Climate Change and Vector-borne Disease Risk in Minnesota. Dave Neitzel, MS Minnesota Department of Health March, 2010

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1 Vectorborne Disease

2 Climate Change and Vector-borne Disease Risk in Minnesota Dave Neitzel, MS Minnesota Department of Health March, 2010

3 Objectives 1. Outline the primary tick and mosquitotransmitted disease concerns in Minnesota 2. Describe how climate change may change the risk of these diseases within the state

4 Vector-borne Disease Terms Disease name of human illness Disease agent Vector Host Reservoir name of agent causing disease tick or mosquito that transmit disease agents animal or human fed on by vector animal where vector obtains disease agent while feeding

5 Vector-borne Disease Transmission to Humans Dependent on a large number of factors; most relate directly or indirectly to: disease agent arthropod vector human host Climate change may affect all of these factors

6 Tick-borne Diseases of Concern in Minnesota Endemic Rare or Emerging - Lyme disease - Human anaplasmosis - Babesiosis - Rocky Mountain spotted fever - Human ehrlichiosis - Powassan encephalitis

7 Minnesota s Primary Vector Tick Ixodes scapularis (blacklegged tick or deer tick) Ixodes spp. Vector distribution, United States CDC/ Michael L. Levin, Ph. D. (Public Health Image Library)

8 Blacklegged Tick Life Stages Nymph Adult (female) Larva

9 Blacklegged Tick Nymph

10 Blacklegged Tick Habitat

11 Main Reservoir Host: White-Footed Mouse (Peromyscus leucopus)

12 Main Reproductive Host: White-Tailed Deer (Odocoileus virginianus) CDC: Public Health Image Library

13 Transmission of Disease Agents from Blacklegged Ticks to Humans Must be nymph or an adult female Must be carrying the pathogen already (not all ticks are infected) Must be attached for a long time hours (human anaplasmosis) hours (Lyme disease)

14 Number of Reported Cases Reported Tick-borne Disease Cases, Minnesota, (n = 11,441) 1200 Lyme disease Human anaplasmosis Babesiosis Year

15 Percent of Cases Reported Tick-borne Disease Cases by Onset Month, Minnesota, (n=7,897*) 50% 40% Lyme disease Human anaplasmosis Babesiosis 30% 20% 10% 0% Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month of Onset * Excluding Lyme disease cases without EM and cases with unknown onset

Average Annual Incidence* of Lyme Disease by County of Residence, United States, 1992-2006

16 Average Annual Incidence* of Lyme Disease by County of Residence, United States, (n = 248,074) * Reported cases/100,000 population CDC, MMWR Surveillance Summary, Oct. 2008

17 MDH Documentation of Changing Tick-borne Disease Risk Interviews of case-patients to determine tick exposure locations Field studies to document: expanding tick distribution tick infection prevalence with various disease agents

18 High Risk Areas for Kittson Marshall Polk Roseau Pennington Beltrami Lake of the Woods Koochiching St. Louis Tick-borne Diseases in Minnesota Cook Red Lake Clear Water Lake Itasca Norman Mahnomen Hubbard Cass Clay Becker Aitkin Wadena Crow Wing Carlton Wilkin Ottertail Pine Todd Mille Lacs Kanabec Grant Douglas Morrison Benton Traverse Stevens Pope Stearns Isanti Big Stone Sherburne Chisago Swift Kandiyohi Anoka Meeker Wright Wash - ing- Chippewa Ramton Hennepin sey Lac Qui Parle McLeod Renville Carver Yellow Medicine Scott Dakota Sibley Lincoln Lyon Redwood Le Nicollet Sueur Rice Goodhue Wabasha Brown Olmsted Pipestone Murray Cottonwood Watonwan Blue Earth Waseca Steele Dodge Winona Tick-borne disease risk in Minnesota is highest in forested areas within the shaded zones. Blacklegged ticks may also be found at lower levels in some forested areas outside this zone. Rock Nobles Jackson Martin Faribault Freeborn Mower Fillmore Houston Known high risk areas for tick-borne diseases, before 2004 Known high risk areas for tick-borne diseases, added in 2004

19 Recent Expansion of Disease Risk from Ixodes scapularis in Minnesota Base Map: University of Minnesota, Remote Sensing & Geospatial Analysis Laboratory

Rare or Emerging Tick-borne Diseases in Minnesota Agent

Lone star tick (Amblyomma americanum) Rocky Mountain

20 Rare or Emerging Tick-borne Diseases in Minnesota Agent Tick Vector Ehrlichiosis Ehrlichia spp. Lone star tick (Amblyomma americanum) Rocky Mountain spotted fever Rickettsia rickettsii Wood/dog tick (Dermacentor sp.) Powassan encephalitis Powassan virus (prototype and deer tick virus lineages) Blacklegged tick, Woodchuck tick (Ixodes spp.)

21 Climate Change and Tick-borne Disease Risk Increased temperature Increased precipitation/humidity - Longer tick growing/feeding season - Lower mortality in winter - New tick species - New disease agents - Increased blacklegged tick survival in warm season - Increased time available for tick feeding each day

22 Climate Change and Tick-borne Disease Risk (cont.) Increased forest habitat Increased host populations - More habitat for blacklegged ticks - More habitat for tick hosts (small and large mammals) - Higher tick populations - Easier establishment of ticks into new areas

23 Tick-borne Disease Prevention Personal protection (e.g., repellents- DEET, permethrin) Prompt medical care Vector control

24 Minnesota s Most Common Mosquito-borne Diseases West Nile virus disease LaCrosse encephalitis

25 West Nile Virus (WNV)

26 WNV Mosquito Vector in Minnesota: Culex tarsalis Image provided by Dale Parker

27 Culex tarsalis Distribution: widely distributed and abundant west of Mississippi River Habitat: temporary/semipermanent bodies of water (irrigated lands, ditches, hoof prints) Adults Moderate fliers, stay close to breeding place Hosts: wide range (prefer birds) Feeding: dawn and dusk ( crepuscular ) Survive overwinter

28 Culex tarsalis habitat

29 WNV: Epizootiology Mosquito vector Incidental infections West Nile virus Bird reservoir hosts Incidental infections

30 WNND County Level Incidence (cases/million), United States, 2003 Incidence per million >=100 Any WNV Activity *Reported as of 5/20/2004

31 Locally Acquired Human WNV Cases by County, Minnesota, (N = 362)

32 Human WNV Cases by Median Date of Illness Onset, Minnesota, Range 25-75% Quartiles Median Date 2007 (n=101) Year and Number of Cases 2006 (n=65) 2005 (n=45) 2004 (n=34) 2003 (n=148) 2002 (n=48) Jun Jul Aug Sep Oct Onset Date

33 LaCrosse Encephalitis (LAC) Vector: Tree-hole Mosquito (Aedes triseriatus)

34 LaCrosse Encephalitis (LAC) Aedes triseriatus (Eastern tree hole mosquito) primary LAC vector forest-dwelling mosquito Virus Viral amplification occurs during the summer from viremic chipmunks and squirrels Virus over-winters in mosquito eggs

35 Tree-hole Mosquito Habitat

36 Reported Cases of LaCrosse Encephalitis by County of Residence, Minnesota, Sherburne Brown 1 Sibley McLeod 1 Nicollet Wright 6 Blue Earth Carver 8 Le Sueur Hennepin 2 Scott Waseca 5 Anoka Rice 2 1 Washington Ramsey Dakota Steele 5 Goodhue Dodge 1 Olmsted Wabasha 6 Winona 14 Faribault Freeborn Mower Fillmore Houston * Cases include confirmed and probable cases (N = 124)

37 Risk of WNV and LAC When WNV Mid to late summer Dusk and dawn LAC Mid to late summer Daytime Where Western Minnesota Agricultural areas Southern Minnesota In or near woods and shelterbelts Who Elderly/immunecompromised Children < 16 years of age

38 Climate Change and Mosquito-borne Disease Risk Warmer and drier conditions Warmer/wetter conditions Changes in proportion of forest to agriculture land cover increased West Nile virus risk (enhanced virus amplification and greater vector production) increased Lacrosse encephalitis risk (longer virus amplification season, more vector habitat) changes in suitable habitat for vectors, hosts and disease agents leading to changes in human disease risk

39 Climate Change and Mosquitoborne Disease Risk (cont.) Potential emergence or re-emergence of exotic mosquito-borne diseases malaria Dengue fever Chikungunya Rift valley fever

40 Climate Change and Mosquitoborne Disease Risk (cont.) Potential increased survival of exotic mosquito species of public health importance Aedes albopictus (Asian tiger mosquito) Aedes japonicus (Japanese rock pool mosquito)

41 Mosquito-borne Disease: Bite Prevention = Disease Prevention Physical barriers Wear long pants, long sleeves Stay indoors when disease-carrying mosquitoes are active Ensure windows and doors have intact screens Repellents DEET, picaridin, oil of lemon eucalyptus, IR3535

42 Vector-borne Disease Risk: Human Factors Affected by Climate Change Movement of human populations (immigration of infected people) Human behavior (recreational, occupational) Changes in land use Public health infrastructure Emergence of drug or pesticide resistance

43 Vector-borne Disease and Climate Change Summary Climate change is likely to alter the geographic distribution and incidence of vector-borne diseases in Minnesota Depending on the extent of climate change and the specific disease, risk of illness will likely increase in some areas and decrease in others

44 For More Information Minnesota Department of Health

Vector-borne Diseases in Minnesota

Vector-borne Diseases in Minnesota David Neitzel, MS Hannah Friedlander, MPH Minnesota Department of Health Acute Disease Investigation and Control Morrison-Todd-Wadena Board of Health Meeting April 27,