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Vector-borne Diseases in Lucas County
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Vector-borne Diseases in Lucas County
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West Nile Virus (WNV)
Human Case Update (2002) (2003)
WNV is primarily a bird-mosquito disease that accidentally infects humans and other mammals, such as horses. Depending on how the virus survives the winter, the transmission cycle begins in the spring when an infected bird is fed upon by a mosquito or an infected mosquito feeds upon a bird. The cycle between birds and mosquitoes continues throughout spring and summer, increasing the prevalence of the virus in the wild. Eventually, during late summer or early fall, the amount of virus in the wild is so great that accidental infections begin to occur in humans and other mammals. Infected humans and other mammals are believed to be incapable of spreading the virus any further. New cases may continue to be seen until the weather cools and the mosquito season ends.
Transmission Cycle
It is not known exactly how the virus survives the winter and re-emerges in the wild the following spring. The two most common ideas are that the virus survives in infected mosquitoes that live through the winter as adults or the virus survives through migrating bird and mosquito populations, returning to the original area in an infected bird.
Symptoms:
The condition known as “West Nile Fever” is caused by a virus known as the West Nile Virus (WNV). The symptoms of a WNV infection begin to occur in humans approximately 3-15 days after being bitten by an infected mosquito. Most human infections of WNV are asymptomatic or result in mild non-descriptive symptoms. These non-descript symptoms are similar to the common flu: fever, headache, nausea, vomiting, and skin rashes. Symptoms of severe WNV infections are confusion, muscle weakness, decreased reflexes, respiratory difficulties, tremors, convulsions, paralysis, and even death.
History:
WNV was first discovered in a woman from Uganda in 1937. Since its first discovery, WNV has been responsible for numerous epidemics throughout Africa, the Middle East, and Europe. The earliest documented epidemics of WNV occurred in Israel. In a 1950 epidemic, over 500 people were hospitalized from WNV. Subsequent epidemics in Israel occurred in 1951-1954 and 1957. During one of these later epidemics 636 cases of clinical WNV were treated in a military camp of only 1,000 people. The most recent epidemic in Israel occurred in the fall of 2000. During this outbreak, approximately 180 clinical cases were diagnosed with 13 deaths. The largest epidemic of WNV, to date, occurred in South Africa in 1974. During this epidemic, hundreds of clinical cases were treated and 18,000 WNV infections were estimated to have occurred in a single town with a population of 30,000 people.
Though extremely widespread throughout other portions of the world (2002 Distribution of WNV in the US), WNV didn’t emerge in the Western hemisphere until the summer of 1999 in New York City. The New York City epidemic resulted in 62 clinical cases of WNV, including seven deaths. Since its emergence in the United States, WNV has spread quickly. By the end of the year 2001, WNV was detected in 27 states and the District of Columbia.
Prevention:
The elimination of WNV as a threat to humans is improbable because of its global distribution and efficient survival strategies. The most practical approach to preventing human cases involves the reduction of local mosquito populations. Mosquitoes are an extremely successful group of insects that are prolific reproducers. The completion of the lifecycle of a mosquito requires the presence of standing water. Below is a list of things that can be done to protect yourself from mosquitoes and help prevent the further spread of WNV.
YOUR YARD: Eliminate Standing Water
- Empty water from scrap tires and store them in a protected location.
- Empty water holding containers (i.e. planters, jars, bottles, pool covers, drums, etc.) and store them overturned or in a protected location.
- Empty bird baths, wading pools, and boats every 2-3 days when not in use, or overturn them.
- Clean your gutters to prevent clogging and water accumulation.
- Ensure ornamental ponds have aerators or that they are stocked with mosquito-fish. These fish are provided free of charge to all Lucas County residents, upon request, from the Toledo Area Sanitary District
YOUR HOME: Keep Mosquitoes Out
- Windows should have screens that are tight fitting and free of holes.
- Doors should have tight seals that do not leave any openings to the outside.
YOURSELF: Stay Alert
- Wear light colored clothing (long sleeves and pants when possible) when outdoors during active mosquito times and in infested areas.
- Use mosquito netting if you sleep outdoors or in an unscreened structure.
- Avoid physical exertion, sweat attracts mosquitoes.
- Avoid wearing excess amounts of perfume and cologne that can also attract mosquitoes.
- Lower outdoor alcohol consumption, alcohol has been linked to increased mosquito feeding.
- Use mosquito repellent, per the directions listed on the container.
Local Control Efforts:
The Toledo-Lucas County Health Department investigates complaints regarding mosquito harborages, participates in surveillance efforts, investigates cases of WNV in human populations, and provides education about the virus. You can contact the Toledo-Lucas County Health Department at (419) 213-4100, Ext. #3 for additional information about WNV.
Because American crows and blue jays are extremely susceptible to the WNV they are a good indicator of the presence of WNV in the community.
If you see a dead bird you can double bag it using plastic grocery sacks and place it in the garbage. Wear gloves when you place the bird in the bag and be sure to wash your hands after touching any wildlife, whether living or dead.
More Information:
For more information about West Nile Virus contact the Toledo-Lucas County Health Department at (419) 213-4100 #3 or print out a copy of our informational brochure (link to Adobe online version of WNV TLCHD brochure). Listed below are several other websites that can provide additional information.
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