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Source: Newsday

West Nile concern has Nassau, Suffolk spraying sooner

BY JENNIFER SMITH

Posted: August 9, 2010
Originally Published: August 8, 2010

Alarmed by unusually early and numerous detections of West Nile virus, Nassau and Suffolk counties are spraying pesticides in Long Island neighborhoods sooner - and more often - than in past years.

"We're trying to get ahead of it, so we don't find ourselves in the position where we have 20 human cases and the [mosquito] population is rising," said Bryan Matthews, West Nile virus coordinator for the Nassau County health department.

The sprayings are targeting adult mosquitoes with chemicals called pyrethroids, which kill a range of insects. More toxic than treatments mosquito control programs use to limit the larvae, these adulticides are being sprayed in areas where mosquitoes carrying West Nile have been found in hopes of containing the potentially fatal virus.

On Long Island, 11 people have died from the 116 human cases of West Nile virus reported since the disease first emerged in 1999, according to the New York State Health Department.

Regular spraying in Suffolk

Suffolk's mosquito program regularly sprays adulticides to combat West Nile virus and to reduce the number of "nuisance" mosquitoes on Fire Island and in the Mastics. Nassau has largely avoided use of the chemicals.

This year is different, officials said. Last week, Nassau sent out spray trucks.

As of last week, there were 125 infected mosquito pools on Long Island - the most at this point in the season since West Nile was first reported in New York. The state has issued a public health threat declaration for Nassau, and suspected human West Nile virus cases in Nassau, Suffolk and New York City are awaiting confirmation by state health officials.

"The feeling was we had better do some prophylactic spraying - both adulticides and larvicides as needed and as appropriate," said Suffolk health Commissioner Dr. James Tomarken.

A high number of positive mosquito pools mean potentially more human cases, said entomologist Harry Savage of the federal Centers for Disease Control.

But the cycle of the disease complicates such predictions. West Nile virus is harbored by birds and spread to humans by mosquitoes that have fed on infected birds. People can reduce exposure to infected mosquitoes with repellent and protective clothing, while the insects might dine on more birds instead of people, Savage said.

Still, the greater the proportion of local mosquitoes that carry the virus, the more nearby humans risk contracting the disease, officials said.

Positive results

In Nassau, 49 of the 266 mosquito pools submitted for testing came back positive - about 18.4 percent, compared with 8 percent of the 900 samples tested in Suffolk County.

That may explain why Nassau has taken a more aggressive approach this year. The county sprayed adulticides in 1999, the first year it appeared, but did only isolated applications in 2000 and 2005 until a wave of human cases in 2008 triggered another public health threat declaration.

"Our hope is to not have to do extensive spraying," said Nassau health Commissioner Dr. Maria Torella Carney.

She said the county decided to spray adulticides now because data from past years indicated when more than six infected mosquito pools are detected in a week, human cases tend to follow. Nassau officials said the pesticides are applied to far fewer acres than during the emergency aerial spraying in 2008. Still, officials have not ruled out aerial spraying this year as needed to target areas less accessible by truck.

Concern about the infected pools had Suffolk's pesticide trucks out in neighborhoods on July 8, six weeks earlier than last year and 10 days sooner than in 2008. Aerial spraying began on July 22, about a month earlier than usual, officials said.

High response level

"This is the highest level of response for this time of year, ever," Suffolk spokeswoman Grace Kelly-McGovern said in an e-mail.

Studies show the chemicals that attack adult mosquitoes can cause adverse health effects in humans, but in doses far higher than those used to kill insects. Health officials caution that pregnant women and children avoid exposure when possible and advise residents to shut windows and take pet food dishes indoors during spraying.

Adrienne Esposito, of Citizens Campaign for the Environment, criticized Suffolk for spraying adulticides to control nuisance mosquitoes, but said she thought Nassau's use of adulticides this year was appropriate. "We believe they are following the state protocol, which is limited, targeted spraying when active virus is found," she said.


Q&A

What is West Nile virus?

West Nile virus is believed to have first appeared in the United States in 1999. It falls into the family of viruses that cause yellow fever and dengue fever. The virus can infect humans, birds, horses and some other animals, and is spread mostly through mosquito bites. People usually start to show symptoms of the virus from three to 14 days after being infected.

What are the symptoms?

About 80 percent of people who contract West Nile will feel no symptoms. Others can develop West Nile fever, which causes body aches, nausea and vomiting, lasting from a few days to several weeks.

About one in every 150 people infected suffer the virus' most severe symptoms: a high fever, disorientation, tremors, muscle weakness and paralysis. These symptoms can last several weeks and cause irreversible neurological damage.

How do you avoid contracting it?

Avoid mosquito bites by wearing insect repellent, checking door and window screens for holes, and emptying standing water - which can become breeding spots for mosquitoes - in flower pots and pools.

SOURCE: CENTERS FOR DISEASE CONTROL; NATIONAL INSTITUTES OF HEALTH