Docstoc

West Nile - U of A Division of A

Document Sample
West Nile - U of A Division of A Powered By Docstoc
					West Nile Virus Update

    John D. Hopkins, Ph.D.
    Extension Urban Entomologist
What is West Nile Virus?
 “arbovirus” - derived from phrase
  “arthropod-borne.”
 Flavivirus
 Infects birds, humans, other vertebrates
  (Africa, E. Europe, W. Asia, Middle East.)
 Closely related to St. Louis encephalitis
  virus found in US.
Geographic Distribution of the Japanese Encephalitis
      Serocomplex (Family Flaviridae), 2000
West Nile Virus
 Wild and domestic birds - primary host.
 Spreads from birds to man and other
  animals via mosquitoes feeding on an
  infected bird and then biting another host.
 Mosquitoes that transmit WNV and SLE
  usually prefer to bite birds.
 Human infections with these mosquito-
  borne viruses are very rare and can be
  prevented by taking simple measures to
  avoid mosquito bites.
West Nile Virus Transmission Cycle
Symptoms: WN fever / encephalitis
   Usually 3-15 days after bite of infected mosquito.
   Most people infected with WNV have no symptoms
   Or - may have mild flu-like illness (West Nile Fever)
       fever, headache, and body aches

       completely recover (few days).

   Or - serious illness with inflammation of brain
    (WN Encephalitis)
       particularly at risk are the elderly (> 50 yrs old)

       high fever, severe headache, nausea, stiff neck,
        confusion, muscle weakness, paralysis,
        disorientation, convulsions, coma, and rarely, death.
   < 1% of humans infected with WNV will develop serious
    illness.
WNV Transmission Risk

Late Summer
Early Fall

 Year Round


Late Summer
Early Fall



In temperate zone (between lat. 23.5° and 66.5° N and S),
WNV is transmitted primarily in the late summer or early fall.
In the equatorial climates WNV can be transmitted year round.
Treatment: WN fever / encephalitis
 No specific treatment, medication, or cure for
  illnesses caused by West Nile virus
 Symptoms and complications of the disease
  can be treated
 No vaccine currently available for humans
 Vaccine available for horses (conditionally
  licensed by the USDA in August 2001).
  Symptoms in horses are similar to symptoms
  found in horses infected with EEE.
    History of West Nile Virus
   1st discovered West Nile District of Uganda 1937
   Israel - 1951-1954, 1957 large outbreak, 2000
   France – 1962, 2000
   South Africa - 1974
   Romania - 1996
   Italy - 1998
   Russia - 1999
    History of West Nile Virus

   WNV 1st recognized in Western Hemisphere
    summer 1999
      outbreak occurred in New York City area

      62 people diagnosed with WNV

      7 deaths.
How was WNV introduced into US?
 Origin of WNV in US unknown, but most
  closely related genetically to strains found
  in Middle East.
 Possible Pathways of Introduction:
    Infected human host

    Human-transported vertebrate host

       Legal or Illegal

    Human-transported vector(s)

    Storm-transported vertebrate host (bird)

    Intentional introduction (terrorist event)
History of West Nile Virus (continued)


    WNV spread in 2000:
      District of Columbia and 12 states (CT,

       DE, MD, MA, NH, NJ, NY, NC, PA, RI,
       VT, and VA)
      21 human cases WN encephalitis (NY,
       NJ, and CT) with 2 deaths
History of West Nile Virus (continued)
   Sept. 2001:
     4 blue jays with
      WNV (Union,
      Saline, and
      Sebastian Co’s in
      AR)
     No human WNV
      cases yet
      diagnosed in AR
History of West Nile Virus (continued)


   October 2001:
     WNV present in 27 states and Canada
   WNV-Positive Dead Birds, 2001*


             7,338 birds
                               DC
             328 counties
             27 states & DC




* As of 3/13/2002
History of West Nile Virus (continued)

    2001 - human infection with WNV:
       10 states

       66 cases

       9 deaths.
 Human WNV Disease Cases, 2001*



                    66 cases
                    39 counties
                    10 states




* As of 3/13/2002
History of West Nile Virus (continued)
   2002: WNV activity spread to most states
        West Nile Virus Map -- October 2002
History of West Nile Virus (continued)
   2002: 3242 human cases 176 deaths
What’s being done about WNV in AR?
   CDC provided grant to Arkansas Dept. of Health
    to enhance WNV and other arbovirus
    surveillance
     Human arbovirus testing at the ADH Laboratory
     Equine testing - Arkansas Livestock and Poultry
      Commission Lab.
     Mosquito pool testing – collected by ADH
      Environmental Specialists & tested at Arkansas
      Livestock and Poultry Commission Lab.
     Dead bird surveillance - tested at Arkansas Livestock
      and Poultry Commission Lab.
AR Mosquito Surveillance, 2002
WNV Positive Mosquitoes, 2002
 AR Bird Surveillance, 2002
426 positives / 2116 samples from 58 Counties
2002 Positive Horses
   108 WNV, 27 EEE
Arkansas Human WNV Case Map
     as of October 23, 2002
What’s being done about WNV in AR?
   AR Governor authorized release of $1,000,000
    to County Judges to assist counties with
    mosquito abatement to control WNV.
     Required partnership with Cooperative Extension
      Service and Department of Health Environmental
      Specialists for technical assistance and advice
     Funds restricted for purchase of:

        Mosquito larvicides

        Hand/backpack equipment for larvicide

         application
        WNV education materials
What’s being done about WNV in AR?

   Univ. of AR, Cooperative Extension Service
    prepared Fact Sheets:
      FSA7059 – Mosquito Control Around the Home

       and in Communities
      FSA7060 – Developing a Community Mosquito

       Abatement Program
How Do You Protect Yourself From WNV?


The best way to prevent infections with West Nile virus
and other mosquito-borne diseases is to avoid getting
mosquito bites.




Aedes sp.                                     Anopheles sp.



                              Culex sp.
    Practical Risk Reduction Practices:
   Minimize time spent outdoors when mosquitoes are most active (usually
    dusk and dawn)
   If you go out when mosquitoes are active, cover up by wearing shoes,
    socks, long-sleeved shirts, and long pants
   Consider using a mosquito repellant containing DEET (N,N-diethylmethyl-
    meta-toluamide) on exposed skin. Carefully read and follow label
    directions
   Make sure your home has tight-fitting screens that keep mosquitoes out
   All mosquitoes need standing water for the first stages of development.
    Eliminate stagnant and standing water around your home by disposing of
    any discarded containers, tires, plant pots, etc. that can hold water.
   In the spring, inspect rain gutters and downspouts and remove any leaves
    and other debris.
   Stack wheelbarrows, tubs, buckets, barrels, boats or canoes, etc. upside
    down so that water does not accumulate in them.
   Empty bird baths, lily ponds, small wading pools, etc. at least once a
    week.
   Properly maintain backyard swimming pools. Cover any pool not in use
    so rainwater and leaves do not accumulate. Be sure the cover does not
    hold pockets of water.
Future of West Nile Virus?

   The continued expansion of West Nile
    virus in the United States indicates that it
    is permanently established in the Western
    Hemisphere.
QUESTIONS?
Other Encephalitis Diseases in AR
   Eastern Equine Encephalitis (EEE)
       humans, horses, pheasants, and emus very susceptible.
       only a few human cases of EEE ever reported in AR
       infected children most likely to have severe illness or die
       EEE considered the most severe arboviral encephalitis
       human fatality rate approaches 70%
       individuals who recover frequently have permanent,
        disabling side effects
       recent sporadic outbreaks in horses and emus in AR
       EEE symptoms in horses: walk in circles, unbalanced,
        head droops and convulsion
       Emus infected with EEE will have bloody diarrhea
       no vaccine for routine use in humans but one is available
        for horses and emus and can prevent EEE if vaccinated
        regularly.
Other Encephalitis Diseases in AR
   St. Louis Encephalitis (SLE)
      SLE does not cause disease in animals

      strictly a human disease

      Large outbreaks of SLE have sporadically occurred
       throughout the US
      symptoms typically milder, with most people experiencing
       flu like symptoms
      Elderly are ones that are primarily affected

      AR experiences sporadic cases of SLE, most going
       unreported
      1991 - largest recent outbreak in AR

          Pine Bluff - 28 hospitalized with five deaths all over the
           age of 60
      2 cases of SLE were reported from Pine Bluff in 2001 with
       one being fatal.
USA Bird Map
USA Human Map
USA Veterinary Map
USA Mosquito Map
USA Sentinel Flock Map
    Mosquito Control Suggestions for
    Around the Home
   Dispose of tin cans, plastic containers, ceramic pots or similar
    water-holding containers.
   Remove all discarded tires on your property.
   Drill holes in bottoms of recycling containers kept outdoors.
   Insure roof gutters drain properly and clean clogged gutters in the
    spring and fall.
   Turn over plastic wading pools and wheelbarrows when not in use.
   Change the water in bird baths.
   Clean vegetation and debris from the edges of ponds.
   Clean and chlorinate swimming pools, outdoor saunas and hot tubs.
   Drain water from pool covers.
   Use landscaping to eliminate stagnant water that collects on your
    property.
Historical Occurrence of Mosquito Borne Viruses in
AR, 2001
QUESTIONS?

				
DOCUMENT INFO