Mosquito-borne Diseases

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Mosquito-borne
Diseases
In Washington
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Mosquito-borne Diseases
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• Western equine encephalitis and St. Louis
  encephalitis
• Both have occurred in Washington but no reported
  cases since early 1980s
• West Nile virus
• Detected in 1999 in New York City
• Detected in Washington and 43 other states in
  2003
• Continued surveillance effort in Washington

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Mosquito-borne Disease Surveillance
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• Pre-1960s No record of state activity
• 1960s First statewide mosquito survey
  published in 1966
• 1960s Mosquito Control Districts formed in
  Eastern Washington
• 1970s Sentinel flocks used in Benton County
  and Grant County

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Mosquito-borne Disease Surveillance
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• 1980s Last confirmed human and horse cases of
  mosquito-borne encephalitis
• 1990s Zoonotic Disease program established
  in DOH
• 2001 DOH initiates WNV surveillance

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Yakima Valley Encephalitis Outbreaks
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• 1939 31 cases
• 1940 58 cases 13 fatal
• 1941 26 cases 3 fatal
• 1942 28 cases 2 fatal
• (Reported in August 1945 Journal of American
  Medical Association)

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Reported Human Cases of Mosquito-borne Disease
(1970-1982)
Island
San Juan
Whatcom
Pend Oreille
Ferry
Skagit
Okanogan
Stevens
Snohomish
Clallam
Chelan
Jefferson
Spokane
Douglas
Kitsap
King
Lincoln
Grays Harbor
Mason
Grant
Kittitas
Whitman
Adams
Pierce
Thurston
Yakima 7 Cases ( 6 WEE, 1 SLE)
Franklin
Lewis
Garfield
Pacific
Columbia
Skamania
Walla Walla
Cowlitz
Benton
Asotin
Klickitat
Wahkiakum
Clark
Western Equine Encephalitis
St. Louis Encephalitis
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Total cases 12
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Western Equine Encephalitis Horse
Cases (1953-1983)
Island
San Juan
Whatcom
Pend Oreille
Ferry
Okanogan
Skagit
Stevens
Snohomish
Clallam
Chelan
Jefferson
Spokane
Douglas
Kitsap
King
Lincoln
Grays Harbor
Mason
Grant
Adams
Kittitas
Whitman
Pierce
Thurston
Yakima
Franklin
Lewis
Garfield
Pacific
Columbia
Walla Walla
Cowlitz
Benton
Skamania
Asotin
Klickitat
Wahkiakum
Clark
Suspect cases
Confirmed cases
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West Nile VirusIn the United States
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WNV Background
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• First isolated in the West Nile District of
  Uganda, 1937
• Recognized as a cause of inflammation of the
  spinal cord and brain with outbreak in elderly
  patients, Israel, 1957
• Equine disease noted in Egypt and France in the
  early 1960s
• 1999 Old World virus arrives in the New World

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West Nile Outbreaks
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• Israel 1951-1954, 1957, 2000-2002
• France 1962, 2000
• South Africa 1974
• Romania 1996-1997
• Italy 1997
• Czech Republic 1998
• Republic of the Congo 1998
• Russia 1999
• United States 1999-2002

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Outbreak Timeline
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Encephalitis Condition Identified
Equine Disease Identified
Israel 1957
Uganda 1937
Israel 1951-54
France 1962
South Africa 1974
Romania 1996 Italy 1997 Czech Rep. 1998 Congo
1998 Russia 1999 US 1999-2002 Israel
2000-2002 France 2000
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West Nile Virus Transmission Cycle
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Mosquito vector
Incidental infections
Incidental infections
Bird reservoir hosts
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WNV in the US Speculated Pathways of Introduction
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• Human-transported bird
• Legal
• Illegal
• Human-transported mosquitoes
• Storm-transported bird
• Intentional introduction (terrorist event)-not
  likely
• Infected human traveler-not likely

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WNV Symptoms
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• High Fever
• Headache and body aches
• Skin rash
• Swollen lymph glands
• Neck stiffness
• Disorientation
• Convulsions

The incubation period for West Nile Virus is
generally 3-14 days following a bite from an
infected mosquito.
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Distribution of WNV Before 1999
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States with WNV (0)
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Distribution of WNV as of November 1999
States with WNV (4)
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Distribution of WNV as of November 2000
States with WNV (12 DC)
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Distribution of WNV as of November 2001
States with WNV (27 DC)
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Distribution of WNV as of November 2002
States with WNV (44 DC)
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WNV 1999-2002 by County
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Distribution by County December 7, 2002
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Source Dr. Henry Huang, Washington U. School of
Medicine
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Counties Detecting West Nile Virus 2002
Whatcom
San Juan
Island
Okanogan
Pend Oreille
Ferry
Skagit
Stevens
Clallam
Snohomish
Chelan
Jefferson
Douglas
Spokane
Kitsap
Lincoln
King
Mason
Grays Harbor
Grant
Kittitas
Pierce
Adams
Whitman
Thurston
Pacific
Lewis
Garfield
Franklin
Yakima
Columbia
Asotin
Cowlitz
Benton
Walla Walla
Skamania
Wahkiakum
Klickitat
Clark
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Case Summary 1999-2002
Year Humans (deaths) Horses (deaths)
2002 4,161 (277) 14,717
2001 66 (9) 470 (156)
2000 21 (2) 60 (23)
1999 62 (7) 25 (8)
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WNV Case-Patient Demographics Mortality United
States, 1999-2002
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As of Dec 19
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Date of Symptom Onset, West Nile VirusUnited
States, 1999-2001
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Protecting Public Health

• Surveillance
• Personal Protection and Education
• Mosquito Control

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WNV Surveillance
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• Mosquitoes
• Dead birds (especially crows, jays, ravens and
  magpies)
• Veterinary surveillance
• Human surveillance

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Mosquito Surveillance
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• Review information on species in your
  jurisdiction
• Establish system for recording mosquito
  complaints
• Identify and map breeding locations
• Conduct larval/adult surveillance (May-Sep)

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Dead Bird Surveillance
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• Establish system for recording dead bird reports
• Message to public on reporting sightings
• Submit corvids for analysis (May-Oct)
• Response protocol for positive birds

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Horse Case Surveillance
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• Encourage reporting by local veterinarians
• Identify major stables, training facilities and
  establish contact
• Track cases as they occur
• Response protocol for sick, dead horses

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Human Case Surveillance
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• Enhanced passive surveillance May-Sep
• Active surveillance when cases result
• Case investigation to help define probable
  exposure
• Response protocol for illness or death in humans

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Mosquito Control
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• Assessment of local capability
• Designation of lead agency, person (where, when,
  how)
• Develop local action plan
• Training and licensing of personnel to use
  mosquito control compounds
• Keep community involved and informed in the
  decision process, especially if adulticiding is
  considered

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WNV Mosquito Species in Washington
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• Aedes cinereus
• Aedes vexans
• Culex pipiens
• Culex restuans
• Culex tarsalis
• Anopheles punctipennis
• Coquilletidia perturbans
• Ochlerotatus canadensis
• Ochlerotatus japonicus

• Counties (39)
• 22
• 27
• 28
• 1
• 35
• 26
• 10
• 5
• 1

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Estimated Sensitivity of WNV Surveillance Methods
Human cases
Veterinary cases
Mosquitoes
Disease Activity
Sentinel hosts
Dead birds
Time
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Personal Protection
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• Wear long sleeves pants in mosquito-infested
  areas
• Use repellant containing DEET (N,N-diethyl-3-methy
  lbenzamide) and follow directions carefully
• Limit outdoor activities at dawn and early
  evening
• Repair holes in door window screens

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Habitat Reduction
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• Eliminate standing water (flower pots tires
  wheelbarrows wading pools)
• Change the water in birdbaths at least weekly
• Aerate and chlorinate swimming pools and hot
  tubs cover if possible
• Consider mosquito-eating fish for your pond
• Keep gutters clean to prevent standing water
• Spread the word educate your friends and
  neighbors

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Want More?
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• www.doh.wa.gov/wnv
• www.cdc.gov
• www.cfe.cornell.edu/erap/WNV/
• www.mrsc.org/subjects/governance/spd/mosquito.aspx
  
• Your local health department