 x 90cm piece of light-colored corduroy
1cm diameter wooden dowel along leading edge
Steel rod sewn into trailing edge for added weight
Rope or wood handle to allow front edge of sheet to contact
vegetation
VS.
Collection Techniques from
Schulze/Jordan:
• The same individual should perform the dragging
– Consistency -speed, height
• Collect hourly from dawn ‘til dusk
• 100m long transects (sections)
– collect every 10m to prevent ticks from falling off
• Randomize dragging order, direction of travel, location
within each transect (left, right, center) to minimize
repeated dragging of same areas
• Minimize dew collection by drying sheets in between
collections
Statistics
• For each sampling event use a ‘Weather Station’:
– Place Weather Station in center of area,
1m above vegetation height
– Ambient Temperature
– Ambient Humidity
– Litter temperature and humidity (digital thermometer)
• At least 2.5cm below leaf litter surface but not into soil
Sampling Data Sheet:
Works Cited for Collection Techniques:
• Shulze, Terry, Jordan, Robert. “Meteorologically Mediated
Diurnal Questing of Ixodes scapularis and Amblyomma
Americanum Nymphs.” Journal of Medical Entomology. 2003.
• Lindstrom, Anders, Jaenson, Thomas. “Distribution of the
Common Tick, Ixodesricinus, in different vegetation types in
Southern Sweden.” Journal of Medical Entomology. 2003.
Global Information System
GIS
GIS Modeling: the Interrelationship
of Ticks, Mice, and their Environment
Use an appropriate collection device
Sample small specific areas
Test ticks for Borrelia burgdorferi
Look for evidence of a pattern in the incidence of
infected ticks
• If specific reservoirs of bacteria are found, a map could
be made based on likelihood of the existence of the
bacteria.
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What is
BORRELIA BURGDORFERI
Characteristics
• Named after American scientist Willy Burgdorfer who
in 1982 isolated and determined the bacterium.
• Lyme Disease is the most common tick-borne disease
in the US.
• Borrelia burgdorferi are
– spiral shaped microorganism (spirochetes)
– Gram-negative
– Motile
Borrelia burgdorferi
complete genome
Chromosomal Gene Summary
• 853 genes
― 793 protein coding genes
― 502 genes assigned a role
― 51 genes not assigned a role
― 102 hypothetical genes
DNA Molecule Summary
• 18 DNA molecules
• 28.5% G+C chromosomal bases
• 63.1% linear DNA bases
Characteristics
• Chemo-organotropic
– derive energy by metabolizing organic molecules.
• They cannot synthesize their own amino acids, fatty
acids, enzyme cofactors, and nucleotides.
• Microaerophilic
– Too much or lack of oxygen can be harmful to them.
• Catalase negative
– they are unable to break down hydrogen peroxide.
• Optimal growth temperature is 34° to 37°C.
Surface proteins on Borrelia burgdorferi
• OspA
– expressed while Bb is in the tick’s midgut
• OspC
– expressed during tick’s blood meal
– allows Bb to relocate to salivary glands
(36-48 hr)
OspC binds to
Salp15 in the tick
salivary gland
Salp15
• Facilitates transmission of
Bb from tick to host
• Allows Bb to evade host
immune system
• Has immunosuppressive
activity in the host
Immunosuppressive activity of Salp15 within host
Salp15 binds to CD4+ of
T-cells inhibiting:
• the normal production and
secretion of interleukin-2
• TCR-triggered calcium signals
• activation of transcription
factors
VACCINES
Current Vaccines
• Currently, there is no human vaccine on the market.
• One did exist called LYMErix but is no longer available.
– Originally approved by the FDA in 1998
to help prevent the disease, the vaccine
was pulled from the market by the
manufacturer in 2002 due to poor sales
and concern that the vaccine could
trigger arthritis problems though the
FDA never found conclusive evidence
that the vaccine was dangerous.
(WebMD)
Possibilities for a Future Vaccine
• Salp 15 is the protein that enables the bacteria to enter
the host initially undetected.
• If there is some way to produce
a vaccine with Salp15, this could
allow the host’s body to
recognize and fight off the
bacteria faster and more
efficiently.
• If there are other ways to
degrade the protein in the host’s
body the bacteria would become
vulnerable to an immune
response.
Problem Based Learning
MIKE,
CHRISTINA,
Discussion
• Prevention
• Life cycle interruption
– Habitat
– Surface protein
• Human immunity
– Salp 15
– glycoprotein