Emerging and Endemic Vector-Borne Diseases in Michigan

Ned Walker

With thanks to:• Dr. Kim Signs, MDCH• Dr. Mary Grace Stobierski, MDCH• Dr. Gabe Hamer, MSU• Erik Foster, MDCH• Mike Kaufman, MSU• Betsy Brouhard, MSU• Bill Stanuszek, SCMAC• Randy Knepper, SCMAC

Purpose of this Presentation• Briefly discuss concepts of emerging,

vector-borne diseases• Tick-borne infectious diseases of

Michigan: emergence of Lyme disease• Mosquito-borne diseases relevant to

Michigan conditions

Concepts in Emerging Diseases

• New pathogens emerge and are discovered• Known pathogens expand geographic or host

range, increasing in incidence• Environmental receptivity: physical and living

landscape is receptive to invasion and establishment of pathogens whose range expands

• Most are zoonotic, many vector borne• Endemic diseases show cyclical activity,

suggesting occasional “re-emergence”• Importance of international travel, trade

If the St. Lawrence seaway is the front door, Michigan is the foyer for introductionof invasive species into North America.

Yemshanov et al. 2011. Trade associated pathways of alien forest insect entries in Canada. Biological Invasions 14:797–81

Human-assisted pathways of introduction of alien species into North America

Once introduced, is habitat suitable for establishment?(introduction > invasion/spread > establishment)

What is Lyme Disease? Tick‐borne disease transmitted by the Blacklegged tick, Ixodes scapularis

Bacterial, spirochete, Borelliaburgdorferi

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

Lyme disease ~~

Clinical Findings, 1992-2004

Lyme disease is a nationally notifiable disease. 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 in the United States:

1999 2009

....and over space

Current distribution of the blacklegged tick, Ixodes scapularis

Emergence and spread of Ixodes scapularis and Lyme disease in MichiganPrior 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.

Factors that influence tick habitat suitability include:Forest TypeSoil TypeHumidityHost Availability

Michigan Habitat Suitability

2004 2005 2006 2007 2008 2009

Northward spread of I. scapularisdetected continuously on coastal mice, but not on inland mice

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Northward spread of I. scapularisnymphs detected along coastal sites, but not inland

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Northward spread of I. scapularisdetected:  B. burgdorferi prevalence (%) in host‐seeking nymphs

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Phenology in Southern Michigan

Michigan Human Cases 2000-2010Lyme disease prevalence in Michigan, 2000 - 2010

Michigan regional trends, 2000-2010

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

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

Counties with human cases and identified as currently endemic, or “at risk” of vector tick populations

Counties with human cases and no direct evidence of vector tick populations

2010: Case Summary• 95 cases reported• Age range: 2 — 76 years• Median age: 37 years• Males: (57) 60% Females: (38) 40%• Onset dates of illness:

• March 10 — December 1• Exposure:

• In-State: 63• Travel Associated: 32• Unknown: 0

Distribution of Michigan-Acquired Human Lyme Disease Cases by

Reported County of Exposure- 2010

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Case Onsets for Michigan Exposures

2010 Lyme Disease Case Onset

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Conclusions and Considerations• Tick populations and Lyme disease risk continue to expand geographically

in Michigan, now encompassing the entire western shoreline of the Lower Peninsula, but at a relatively slow rate (decadal scale)

• The endemicity of Lyme disease in Michigan is increasing and the situation is worsening:– Tick surveys do not support widespread establishment of I. scapularis

across Michigan’s Lower Peninsula but show range expansion– The Lower Peninsula has large land area with suitable tick habitat,

based on a predictive and varified landscape model• Studies are on-going to estimate the entomologic risk index (density B.

burgdorferi infected nymphs/1000m2) at Sleeping Bear Dunes & National Lakeshore, and the Manitou Islands (data not shown)

• Several other tick surveys are on going and several citizens groups show strong interest in this disease system from various points of view

• Other tick borne disease agents are of real concern: Anaplasma, Babesia, Deer Tick virus, etc.

• Physician and veterinarian education and networking is key at this relatively early point in the process

Michigan Mosquitoes• About 60 species in the state, 250 in the US,

and 3,000 in the world• Only the females bite, and not all of our species

need blood, or bite people, or transmit pathogens

• The overwintering stage is species specific; eggs, larvae, or adult females may overwinter

• Mosquitoes are classified by their shape and anatomy

• An invasive species, Aedes japonicus:

Two major groupings:

Culicinae

Anophelinae

CulexAedes

Aedes

Anopheles

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New Jersey Light Traps - 2011

34 Yr. MEAN

Mosquitoes in Michigan, 2011: “It was a very good year … “

2011 was a wet year.More rain = more mosquitoes.

Mosquito-Borne Diseases• Malaria: once common in Michigan, now

eradicated but imported regularly• Bird malaria: common• Dog heartworm: common• Mosquito-borne viruses:

– Eastern Equine Encephalitis virus– La Crosse encephalitis virus– St. Louis encephalitis virus– West Nile virus– Dengue

Bird malaria is endemic to Michigan.

Study of house sparrows in 1986 showed 2.6% prevalence in Reed City. Other studies in N. America indicate higher prevalence (up to 40%) in rural areas. Passerine birds in general are thought to have an 11 - 67% infective rate for all types of malaria parasites.

Vignette:

Saginaw zoo penguin mortality -September 2004

Young (< 2 years old) black-footed penguin (Spheniscus demersus)

“Flock” suffering from aspergillosis(fungal lung disease)

Autopsy showed parasites in liver, spleen, brain, and lung tissue

Identified as Plasmodium spp. (probably relictum)

Treatments (Primaquine) given to other birds

All penguin collections in Michigan are put on malaria prophylaxis each summer by zoo vets to prevent deaths

“Sully” (RIP)

Dog Heartworm (affects cats also) Dirofilaria immitisVectored by many mosquito species. In Michigan, Aedesvexans and Ae trivittatus (summer floodwater species) are implicated along with Ae. canadensis (spring) and Anopheles species (summer, permanent water)

Coyotes, Foxes:Wild animal hosts

Cat infection: rare

Dog infection: common

Distribution of Dog Heartworm in the United States: Positive Dogs by Reporting Veterinary Clinic, 2010

Source: American Heartworm Association

Emerged from southern USnorthwards from the 1940s

Life Cycle of Human Malaria

Plasmodium vivax infection in a racing fan: local transmission of malaria, 1995

Anopheles mosquitoes collectedat the camp site.

MIS

But where did it come from?

Old pathogen,re-introduced.

Arboviruses in the United StatesSelected representatives by family

Eastern Equine Enceph. Cache Valley San Angelo Buttonwillow Reed Ranch

Venezuelan*Everglades

Lokern Jamestown Canyon Turlock Muir Springs

Western Equine Enceph. Northway Jerry Slough Potosi Malpais Spring

Highlands J Tensaw South River Rio Grande Hart Park/Flanders

Fort Morgan Main Drain Keystone Hughes Sawgrass

St. Louis Enceph. Virgin River Trivittatus Bluetongue Kern Canyon

Powassan Nepuyo Mahogany Hammock Enzootic Hemor. Dis.

West Nile Gumbo Limbo Shark River Mono Lake

Dengue* California Enceph. Pahayokee Colorado Tick Fever

Yellow Fever* La Crosse Mermet Vesicular Stomatitis

Togaviridae Flaviviridae

BunyaviridaeReoviridae

Virus Family: Rhabdoviridae

*not endemic

Arboviruses:

Arthropod – borne viruses

Not a taxonomic term andnothing to do with trees

Mosquito-borne viral diseases in people of Michigan, 2010, confirmed infections

• West Nile virus• Dengue• EEE• SLE• LaCrosse• Total

• 29• 9*• 3• 2• 2• 45

*Only notifiable since 2009

West Nile virus human cases, US, 2011, provisionalTotal: 690 including 43 deaths

Michigan: 33 including 2 deaths

Predicting WNV

• Are mosquito infection data any good?• What about weather?• What about mosquito/host contact rates?

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WNV does best in hot, dry years(2002, 2005). Warm, wet summersshow delays (2010). Cool, wetsummers show lower activity (2009).

West Nile virus activity in mosquitoes, metropolitan Chicago

Sequential sampling West Nile virus infected mosquitoes to predict humancases: A test case in metropolitan Chicago

It is possible to predict human cases at the local scale 2 weeks ahead of onsetby using mosquito infection curves, with sufficient sampling and testing.

Mosquito Bloodmeal Analysis: A horse at the Potter Park Zoo bitten by a WNV-positive mosquito

(This is mosquito CSI, folks)Sample #: Species: Fed On: Arboviral Results:65-071 Ae. triseratus Opossum Negative65-072 Unknown Gray Wolf Negative65-093 Ae. other Goat Negative65-135 Anopheles Goat Negative65-187 Ae. vexans Perching/Song Bird Negative

65-188 Ae. other Perching/Song Bird Negative

65-189 Culex sp. Gray Wolf Negative65-294 Ae. other Human Negative65-323 Culex sp. Horse WNV Positive65-391 Ae. other Perching/Song Bird Negative

65-510 Culex sp. Ostrich Negative65-557 Culex sp. House Sparrow Negative65-598 Ae. other Oryx Negative65-660 Ae. japonicus Antelope Negative

Special Concerns

• Economic downturn, loss of capacity, elimination of surveillance systems, loss of interest …

• Abandoned swimming pools• Retention and detention catchment

systems and NDPES, lack of attention to mosquito production issues

What we find out from passivesurveillance: let the cases cometo us

What we find out from activesurveillance: we go to the cases

Are we dropping our guard – apathy, priorities?Or is our guard dropping us – funding, politics?Does anybody care?

Abandoned swimming pools are a sign of the economictimes and are major mosquito factories

NPDES stormwater managementrequires retention/detention systemsnear developments and impervioussurfaces: creates mosquito habitat.

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Saginaw Co., Bridgeport township – 2006 human fatality

Saginaw Co., Birch run– 2009, 2011 mosquito positives

La Crosse encephalitis virus in Saginaw County

Dengue (DEN’ – gee): an emerging mosquito borne viral disease

Total: 10,040 human casesFlorida: 53Puerto Rico: 9,987

Dengue fever in Humans, USA, 2010A mosquito-borne virus in the same group as WNV

Imported dengue fever in Humans, USA, 2010

Total: 436 human casesFlorida: 125New York: 116Michigan: 9

“Cases of dengue in returning U.S. travelers have increased steadily during the past 20 years. Dengue is now the leading cause of acute febrile illness in U.S. travelers returning from the Caribbean, South America, and Asia. Many of these travelers are still viremic upon return to the United States and potentially capable of introducing dengue virus into a community with competent mosquito vectors. Because of concerns over the increasing number of travel-associated dengue infections, the risk for local transmission upon introduction of the virus, and the risk for potential transmission of the virus by blood transfusion, the Council of State and Territorial Epidemiologists (CSTE) made dengue a nationally notifiable disease in 2009.”

Morbidity and Mortality Weekly Report 2010;303(24):2465-2468.

“On April 9, 2010, a man aged 41 years from Key West was hospitalized with hematuria, leukopenia, and thrombocytopenia. His symptoms had begun April 5 with onset of myalgia, arthralgia, and fever, followed by development of a petechial rash and gingival bleeding on April 7. The patient previously had traveled to dengue-endemic regions but reported no travel outside the United States in 18 months.”

Historic Distribution of EEE United States

• Alphavirus• First

identified in 1930’s

• East coast, Gulf coast, Great Lakes

EEE Human Neuroinvasive disease, 1964-2008

58 / 58

Regional Glacial GeologyRegional Glacial GeologyLaurentide Ice Sheet just prior to its retreat from

Lower Michigan

(c. 17,800 C14 yrs ago)

Vegetation signatures: Tamarack, Black spruce, Red maple, Poison sumac, sphagnum,

MI EEE Cases, Equine and Human: 1980-2010

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Lesson: if we look, wewill find cases. Also 10La Crosse cases.

KENT

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LEELANAUANTRIM OTSEGO ALPENAMONTMORENCY

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Eastern Equine Encephalitis - Human1980 - 2010

1 human EEE case

2 human EEE cases

3 human EEE cases

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* *

* *

* Fatality

Total Cases: 17

Florida 4Massachusetts 1Michigan 3New York 1Rhode Island 1

Total = 10

Human EEE Cases, 2010

USGS Data

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# ReportsIll Horses

MMWR Wk 28: 7/11MMWR Wk 29: 7/19MMWR Wk 30: 7/26MMWR Wk 31: 8/1MMWR Wk 32: 8/8MMWR Wk 33: 8/15MMWR Wk 34: 8/22MMWR Wk 35: 8/29MMWR Wk 36: 9/5MMWR Wk 37: 9/12MMWR Wk 38: 9/19MMWR Wk 39: 9/26MMWR Wk 40: 10/3

Reports of ill EquineMichigan, 2010

Total Reports: 123 (9 lacked info)55 Tested Positive for EEE

July

August

Human cases

Horse cases are the only warning we have (but human cases co-occur)

Thank you for your attention!

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