West Nile Virus Update

1
West Nile Virus Update

• John D. Hopkins, Ph.D.
• Extension Urban Entomologist

2
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.

3
Geographic Distribution of the Japanese
Encephalitis Serocomplex (Family Flaviridae), 2000
4
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.

5
West Nile Virus Transmission Cycle
6
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 (gt 50 yrs
  old)
• high fever, severe headache, nausea, stiff neck,
  confusion, muscle weakness, paralysis,
  disorientation, convulsions, coma, and rarely,
  death.
• lt 1 of humans infected with WNV will develop
  serious illness.

7
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.
8
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.

9
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

10
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.

11
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)

12
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

13
History of West Nile Virus (continued)

• Sept. 2001
• 4 blue jays with WNV (Union, Saline, and
  Sebastian Cos in AR)
• No human WNV cases yet diagnosed in AR

14
History of West Nile Virus (continued)

• October 2001
• WNV present in 27 states and Canada

15
WNV-Positive Dead Birds, 2001
7,338 birds 328 counties 27 states DC
DC
As of 3/13/2002
16
History of West Nile Virus (continued)

• 2001 - human infection with WNV
• 10 states
• 66 cases
• 9 deaths.

17
Human WNV Disease Cases, 2001
66 cases 39 counties 10 states
As of 3/13/2002
18
History of West Nile Virus (continued)

• 2002 WNV activity spread to most states

19
History of West Nile Virus (continued)

• 2002 3242 human cases 176 deaths

20
Whats 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.

21
AR Mosquito Surveillance, 2002
22
WNV Positive Mosquitoes, 2002
23
AR Bird Surveillance, 2002 426 positives / 2116
samples from 58 Counties
24
2002 Positive Horses108 WNV, 27 EEE
25
Arkansas Human WNV Case Map as of October 23, 2002
26
Whats 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

27
Whats 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

28
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.
29
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.

30
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.

31
QUESTIONS?
32
(No Transcript)
33
(No Transcript)
34
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.

35
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.

36
(No Transcript)
37
(No Transcript)
38
USA Bird Map
39
USA Human Map
40
USA Veterinary Map
41
USA Mosquito Map
42
USA Sentinel Flock Map
43
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.

44
Historical Occurrence of Mosquito Borne Viruses
in AR, 2001
45
QUESTIONS?
46
(No Transcript)
47
(No Transcript)
48
(No Transcript)