West Nile Virus Update : West Nile Virus Update John D. Hopkins, Ph.D.
Extension Urban Entomologist
What is West Nile Virus? : 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.
Slide3 : Geographic Distribution of the Japanese Encephalitis
Serocomplex (Family Flaviridae), 2000
West Nile Virus : 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.
Slide5 : West Nile Virus Transmission Cycle
Symptoms: WN fever / encephalitis : 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 : WNV Transmission Risk 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. Late Summer
Early Fall Late Summer
Early Fall Year Round
Treatment: WN fever / encephalitis : 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 : 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 : 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? : 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) : 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) : 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) : History of West Nile Virus (continued) October 2001:
WNV present in 27 states and Canada
WNV-Positive Dead Birds, 2001* : WNV-Positive Dead Birds, 2001* * As of 3/13/2002 DC 7,338 birds
328 counties
27 states & DC
History of West Nile Virus (continued) : History of West Nile Virus (continued) 2001 - human infection with WNV:
10 states
66 cases
9 deaths.
Human WNV Disease Cases, 2001* : Human WNV Disease Cases, 2001* * As of 3/13/2002 66 cases
39 counties
10 states
History of West Nile Virus (continued) : History of West Nile Virus (continued) 2002: WNV activity spread to most states
History of West Nile Virus (continued) : History of West Nile Virus (continued) 2002: 3242 human cases 176 deaths
What’s being done about WNV in AR? : 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 : AR Mosquito Surveillance, 2002
WNV Positive Mosquitoes, 2002 : WNV Positive Mosquitoes, 2002
AR Bird Surveillance, 2002 426 positives / 2116 samples from 58 Counties : AR Bird Surveillance, 2002 426 positives / 2116 samples from 58 Counties
2002 Positive Horses 108 WNV, 27 EEE : 2002 Positive Horses 108 WNV, 27 EEE
Slide25 : Arkansas Human WNV Case Map
as of October 23, 2002
What’s being done about WNV in AR? : 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? : 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? : 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.
Practical Risk Reduction Practices: : 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? : 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.
Slide31 : QUESTIONS?
Other Encephalitis Diseases in AR : 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 : 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.
Slide38 : USA Bird Map
Slide39 : USA Human Map
Slide40 : USA Veterinary Map
Slide41 : USA Mosquito Map
Slide42 : USA Sentinel Flock Map
Mosquito Control Suggestions for Around the Home : 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.
Slide44 : Historical Occurrence of Mosquito Borne Viruses in AR, 2001
Slide45 : QUESTIONS?