THE BLACK LEGGED TICK

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Lyme on the rise

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 Cycle3 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

They’re small

• 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

• A tick embeds its proboscis into the skin

• Releases saliva that anesthetizes the area and thins the blood

• Outward-flowing saliva alternates with inward-moving blood

• Infection enters to body system with the saliva

video and image generated by LifeHouse Productions

Infectious Ticks

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 life- and 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

SYMPTOMOLOGYLyme Disease

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 SymptomsEarly 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• Multiple rashes• Cardiac • Neurologic• Muscular

STAGE 3Long Term Lyme

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

COLLECTING TICKSHow we did it…

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.

COLLECTING TICKSHow we would like to do it better…

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– 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.

GISGlobal Information System

GIS Modeling: the Interrelationshipof 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.

BORRELIA BURGDORFERIWhat is

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

Chromosomal Gene Summary

DNA Molecule Summary • 18 DNA molecules• 28.5% G+C chromosomal bases• 63.1% linear DNA bases

• 853 genes― 793 protein coding genes― 502 genes assigned a role ― 51 genes not assigned a role― 102 hypothetical genes

Borrelia burgdorferi complete genome

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