West Nile Virus

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West Nile Virus

• Greg Chrislip
• Public Health Entomologist
• WV Department of Health and Human Resources

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Other bloodsucking insects merely annoy,
but mosquitoes insult. By night, these slow
decadent flies whine around our heads, always
vanishing when the light goes on. By day, they
dont even pay us the respect of evasive action,
content to be smeared across our exteriors in
stains of protoplasm rather than curtail their
orgies
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Stay your hand, bear the sting, and watch as she
deliberately probes with her six stilettos,
injects anticoagulant, swills your blood until
her abdomen resembles a ripe aneurysm, voids on
your skin, and finally raises a hind leg in
doglike salute. Audubon Incite,
October 2001
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How Much Activity in 2002?Reported to CDC and
Verified as of 15 April 2003
44 States and DC

• Dead Birds
• Seroprevalence (birds)
• Captive sentinel animals
• Mosquito pools
• Veterinary
• Human

• 16,739
• 270
• 1640
• 6,604
• 14,571
• 4,156 (284 deaths)

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CDC Website
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New Modes Of Transmission in 2002

• Transplant Recipients
• Blood Transfusion
• Transplacental
• Breast Milk
• Occupational Exposure

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West Virginia West Nile Surveillance 2002

• From May 1 November 30, 2002 the LHDs have
  reported 6,952 dead birds to the Infectious
  Disease Epidemiology Program.
• 253 Crows and 6,699 other species

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West Virginia West Nile Surveillance 2002

• From May 1 to November 30, 2002 a total of 903
  dead birds have been submitted to the
  Southeastern Cooperative Wildlife Disease Study
  (SCWDS) at the University of Georgia or the
  National Wildlife Health Center in Madison, WI
  for virus testing.

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West Virginia West Nile Dead Bird Surveillance
2002

• 77 - Positive for West Nile virus
• 763 - Negative for West Nile virus
• 30 - Not Tested (received by lab too
  deteriorated to test)
• 18 status unknown, do not know if sent, lost in
  mail, lost at lab, etc.
• Total 903

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West Virginia West Nile Surveillance 2002

• Three positive horses have been identified in the
  state (Mercer, Cabell and Jefferson counties).
• Three positive human cases
• (1 Putnam and 2 Wood counties)

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Dead Bird Surveillance
Dead Bird Surveillance 2003
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2003 Dead Bird Testing

• Test 1,000 dead birds at the Southeastern
  Cooperative Wildlife Disease Study (SCWDS)
• ALL SPECIES of dead birds with no obvious signs
  of trauma will be acceptable.
• Fresh specimens, less than 24 hours old, without
  signs of decay should be sent in.

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Mosquito Surveillance
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Objectives

• Identification of the mosquito species that are
  present in an area.
• Determining whether they are important WNV vector
  species.
• Identification and mapping of mosquito breeding
  habitats for larval control purposes.
• Defining the geographic area affected by
  mosquitoes originating from identified habitats.

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Objectives (cont.)

• Determining the population density.
• Determining when mosquito populations are at the
  appropriate developmental or behavioral stage to
  apply control measures.
• Determining the effectiveness of local mosquito
  control measures.

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Objectives (cont.)

• Determining whether vector mosquito species are
  present in an area whether they are infected
  with arboviruses.
• Determining the mosquito infection rate for
  arboviruses in vector species populations.
• Determining the seasonal activity patterns of
  local mosquito species.

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Mosquito Biology

• 4 distinct stages in their lifecycle
• Egg, larva, pupa and adult
• Most females blood feed
• Over 3,000 species world-wide

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Female Mosquito (Cx. quinquefasciatus) Blood
Feeding on a finger
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Culex Mosquito laying eggs
Egg raft
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Siphon
Culextype Mosquito Larvae wigglers
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Mosquito Pupae tumblers
trumpets
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2002 Mosquito Surveillance

• A total of 25 species are shown to be positive
  for West Nile virus in 2002.
• 11 additional species of mosquitoes were positive
  for the virus in previous years (1999- 2001)
• Total number of mosquito species testing positive
  for West Nile Virus 36

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2002 Mosquito Surveillance

• Genera that tested positive included
• Aedes (4 species), Anopheles (6 species),
  Coquillettidia (1 species), Culex (8 species),
  Culiseta (2 species), Deinocerites (1 species)
  Ochlerotatus (9 species), Orthopodomyia (1
  species), Psorophora (3 species), and Uranotaenia
  (1 species).

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Surveillance

• Identifies locations where mosquito populations
  may be increasing.
• Allows identification of potential vector
  species.
• Adult surveillance can assist in pinpointing
  larval sites.
• Adult surveillance
• CDC Gravid Traps
• CDC Miniature Light Traps
• Larval Surveillance
• Dippers and turkey basters

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Larval Surveillance

• Assist with locating breeding sites after the
  finding of a positive human, bird or animal.
• Collecting and submitting samples for
  identification.
• Larval identification class.

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Adult Surveillance

• Assist with locating breeding sites after the
  finding of a positive human, bird or animal.

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2003 Mosquito Surveillance

• Larval collections around positive West Nile and
  La Crosse cases.
• Test 1,000 mosquito pools at the Southeastern
  Cooperative Wildlife Disease Study (SCWDS).

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Full understanding of WNV, its prevention and
control, is a multidisciplinary
challenge-involving such diverse fields as
entomology, ecology, poultry science,
ornithology, meteorology, the military,
epidemiology, public health, pest control, the
trade in used tires, race horses, global warming,
and risk communication. Cornell Environmental
Update, Autumn 2001

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