Dealing with West Nile virus more than just a nuisance
These northern house mosquitoes, the type known to carry West Nile virus, were trapped and will be tested for the virus.
A field crew with the state Department of Environmental Protection sprays pesticide on an area of standing water in order to prevent a mosquito infestation.
A mosquito bite was merely a nuisance for North Americans prior to 1999.
That summer, an African mosquito-borne disease, which had been in relative hibernation since its discovery in the 1930s, emerged with a vengeance in New York state, causing 62 cases of encephalitis and seven deaths.
The country was frenzied, and West Nile virus became a household name, eventually earning itself environmental protection specialists across the country.
Specialists like Ed Farrell.
Farrell, whose title is the uber-specific West Nile virus coordinator for the state Department of Environmental Protection, is working on his third year of monitoring and controlling the mosquito population in Washington County, among others, with the help of his field staff.
According to Farrell, West Nile season has yet to peak.
“Last year (the season) started really early,” said Farrell. “By this time last year, we had over 600 positive mosquito samples throughout the state, and this year we’ve only had two.”
That’s two positive mosquito samples and zero cases in birds or humans.
The West Nile field teams are required to set 15 mosquito traps per week in each county. Traps either tempt mosquitoes with carbon dioxide – the gas given off by animals as the result of metabolism and exhalation – or by mimicking an area where female mosquitoes might like to lay their eggs.
The trapped mosquitoes are then sent to a lab in Harrisburg to be tested for the West Nile virus.
“The field staff does the surveillance and control,” said Farrell. “They set the traps, dip for larvae and do control work like using truck-mounted low-volume sprayers, if necessary.”
The sprayers distribute pyrethroids, chemicals that kill insects including mosquitoes, and are considered an important tool to prevent the spread of West Nile virus. Fortunately, the chemicals are used only in areas in which West Nile-positive mosquitoes or animals were found.
The best tip if spraying is done in your area? Keep your family indoors during the spraying and for 30 minutes after to reduce your exposure.
Dipping for larvae refers to taking samples from standing water – where female mosquitoes lay their eggs – to check for the earliest stage of mosquito development, for those not familiar with water biology lingo.
Speaking of which, limiting sources of standing water is the most important thing private citizens can do to limit the mosquito population around their own home.
Need motivation to do a little yard maintenance?
“The best thing people can do is empty water holding devices in their yards,” said Farrell. “Tin cans, plastic containers, old pots, tires are a big problem … even roof gutters can produce millions of mosquitoes.”
Not all standing water is created equal, however. The species which carries West Nile virus, the northern house mosquito, is especially drawn to wet areas with a high organic composition. Areas with decaying vegetation, like compost bins, mulch piles and gutters, or with other forms of decaying organic matter, such as sewage treatment plants, are especially attractive to female northern house mosquitos.
While periods of excessive rain like Western Pennsylvania experienced during the month of July can certainly lead to a boom in the mosquito population, luckily, it encourages non-West Nile carrying varieties.
No human cases of West Nile virus have been detected in Washington County since 2008, and there have been no human cases in Pennsylvania in 2013 so far. The numbers may be misleading, however, since it is only 20 to 40 percent of those infected with West Nile virus who actually experience symptoms.
According to the Centers for Disease Control’s website, about 20 percent of those infected will develop a fever with other symptoms such as headache, body aches, joint aches, vomiting, diarrhea or rash, causing some to experience fatigue and weakness for weeks or months after the initial infection.
Less than 1 percent of those infected will develop a serious neurological illness (encephalitis or meningitis) which can cause neck stiffness, disorientation, seizures, paralysis and, in 10 percent of those who develop this neurological infection, death.
Treatment is supportive, meaning there is no specific treatment to cure the infection – a detail which surely causes a great deal of fear over becoming infected.
For now, area residents can hope for another season free from human infection and rely on the efforts of Ed Farrell and his team. More information can be found at www.westnile.state.pa.us.