The West Nile Virus – The West Nile Virus – A Global and Local ConcernA Global and Local Concern

Amleto A. Pucci, Jr. Ph.D. P.E.

Director, Bureau of Environmental Health

Bucks County Department of Health

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Outline

• Global Extent• United States Program• Science

– Vectors, hosts

– Transmission cycle

• Surveillance & Control• NYC Case study• Bucks County Data

West Nile OutbreaksWest Nile Outbreaks

• Uganda - 1937 (first diagnosed case)Uganda - 1937 (first diagnosed case)• Israel - 1951-1954, 1957, 2000Israel - 1951-1954, 1957, 2000• France - 1962, 2000France - 1962, 2000• South Africa - 1974South Africa - 1974• Romania – 1996Romania – 1996• Italy 1998Italy 1998• Russia - 1999Russia - 1999• United States –1999-2000United States –1999-2000

Modified from

West Nile Fever: Classical Clinical DescriptionWest Nile Fever: Classical Clinical Description

• Asymptomatic or mild dengue fever-like illnessAsymptomatic or mild dengue fever-like illness

• Fever, headache, abdominal pain, vomiting, rash, Fever, headache, abdominal pain, vomiting, rash, conjunctivitisconjunctivitis

• Incubation period usually 3 to 15 daysIncubation period usually 3 to 15 days

• CNS involvement and death in minority of casesCNS involvement and death in minority of cases

Modified from

West Nile Virus in the US West Nile Virus in the US Some Possible Pathways of IntroductionSome Possible Pathways of Introduction

• Infected human hostInfected human host• Human-transported vector(s) (agent) Human-transported vector(s) (agent) • Human-transported vertebrate host (carrier)Human-transported vertebrate host (carrier)

– LegalLegal– IllegalIllegal

• Storm-transported vertebrate host (bird)Storm-transported vertebrate host (bird)• Intentional introduction (terrorist eventIntentional introduction (terrorist event))

Partnerships for West Nile Virus in the Partnerships for West Nile Virus in the United StatesUnited States

• Centers for Disease Control and PreventionCenters for Disease Control and Prevention• U.S. Department of AgricultureU.S. Department of Agriculture• U.S. Geological SurveyU.S. Geological Survey• Department of DefenseDepartment of Defense• Environmental Protection AgencyEnvironmental Protection Agency• State and Local Health DepartmentsState and Local Health Departments• State and Local VeterinariansState and Local Veterinarians• State and Local Wildlife BiologistsState and Local Wildlife Biologists

New York CityNew York City

PhiladelphiaPhiladelphia

HoustonHouston

Los AngelesLos Angeles

Washington, D.C.Washington, D.C.

Jurisdictions Funded for Enhanced WN SurveillanceJurisdictions Funded for Enhanced WN Surveillance

First Round $$First Round $$

Second Round $$Second Round $$

West Nile Fever: Background and EpidemiologyWest Nile Fever: Background and Epidemiology

• Basic transmission cycle involves mosquitoes Basic transmission cycle involves mosquitoes feeding on birds infected with the West Nile virusfeeding on birds infected with the West Nile virus

• Infected mosquitoes then transmit West Nile virus Infected mosquitoes then transmit West Nile virus to humans and animals when taking a blood mealto humans and animals when taking a blood meal

Modified from

Virus

• Virus uses birds as amplifier hosts, with vectors that feed on birds.

• Virus strain is highly infectious for North American birds, causing mortality and high viremia.

• Virus does not transmit from infected mosquito to next mosquito generation.

• Virus overwinters in some mosquitoes.

West Nile Virus Transmission Cycle

Modified from

Estimated Sensitivity of West Nile Virus Estimated Sensitivity of West Nile Virus Surveillance MethodsSurveillance Methods

Human cases

Veterinary cases

Mosquitoes,

Dead bird

Time

Dis

eas

e A

cti

vit

y

Surveillance method

sentinel hosts

Integrated Mosquito Management• Surveillance

– Bird– Mosquito– Human

• Larval Mosquito Control– Source reduction– Appropriate response to the need

• Adult Mosquito Control– Targeted Approach – based on field data

• Education - Outreach

Mosquito Trap methods used by West Nile Virus Program Bucks County Department of Health,

Gravid TrapABC Mosquito Light Trap

Modified Aspirator

Types of Mosquito Control used in the Bucks County West Nile Virus Program

• Bti (Bacillus thuringiensis isrealensis) – naturally occurring soil bacteria which disrupts the gut of the larvae– Essentially nontoxic to humans– Does not effect wildlife and non-target species

• Methoprene “Altocid” -- chemical growth regulator– Low toxicity to mammal, birds, and fish. – Some invertebrates are sensitive to it therefore strictly

controlled.– Not unreasonable risk to the environment. Breaks

down quickly.

1999 WN virus activity in NYC area1999 WN virus activity in NYC area1999 WN virus activity in NYC area1999 WN virus activity in NYC area

MosquitoesMosquitoes

BirdsBirds

HumansHumans

Bucks County West Nile Virus Positive Dead Birds in 2000 and 2001 ( through 10/17/01)

0

5

10

15

20

25

30

35

Municipality in Bucks County, PA

Dea

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ird

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Dead Birds perTownship in 2000

Dead BirdsperTownship in 2001

Municipality series is approximately from southeast towards nortwest within Bucks County

Bucks County West Nile Virus Positive Dead Birds in 2001 per Twp Sq. Mi ( through 10/17/01)

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2

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3

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Municipality in Bucks County, PA

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in 2001

Municipality series is approximately from southeast towards nortwest within Bucks County

Select West Nile Virus Research Priorities

• Virus persistence mechanisms (disease reservoir)• Vector (mosquito species) relationships and range

– Mosquito biology and behavior

• Vertebrate host (birds) relationships and range – Bird migration as dispersal mechanism

• Current & future geographic WNV distribution• Development of preventative strategies

– Improved lab diagnostic tests– Clinical studies of human infections– Vaccine development

Key Messages

• Best thing is to eliminate places where mosquitoes breed.

• Public Health is working hard to reduce mosquito populations in Bucks County.

• If you have questions call West Nile Virus Hotline (1-877-PAHEALTH), and contact your physician.