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

West Nile Virus OutbreaksWest Nile Virus Outbreaks

Israel –Israel – 1951-1954,1951-1954, 19571957, , 20002000 France –France – 1962, 20001962, 2000 South Africa –South Africa –19741974 Romania –Romania – 19961996 Italy –Italy – 19971997 Russia –Russia – 19991999 U. S. A. –U. S. A. – 1999-20021999-2002

Humans200120001999

2002

Spread of West Nile Virus in the U.S. Spread of West Nile Virus in the U.S. 7/30/027/30/02

WNV Case-Patient Demographics & Mortality United States, 1999-2001

1999 - 20001999 - 2000 20012001

NumberNumber 8383 6666

Age (yr)Age (yr)

medianmedian 6565 6868

rangerange 5 - 905 - 90 19 - 9019 - 90

MalesMales 54%54% 65%65%

CFRCFR 11%11% 14%14%

Date of Symptom Onset, West Nile VirusDate of Symptom Onset, West Nile VirusUnited States, 1999-2001United States, 1999-2001

0

5

10

15

20

25

30

7/7

8/4

9/1

9/29

10/2

711

/24

12/2

3

Week ending

Nu

mb

er

of

ca

se

s

2001

2000

1999

Clinical EpidemiologyClinical Epidemiology

Incubation period 3 - 14 daysIncubation period 3 - 14 days

20% develop “West Nile fever”20% develop “West Nile fever”

1 in 150 develop meningoencephalitis1 in 150 develop meningoencephalitis

– Advanced age primary risk factor for Advanced age primary risk factor for severe neurological disease and deathsevere neurological disease and death

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

Symptoms of Hospitalized Patients withSymptoms of Hospitalized Patients withWest Nile VirusWest Nile Virus

2%2%Swollen Lymph NodesSwollen Lymph Nodes

19%19%RashRash

27%27%DiarrheaDiarrhea

46%46%Change in mental statusChange in mental status

47%47%HeadacheHeadache

51%51%VomitingVomiting

53%53%NauseaNausea

56%56%WeaknessWeakness

90%90%FeverFever

West Nile VirusWest Nile Virus

MosquitoesMosquitoes

Usually Culex GenusUsually Culex Genus Pipiens or Restuans species are most common Pipiens or Restuans species are most common

carriers in this areacarriers in this area Only the females biteOnly the females bite Males feed on nectarMales feed on nectar Normally only ¼ “ longNormally only ¼ “ long ““Huge” mosquitoes are really crane fliesHuge” mosquitoes are really crane flies

Mosquito LifecycleMosquito Lifecycle

Egg raftEgg raft Up to 300 eggsUp to 300 eggs Hatch within 3 daysHatch within 3 days

LarvaeLarvae WigglersWigglers

PupaePupae TumblersTumblers Become adults within a few daysBecome adults within a few days

AdultAdult Males Live one weekMales Live one week Females live one monthFemales live one month Flight range up to ½ mileFlight range up to ½ mile

West Nile VirusWest Nile VirusTransmission CycleTransmission Cycle

Mosquito infects bird while taking a Mosquito infects bird while taking a “blood meal”“blood meal”

Other mosquitoes pick up the virus Other mosquitoes pick up the virus from the infected birdfrom the infected bird

Humans and animals (horses) get the Humans and animals (horses) get the virus from infected mosquitoesvirus from infected mosquitoes

ONLY MOSQUITOES CAN SPREAD ONLY MOSQUITOES CAN SPREAD WEST NILE VIRUSWEST NILE VIRUS

West Nile VirusWest Nile VirusTransmission CycleTransmission Cycle

Dead BirdsDead Birds

Virus found in over 100 species of Virus found in over 100 species of birdsbirds

Predominant species:Predominant species:– HawksHawks– OwlsOwls– CrowsCrows– Blue jaysBlue jays

Call 1-877-PA HEALTHCall 1-877-PA HEALTH Only five birds are tested weeklyOnly five birds are tested weekly

HawksHawks Length: 18 inches Length: 18 inches

Wingspan: 48 inches Wingspan: 48 inches Short, dark, hooked Short, dark, hooked

beak beak Large, broad-winged, Large, broad-winged,

broad-tailed hawk broad-tailed hawk Immatures have notably Immatures have notably

narrower wings and tail, narrower wings and tail, and appear slimmer and appear slimmer

Dark patagial mark on Dark patagial mark on underwing, present on underwing, present on all ages and races, is all ages and races, is uniqueunique

OwlsOwls Length: 8 inches Length: 8 inches

Wingspan: 22 inches Wingspan: 22 inches Small, nocturnal, Small, nocturnal,

predatory bird predatory bird Large, rounded head Large, rounded head

with ear tufts with ear tufts Yellow eyes Yellow eyes Dense streaking on Dense streaking on

underparts with finer underparts with finer barring barring

Some birds have rusty Some birds have rusty plumage, others dark plumage, others dark gray gray

BluejaysBluejays Length: 10 inches Length: 10 inches Black sturdy bill Black sturdy bill Blue crest and upperparts Blue crest and upperparts Black eyeline and Black eyeline and

breastband breastband Grayish-white throat and Grayish-white throat and

underparts underparts Bright blue wings with Bright blue wings with

black bars and white black bars and white patches patches

Long blue tail with black Long blue tail with black bars and white corners bars and white corners

Dark legs Dark legs

CrowsCrows

Length: 17 inches Length: 17 inches

Entirely black Entirely black plumage plumage

Squared-off tail Squared-off tail

Very common in Very common in urban and urban and agricultural areas agricultural areas

Washington CountyWashington CountyWNV ProgramWNV Program

Surveillance of known problem areasSurveillance of known problem areas Surveillance of citizen complaintsSurveillance of citizen complaints Samples sent to PA DOH for analysisSamples sent to PA DOH for analysis Positive areas are treatedPositive areas are treated Heavily infested areas are treatedHeavily infested areas are treated Purpose is not to eradicate the Purpose is not to eradicate the

mosquito populationmosquito population

Dead Bird Reports

Dead Bird Testing

Live Bird Testing

Mosquito Testing

Equine Cases

Human Cases

West Nile Virus SurveillanceWest Nile Virus Surveillance

Gravid TrapGravid Trap

Lactalbumin water is an attractantLactalbumin water is an attractant Draws mosquitoes into trap from the Draws mosquitoes into trap from the

bottombottom Easier to useEasier to use More effective than light trapsMore effective than light traps

Gravid TrapGravid Trap

Light TrapLight Trap

Carbon dioxide and Carbon dioxide and light used as light used as attractantsattractants

ColorColor Collection bin Collection bin

hangs from the hangs from the bottombottom

West Nile Virus – Human Cases

MosquitoMosquitoControlControl

PersonalPersonalProtectionProtection

PREVENTIONPREVENTION

Avoid black and whiteWear long sleevesWear long pants

Personal Protection

Clothing

•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

Personal ProtectionAvoidance

•Repellant

DeetBite BlockerAvon Skin So Soft

•Read and understand label directions

•Apply lightly to skin and clothing

Personal Protection

Mosquito ControlMosquito Control

Mosquito Control

Habitat Elimination

Adulticiding

Larviciding

AdulticidingAdulticiding

MalathionMalathion OrganophosphateOrganophosphate Applied in “Ultra Low Volume”Applied in “Ultra Low Volume” Can be toxic to humansCan be toxic to humans

Originally, only done for positive test Originally, only done for positive test areasareas

Will be done for Will be done for heavyheavy infestations infestations

LarvicidingLarviciding Preferred method of controlPreferred method of control Microbial – BTI, CG, and WDGMicrobial – BTI, CG, and WDG

Naturally occurring bacteriaNaturally occurring bacteria Non-toxic to humans and animalsNon-toxic to humans and animals

MethopreneMethoprene Growth regulating hormoneGrowth regulating hormone Applied to ditches, ponds, marshesApplied to ditches, ponds, marshes

TemephosTemephos Organophosphate pesticideOrganophosphate pesticide Can pose a human health hazardCan pose a human health hazard

Monomolecular films & OilsMonomolecular films & Oils Causes larvae and pupae to drownCauses larvae and pupae to drown Poses little risk to humans, wildlife, and the Poses little risk to humans, wildlife, and the

environmentenvironment

Natural PredatorsNatural Predators

Purple MartinsPurple Martins BatsBats Mosquito fishMosquito fish Other breeds of mosquitoesOther breeds of mosquitoes

Mosquitoes are Mosquitoes are notnot the meal the meal of choiceof choice

HabitatHabitat

Catch basinsCatch basins Clogged bodies of Clogged bodies of

waterwater Construction Construction

depressionsdepressions Flooded Flower potsFlooded Flower pots Public dumpsPublic dumps BirdbathsBirdbaths Unfiltered swimming Unfiltered swimming

poolspools

Cemetery urnsCemetery urns Clogged rain guttersClogged rain gutters BoatsBoats Rain barrelsRain barrels Hoof printsHoof prints SwampsSwamps Tree holesTree holes Tin cansTin cans TiresTires

Control Breeding SitesControl Breeding Sites

Turn over pools and wheel barrowsTurn over pools and wheel barrows Dispose of things that can hold water Dispose of things that can hold water

i.e. tires, tin cans, broken toys, etc.i.e. tires, tin cans, broken toys, etc. Drill holes in permanent containersDrill holes in permanent containers Clean clogged roof guttersClean clogged roof gutters Empty accumulated water from boatsEmpty accumulated water from boats Keep outdoor water freshKeep outdoor water fresh Landscape your propertyLandscape your property Keep grass cut and weeds pulledKeep grass cut and weeds pulled

QUESTIONS?QUESTIONS?

THANK YOU!THANK YOU!