WEST NILE VIRUS

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WEST NILE VIRUS
Surveillance and Control
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West Nile Virus Background and Ecology

• First isolated in West Nile district, Uganda,
  1937
• Commonly found in humans and birds and other
  vertebrates in Africa, Eastern Europe, West Asia,
  and the Middle East, but has not previously been
  documented in the Western Hemisphere
• Basic transmission cycle involves mosquitoes
  feeding on birds infected with the West Nile
  virus
• Infected mosquitoes then transmit West Nile virus
  to humans and animals when taking a blood meal

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West Nile Virus Outbreaks

• Israel 1951-1954, 1957, 2000
• France 1962, 2000
• South Africa 1974
• Romania 1996
• Italy 1997
• Russia 1999
• U. S. A. 1999-2002

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Spread of West Nile Virus in the U.S. 7/30/02
1999
2000
2001
Humans
2002
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WNV Case-Patient Demographics Mortality United
States, 1999-2001
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Date of Symptom Onset, West Nile VirusUnited
States, 1999-2001
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Clinical Epidemiology

• Incubation period 3 - 14 days
• 20 develop West Nile fever
• 1 in 150 develop meningoencephalitis
• Advanced age primary risk factor for severe
  neurological disease and death

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West Nile Fever Classic Clinical Description

• Mild flu-like illness of sudden onset
• Duration 3 - 6 days
• Fever, swollen lymph nodes, headache, abdominal
  pain, vomiting, rash, conjunctivitis, eye pain,
  anorexia
• Symptoms of West Nile fever in contemporary
  outbreaks not fully studied

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Symptoms of Hospitalized Patients withWest Nile
Virus
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Fever
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Weakness
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Nausea
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Vomiting
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Headache
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Change in mental status
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Diarrhea
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Rash
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Swollen Lymph Nodes
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Risk of West Nile Virus Transmission Through
Blood Transfusion

• Concern most WNV infections have no or only mild
  symptoms, and transient viremia occurs after
  infection
• Transfusion-transmission of WNV or other related
  flaviviruses not reported, but plausible
• Mathematical modeling estimated risk of
  transfusion-transmission was 2 in 10,000 during
  NYC outbreak (Transfusion, Aug 2002)
• WNV should be considered in persons who develop
  unexplained fever, meningitis, or encephalitis
  after transfusion

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West Nile Virus
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Mosquitoes

• Usually Culex Genus
• Pipiens or Restuans species are most common
  carriers in this area
• Only the females bite
• Males feed on nectar
• Normally only ¼ long
• Huge mosquitoes are really crane flies

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Mosquito Lifecycle

• Egg raft
• Up to 300 eggs
• Hatch within 3 days
• Larvae
• Wigglers
• Pupae
• Tumblers
• Become adults within a few days
• Adult
• Males Live one week
• Females live one month
• Flight range up to ½ mile

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West Nile VirusTransmission Cycle

• Mosquito infects bird while taking a blood meal
• Other mosquitoes pick up the virus from the
  infected bird
• Humans and animals (horses) get the virus from
  infected mosquitoes
• ONLY MOSQUITOES CAN SPREAD WEST NILE VIRUS

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West Nile VirusTransmission Cycle
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Dead Birds

• Virus found in over 100 species of birds
• Predominant species
• Hawks
• Owls
• Crows
• Blue jays
• Call 1-877-PA HEALTH
• Only five birds are tested weekly

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Hawks

• Length 18 inches Wingspan 48 inches
• Short, dark, hooked beak
• Large, broad-winged, broad-tailed hawk
• Immatures have notably narrower wings and tail,
  and appear slimmer
• Dark patagial mark on underwing, present on all
  ages and races, is unique

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Owls

• Length 8 inches Wingspan 22 inches
• Small, nocturnal, predatory bird
• Large, rounded head with ear tufts
• Yellow eyes
• Dense streaking on underparts with finer barring
• Some birds have rusty plumage, others dark gray

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Bluejays

• Length 10 inches
• Black sturdy bill
• Blue crest and upperparts
• Black eyeline and breastband
• Grayish-white throat and underparts
• Bright blue wings with black bars and white
  patches
• Long blue tail with black bars and white corners
• Dark legs

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Crows

• Length 17 inches
• Entirely black plumage
• Squared-off tail
• Very common in urban and agricultural areas

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Washington CountyWNV Program

• Surveillance of known problem areas
• Surveillance of citizen complaints
• Samples sent to PA DOH for analysis
• Positive areas are treated
• Heavily infested areas are treated
• Purpose is not to eradicate the mosquito
  population

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West Nile Virus Surveillance
Dead Bird Reports Dead Bird Testing Live Bird
Testing Mosquito Testing Equine Cases Human
Cases
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Gravid Trap

• Lactalbumin water is an attractant
• Draws mosquitoes into trap from the bottom
• Easier to use
• More effective than light traps

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Gravid Trap
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Light Trap

• Carbon dioxide and light used as attractants
• Color
• Collection bin hangs from the bottom

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PREVENTION
West Nile Virus Human Cases
MosquitoControl
PersonalProtection
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Personal Protection Clothing

• Avoid black and white
• Wear long sleeves
• Wear long pants

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Personal ProtectionAvoidance

• Home needs to be Bug Tight
• Stay indoors at dusk and dawn
• Use insecticides at dusk and dawn
• Use white incandescent lights
• Vitamin B, Bug Zappers, and ultrasonic
  devices are ineffective

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Personal Protection

• Repellant
• Deet
• Bite Blocker
• Avon Skin So Soft
• Read and understand label directions
• Apply lightly to skin and clothing

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Mosquitoes Can Kill
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Mosquito Control
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• Mosquito Control
• Habitat Elimination
• Adulticiding
• Larviciding

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Adulticiding

• Malathion
• Organophosphate
• Applied in Ultra Low Volume
• Can be toxic to humans
• Originally, only done for positive test areas
• Will be done for heavy infestations

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Larviciding

• Preferred method of control
• Microbial BTI, CG, and WDG
• Naturally occurring bacteria
• Non-toxic to humans and animals
• Methoprene
• Growth regulating hormone
• Applied to ditches, ponds, marshes
• Temephos
• Organophosphate pesticide
• Can pose a human health hazard
• Monomolecular films Oils
• Causes larvae and pupae to drown
• Poses little risk to humans, wildlife, and the
  environment

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Natural Predators

• Purple Martins
• Bats
• Mosquito fish
• Other breeds of mosquitoes
• Mosquitoes are not the meal of choice

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Habitat

• Catch basins
• Clogged bodies of water
• Construction depressions
• Flooded Flower pots
• Public dumps
• Birdbaths
• Unfiltered swimming pools

• Cemetery urns
• Clogged rain gutters
• Boats
• Rain barrels
• Hoof prints
• Swamps
• Tree holes
• Tin cans
• Tires

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Control Breeding Sites

• Turn over pools and wheel barrows
• Dispose of things that can hold water i.e. tires,
  tin cans, broken toys, etc.
• Drill holes in permanent containers
• Clean clogged roof gutters
• Empty accumulated water from boats
• Keep outdoor water fresh
• Landscape your property
• Keep grass cut and weeds pulled

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QUESTIONS?

• THANK YOU!