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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?
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