emerging and endemic vector- borne diseases in michigan · 2017. 9. 13. · factors that influence...
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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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Prop
ortio
n infested
Northward spread of I. scapularisnymphs detected along coastal sites, but not inland
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2004 2005 2006 2007 2008 2009
Average de
nsity
nym
phal
I. scap
ularis
per 1
000 m
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Northward spread of I. scapularisdetected: B. burgdorferi prevalence (%) in host‐seeking nymphs
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50
2004 2005 2006 2007 2008 2009
Average de
nsity
nym
phal
I. scap
ularis
per 1
000 m
2
12.5
8.2
12.5
19.2
4.9
19.0
07.1
5.0
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1 2 3 4 5 6 7 8 9 10 11 12Month
Relativ
e activ
ity
Larvae Nymphs Adults
Phenology in Southern Michigan
Michigan Human Cases 2000-2010Lyme disease prevalence in Michigan, 2000 - 2010
Michigan regional trends, 2000-2010
05
1015202530354045
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
No.
Cas
es
Year
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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1
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1
1
Case Onsets for Michigan Exposures
2010 Lyme Disease Case Onset
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MMWR Week
No. C
ases
All Cases w/Reported OnsetMI UP ExposuresMI West Exposures
Jun SeptAugJulMay
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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25
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75
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125
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175
2005/
16
5/23
5/30 6/6
6/13
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6/27 7/4
7/11
7/18
7/25 8/1
8/8
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Mos
quito
es/tr
ap/n
ight
Sampling Period (May 16-Sept. 16)
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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Cul
ex in
fect
ion
rate
Week number
Culex spp. mosquito infection rate (2005-2010)
200520062007200820092010
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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Dry Retention
Wet Retention
Mitigated wetland
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Dry Retention
Wet Retention
Mitigated wetland
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Dry Retention
Wet Retention
Mitigated Wetland
Culex pipiens
Culex territans
Anopheles spp.Mos
quito
es p
er s
tand
ard
dip
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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Equi
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ases
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Hum
an Cases
Equine CasesHuman Cases
2002 WNV Outbreak
Lesson: if we look, wewill find cases. Also 10La Crosse cases.
KENT
HU RON
BAY
SANILAC
LAKE
IONIA
OAKLAND
WAYNE
IOSCO
ALLEGAN
SAGINAW
EATON
TUSCOLANEWAYGO
CLA RE
CASS
BARRY
LAPEER
ALCONA
ST. CLAIR
JACKSONCALHOUN
IN GHAM
OTTAWA
MASON
GENESEE
OSCODA
CLINTON
GRATIOT
LENAWEE
OCEAN A
MONTCALM
OGEMAW
MECOSTA
OSCEOLA
ISABELLA
MONROE
MIDLAND
WEXFORD
BRANCH
WASHTENAW
GLAD WIN
MANISTEE
VAN BUREN
MACOMB
KALKASKA
BERRIEN
MISSAUKEE
LIVINGSTON
C RAWFORDBENZIE
MUSKEGON
KALAM AZOO
ARENAC
HILLSDALE
ROSCOMMON
SHIAWASSEE
ST. JOSEPH
GRAND TRAVERSE
LEELANAUANTRIM OTSEGO ALPENAMONTMORENCY
±
0 10 20 305Miles
Eastern Equine Encephalitis - Human1980 - 2010
1 human EEE case
2 human EEE cases
3 human EEE cases
*
* *
* *
* Fatality
Total Cases: 17
Florida 4Massachusetts 1Michigan 3New York 1Rhode Island 1
Total = 10
Human EEE Cases, 2010
USGS Data
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27 29 31 33 35 37 39MMWR Week
# 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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