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Record mosquito numbers cause West Nile virus threat across Pennsylvania

Posted 8/8/18

Receding floodwaters and heavy rains across Pennsylvania are creating a perfect storm of conditions that have contributed to the highest level of West Nile virus activity in the mosquito population …

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Record mosquito numbers cause West Nile virus threat across Pennsylvania

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Receding floodwaters and heavy rains across Pennsylvania are creating a perfect storm of conditions that have contributed to the highest level of West Nile virus activity in the mosquito population since the disease was first introduced in 2000, according to the state Department of Environmental Protection.

The disease, which has infected more than 150 people in the past six years, is on track to pose an unusually higher-than-normal risk this year and is widespread throughout the commonwealth, having already been found in 51 Pennsylvania counties as of Aug. 1, including Dauphin.

“With record levels of West Nile virus activity in mosquitoes already found, we are at increased risk of disease from a bite of a mosquito. It is imperative that Pennsylvania residents take common-sense precautions to protect themselves from mosquitoes,” said DEP Secretary Patrick McDonnell. “There has been one human case already this year. Our goal is for that to be the only one. By eliminating places for mosquitoes to lay eggs, using insect repellent and other protective measures, and targeted use of pesticides, we can all make sure Pennsylvanians are protected.”

The Pennsylvania Department of Health has issued an advisory through the Health Advisory Network to alert medical professionals about the risk of West Nile virus. Gov. Tom Wolf and the Legislature recently approved a $140,000 increase to the program’s budget. DEP West Nile virus program staff have conducted multiple operations to reduce mosquito habitats from tire piles and other areas.

These efforts will be ongoing until the first hard frost of the year.

The virus can have devastating effects on bird populations as well. Pennsylvania’s state bird, the ruffed grouse, has been hit especially hard by the virus, and the winter hunting season for the bird has been curtailed as a result of the virus and habitat loss.

Residents can eliminate habitat by getting rid of standing and stagnant water where mosquitoes lay eggs.

“Mosquitoes are weak flyers and won’t travel far from where they are born. If there are mosquitoes in your backyard or neighborhood, they are likely laying eggs there as well,” said Matt Helwig, a biologist with the DEP mosquito program. “If you’re being bitten by mosquitoes, they are 9 times out of 10 coming from your property. Get rid of even small amounts of standing water around your home.”

Common places water can accumulate are outdoor features such as potted plants and birdbaths, yard debris, storage bins, kids’ toys (including kiddie pools), rain gutters, and even corrugated downspouts.

“It doesn’t take much for several hundred mosquitoes to be born. The small pool of water that collects in a single upturned bottle cap is an incubator for as many as 300 mosquito eggs,” Helwig said.

Mosquitoes acquire the virus by biting infected birds and transmit the virus to people through a subsequent bite. Use of commonly sold insect repellents, like those using DEET, Picaridin or other EPA-registered repellents, can cut down on mosquito bites, and possible exposure to the virus, according to the DEP. Long pants and sleeves are also an important way to cut down on possible exposure to mosquitoes.

DEP and county partners throughout the state will also conduct routine, localized spraying events to control infected adult populations of mosquitoes. These operations are conducted when and where deemed necessary based on recent population survey results.

“Control operations are a strong tool, but they are not a substitute for preventive measures like eliminating standing, stagnant water,” Helwig said.

Symptoms of West Nile virus in humans are typically like those of a mild flu, but the virus can lead to a more serious condition that includes swelling of the brain, muscle convulsions, coma, paralysis and death.

Since DEP first began monitoring for the virus in 2000, there have been 33 fatal cases of West Nile virus in Pennsylvania.

“While the symptoms may not seem threatening in the vast majority of cases, serious impacts to health can occur from being bitten by mosquitoes that carry this virus,” McDonnell said.

For more information, go to www.westnile.state.pa.us.

More WNV-infected samples collected in Dauphin County, bringing total to 62

The Dauphin County Conservation District has collected more West Nile virus-infected mosquito samples, bringing the total to 62 this year.  

Infected samples have been found in the city of Harrisburg, Conewago Township, East Hanover Township, Derry Township, Halifax Township, Lower Paxton Township, Londonderry Township, Lykens borough, Middle Paxton Township, Millersburg borough, Paxtang borough, Susquehanna Township, Swatara Township, Washington Township and West Hanover Township.

No human cases of West Nile virus have been reported this year in Dauphin County.

The county’s WNV Control Program is continuing to closely monitor conditions and implement control measures to reduce the mosquito population and prevent the virus from spreading, Dauphin County commissioners said last week.

Certain species of mosquitoes carry West Nile virus, which, when transmitted to people, can cause West Nile encephalitis, an infection that can result in an inflammation of the brain. According to the Centers for Disease Control and Prevention, all residents of areas where virus activity has been identified are at risk of getting West Nile encephalitis. 

The following precautions are recommended:

• Buy products with Bti (Bacillus thuringiensis israelensis) — a naturally occurring bacteria that kills mosquito larvae but is safe for people, pets and plants — for stagnant pools of water in the lawn and garden.

• Remove any standing water in pots, containers, pool covers, tires, wheelbarrows, wading pools, roof gutters and other containers that hold water.

• Make sure screens fit tightly over doors and windows to keep mosquitoes out of homes.

• Consider wearing long-sleeved shirts, long pants and socks when outdoors, particularly when mosquitoes are most active at dawn and dusk, or in areas known for having large numbers of mosquitoes.

• Reduce outdoor exposure at dawn and dusk during peak mosquito periods, usually April through October.

• Use insect repellents according to the manufacturer’s instructions. An effective repellent will contain DEET, picaridin or oil of lemon eucalyptus. Consult with a pediatrician or family physician if you have questions about the use of repellent on children, as repellent is not recommended for children younger than 2 months.

To learn more about WNV and prevention, visit the CDC’s website at www.cdc.gov/westnile.  For more information about Dauphin County’s WNV Control Program, contact Christopher Hooper, program coordinator, at 717-921-8100.