Foster CD Conference 2012 - Michigan · NPS and MDNR from visitors and staff at SBDNL Photo: Graham Hickling Kellogg Hotel and Conference Center May 16, 2012 - East Lansing, MI Motivation

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Erik FosterMedical EntomologistMichigan Department of Community Health

Kellogg Hotel and Conference CenterMay 16, 2012 - East Lansing, MI


Outline

America’s Most Beautiful PlaceMotivation for study Lyme disease Epidemiology

in Michigan A note on human case

investigation Study results

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Well Deserved Recognition


SBDNL Park Statistics

Est. 1970

Annual Visits ‐ 1,143,857

Employees ‐ 46 permanent, 84 seasonal

Volunteer Hours ‐ 29,595 from 850 volunteers

Area ‐ 71,199 acres

Lake Michigan Shoreline ‐ 65 miles (35 miles on the mainland)

Campgrounds ‐ 9 (357 sites)

Miles of trails ‐ 105

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Unwanted Visitors

MDCH and MSU have been conducting collaborative surveillance for blacklegged ticks and Lyme disease since the 1980’s

In the Lower Peninsula the Lake Michigan shoreline has the highest blacklegged tick populations, but historic tick surveys have so‐far shown little risk at southern sites at SBDNL

Since 2010 reports of blacklegged tick encounters have increased to NPS and MDNR from visitors and staff at SBDNL Photo: Graham Hickling


Motivation for Study

Reported Lyme disease cases in Michigan (2010‐2011) have been linked to potential exposure at SBDNL and specifically North Manitou Island

SBDNL accommodates ~1.2 million visitors per year during the peak of tick season

Michigan DCH, MSU, and NPS discussed need/plan to evaluate risk on Manitou Islands and SBD mainland

Documenting the presence and distribution of blacklegged ticks in the park will assist the NPS in worker protections and directing public education re: tick‐borne disease prevention

Photo: Jen Sidge

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Project Approach: What and Where to Sample?

Objectives1. Determine if Ixodes scapularis is

present, and at what concentration at North and/or South Manitou Islands

2. Determine if B. burgdorferi is present in ticks and/or wildlife at four sites within the SBDNL

3. Compare findings with a positive control site within a Lyme disease endemic region of Michigan’s Lower Peninsula

4. Provide recommendations to the NPS related to potential Lyme disease risk based upon survey results at SBDNL

Four experimental sitesMainland SBDNL: Southern and Northern siteManitou Islands: South and North islands

Control siteVan Buren State Park Photos: Jean Tsao


SBDNL Sites

Dragging: along trails and transects: ~ 3000 m dragging per site/visit (June‐October, 2011)

Rodent trapping: Two nights with 150 – 216 traps per night

(June‐September, 2011)

Hunter killed deer: Annual deer hunt October 29 –November 5, 2011

North Manitou Island

South Manitou Island

DH Day Campground

Platte River Campground

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SouthSouth NorthNorth

Motorized vehicles allowed

Organized campgrounds

Village Area/Lighthouse

Daytrips Common

Higher visitation

No motorized vehicles

“Wilderness” camping

No daytrips

Lower visitation

Potentially higher exposure to wooded environments

Island Comparison – What we know going in

WHAT IS LYME DISEASE?

HOW PREVALENT IS IT IN THE U.S. AND MICHIGAN?

WHAT ARE THE RISK AREAS?

First Off…..

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Tick-Borne Illness in Michigan


What is Lyme Disease?

Tick‐borne disease transmitted by the Blacklegged tick, Ixodes scapularis

Bacterial, spirochete, Borellia burgdorferi

Transmission from tick to host takes 24‐48 hours

No person‐to‐person spread

Range of potential symptoms and difficulties interpreting laboratory results makes reported Lyme difficult to characterize for public health surveillance purposes

phil.cdc.gov

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Clinical Findings, 1992-2004

Lyme disease is a nationally notifiabledisease. The Centers for Disease Control and Prevention collect and analyze data from all states.

The graph at right illustrates percent of clinical findings among 119, 965 patients for whom at least one symptom was reported.


Lyme disease has emerged over time....

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1999 2009

....and over space


Current tick distribution

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How can it be that our most beautiful place is plagued by ticks?Prior to 2002, No local

populations of blacklegged ticks had been identified in the Lower Peninsula.

Over the past decade, extensive field surveys have documented a northward progression of tick invasion along Michigan’s western shoreline.


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Tick Phenology in Southern Michigan

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total female male nymph

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Infection Analysis by Stage at a Southern MI Study Site: 2002‐2004

Total No. Tested Number Infected Infection Rate

40%

34%

15%

Historic Southern Michigan Infection Rates


Michigan Human Cases 2006-2011

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Case Onsets: 2011

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May June July August


Michigan regional trends: 2000-2011

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2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

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Linear (SW MI Exposure) Linear (UP MI Exposure)

Linear (Other MI Exposure) Linear (Out of State Exposure)Out of State ExposureUpper Peninsula Exposure

Other Michigan ExposureWestern Lower MI Exposure

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(Left) Lyme disease risk based on known populations of infected tick vectors. (Right) Incidence of locally acquired human Lyme disease cases, 2011.

EPI SNAPSHOT 2011

Incidence of locally acquired Lyme disease

Full State:

1.06 cases/100,000 pop.

Western Upper Peninsula:

17.49 cases/100,000 pop.

[*99.98 cases/100,000 pop. In Menominee Co.]

Western Lower Peninsula:

1.26 cases/100,000 pop.

Counties outside of western UP/LP regions:

0.09 cases/100,000 pop.

Lyme disease risk and human case incidence in Michigan, 2011

BROAD SUMMARY

INTERESTING DIFFERENCES

TANTALIZING SCIENCE

Interesting Findings at Sleeping Bear…..

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Preliminary Summary

Ixodes scapularis ticks were found at all SBD sites surveyed

Borrelia burgdorferi was isolated from ticks or animals at all sites EXCEPT South Manitou Island

Mainland site tick densities and infection rates are indicative of initial invasion/ongoing colonization

High adult questing density on NMI during October hunt

Adult tick density and infection rate at North Manitou Island is comparable to an established, southern Michigan control site

Tick Contact in the Environment

Ticks sampled by dragging a 1‐meter x 1‐meter corduroy cloth through forest understory

When compared with control site, NMI has highest adult and nymph stage tick density; densities as S. Platte have increased. Little activity at DH Day and SMI.

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Nymph StageTicks

Results of >44,000-m2 drag-sampling (>27 miles)

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“Entomological Risk Index”

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Early‐Mid June Mid‐July Mid‐September Mid‐Late

October

# In

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ticks/1000m2

Adult Tick Entomological Risk Index

VBSP NMI SMI DHD SP

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Nymphal Tick Entomological Risk Index

VBSP NMI SMI DHD SP

“The amount of chipmunks and breeding habitat for the nymphs (young ticks) is a perfect cocktail for the spread of Lyme disease at a alarming rate....”

Eastern chipmunks are highly competent hosts for B. burgdorferi and previous studies point to high parasitism by nymphalblacklegged ticks.

North and South Manitou Islands have high populations of this important host species compared to a southern Michigan control site. 0

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Early‐Mid June Mid‐July Mid‐September

Unique Captures

Eastern Chipmunk Captures ‐ SBDNL Tick Survey Data 2011

VBSP (Control) NMI SMI DH Day S. Platte

Photo: Jean Tsao

Results of >3,400 trap nights

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Proportion W

FMO w I.scap NN

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Ticks on wildlife hosts

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Proportion EACH w

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VB (Control)

NMI

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SBD

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Proportion EACH w

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B. Burgdorferi infected animals

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Proportion of tissue biopsies positive

VB (Control)

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SMI

DHD

SBD

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Hunter Collected Ticks

In October, 2011 hunters bound for the NMI annual hunt were recruited to collect ticks from themselves and harvested deer.

Hunters were asked to participate in survey and briefed about ticks and Lyme disease risk while en‐route to the island

40 collection kits were distributed including forceps, collection tube, instructions, data sheet, pen and gloves

Hunters were given gift card to participate

Photo: Jen Sidge


Hunter collected ticks results

40 collection kits distributed 22 (55%) kits returned at the end of the hunt

196 ticks collected (all adult I. scapularis)

Collection range was: 1 to 24 ticks with a mean of 9.38 ticks/hunter

Probable tick collection locations were marked on a map by hunters

48% of ticks collected showed evidence of B. burgdorferi infection by PCR

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North ManitouNorth Manitou South ManitouSouth Manitou

High density small mammal hosts

Mixed deciduous, sandy soils

White‐tailed deer population

Other medium sized mammals (coyote)

HIGH density ticksHIGH B. burgdorferi rate

High density small mammal hosts

Mixed deciduous, sandy soils

NO White‐tailed deer population

Few to no other medium sized mammals

LOW density ticksNO B. burgdorferi

Compare North vs. South Island

How did I. scapularis ticks arrive on the islands?


Conclusions

Lyme disease is the most commonly reported vector‐borne disease in Michigan

Tick populations and Lyme disease risk continue to expand geographically in Michigan, now encompassing the entire western shoreline of the Lower Peninsula

More study is warranted to estimate the entomolgic risk index (density B. burgdorferi infected nymphs/1000m2) at SBDNL as well as: What factors contribute to differences in tick density and infection rate

(NMI vs. SMI)?

Do birds play a role in introducing ticks to the islands?

Are the tick introduction rates similar between the islands?

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Michigan Classification Flowchartfound at www.michigan.gov/cdinfo

Documents

Foster CD Conference 2012 - Michigan · NPS and MDNR from visitors and staff at SBDNL Photo: Graham Hickling Kellogg Hotel and Conference Center May 16, 2012 - East Lansing, MI Motivation