Deluge likely to boost mosquitoes

Splashing along as he explored the swollen Concord River in Bedford last week, David Henley quickly found his prey: mosquito larvae.

It was hard to miss, said Henley, superintendent of the East Middlesex Mosquito Control Project. Thanks to recent flooding, people will not have to search hard for mosquitoes in a week or two.

They'll find you.

``There will certainly be consequences down the road," Henley said. ``There's a massive amount of water out there."

Though cases are rare, the threat of mosquito-borne illnesses such as Eastern e quine e ncep halitis and West Nile v irus means that thinning the mosquito population is increasingly a health measure, not simply warfare against a buzzing pest.

In some communities that are still bailing out from this month's floods, the forecast for a bumper crop of mosquitoes is yet another bad result spawned by the deluge.

And some towns, such as North Andover, are without the means to fight off the pests.

Last year, North Andover declined to renew its membership in the Northeast Massachusetts Mosquito Control and Wetlands Management District. At their annual T own M eeting June 5, voters will consider rejoining the district at a cost of $86,124 a year. The Board of Health proposed it.

Without the state-regional mosquito control, there are few contractors in Massachusetts for hire, said Susan Sawyer, director of the North Andover Health Department.

Though well aware of the potential for a larger population of mosquitoes this year, Sawyer said she has heard little debate about mosquitoes in town so far.

``We're still in the rescue and cleanup mode at this time," she said of North Andover's flood damage.

Walter Montgomery, Henley's counterpart with the Northeast Massachusetts Mosquito Control and Wetlands Management District, said flood waters washed away a considerable amount of larvae in Essex County. But Middlesex does not appear to be as lucky, Henley said.

The Middlesex district generally received less rainfall than the Northeast district, Henley noted. Montgomery agreed.

``The key factor is we had 14-plus inches of rain," said Montgomery, in a telephone interview from his Newburyport office.

While some larvae get washed away with every large storm, the Middlesex control project continues to find a lot of larvae in wetlands and along rivers, said Henley. One of Henley's coworkers discovered a great deal of larvae Monday on the Ipswich and Saugus rivers.

``There's still a lot of larvae out there," Henley said. ``I think they'll see a lot of mosquitoes."

North Andover should expect a large mosquito population, given the larvae found on the Ipswich River in nearby North Reading, according to Henley.

Montgomery's office has not surveyed the North Andover area yet. Though he does not expect a large crop of spring-brood mosquitoes in the Northeast district, he said there could be specific sites or pockets in which mosquitoes are more of a nuisance than in the past.

The East Middlesex Mosquito Control Project, which is based in Waltham, only sprays nine of the 25 towns in its area because some of the urban communities have not reported large populations of adult mosquitoes in the past, Henley said. Some towns hire private contractors for spraying as needed.

The project gets funding and direction from municipalities. Its 2006 budget is about $550,000. Services include spraying of some wetlands, neighborhoods, and storm drains, as well as capturing mosquitoes in traps, luring them in with dry ice, which emits carbon dioxide.

Henley said the nine towns receiving spraying, as of this spring, were Bedford, Burlington, Framingham, North Reading, Reading, Sudbury, Wakefield, Waltham, and Weston.

Per U S Wildlife Service regulation, the project does not spray in the Great Meadows National Wildlife Refuge, the swath of freshwater wetlands along the Concord and Sudbury rivers.

Henley said he oversaw a helicopter application of low-toxicity pesticides in mid-April, but he does not have plans for another aerial spraying. If the threat of disease picks up later in the summer, he said additional spraying could be conducted at that time.

Cases of Eastern e quine e ncephalitis and West Nile v irus in Massachusetts and New Hampshire have prompted officials in both states to encourage residents to take certain measures, such as eliminating standing water and wearing insect repellent.

``We need to take preventative steps," said John Stephen, commissioner of the New Hampshire Department of Health and Human Services. ``We know triple E is here."

Stephen issued an alert last week for the public to avoid flood water that may be contaminated or have unhealthy levels of bacteria. In the weeks ahead, he warns, residents should be prepared to combat a larger mosquito population. He said there are reasonable steps to take, like wearing long-sleeve d shirts, mending holes in window screens, and staying indoors when possible after nightfall.

``We do not want the public to panic," said Stephen.

Public concern has led to additional spraying contracts. Mike Morrison, the president of Municipal Pest Management Services, recently landed a new spraying assignment in York, Maine. His company sprays in more than two dozen towns in southern New Hampshire, including Windham.

Morrison, a longtime entomologist, said this May stands to be one of the wettest Mays on record. And thus, with the expanded breeding territory, he said this year's mosquito population could be the worst in decades. He said the region will have a better sense of the population in another two weeks.

``We're not at a crisis right now," he said.

While Henley was surprised at the size of the latest mosquito larvae, he said there are no signs to indicate this year will be worse than last year for threat of mosquito-borne diseases. He said the chance of getting such a disease in Massachusetts is extremely small .

The U S Centers for Disease Control's monitoring of West Nile Virus activity in 2005 lists six cases in Massachusetts, one of which was a fatality. By November of 2005, the state Department of Public Health had tracked four human cases of EEE and confirmed EEE virus infections in four horses, including one from Concord.

According to the CDC, both viruses are transmitted to humans through the bites of infected mosquitoes. Eastern e quine e ncephalitis symptoms include flu-like illness with a fever, headache, sore throat, and coma. In severe cases, death can result. Symptoms appear in three to 10 days. West Nile v irus symptoms include headache, body aches, tremors, loss of vision, and paralysis. Its incubation period is two to 15 days. The CDC estimates that 80 percent of people infected with West Nile v irus do not develop any symptoms.

Tests on captured mosquitoes last year found a greater number infected. The Massachusetts Department of Public Health reported 99 mosquito samples tested positive for West Nile v irus and 45 mosquito samples tested positive for EEE. That is about three times the number of mosquitoes testing positive in 2004.

Twenty-four of the positive results came from Middlesex County, including the Culex pipiens species testing positive for West Nile v irus in Belmont, Lexington, Waltham, Weston, and Wilmington.

There are nine mosquito control districts covering 186 communities in Massachusetts, each district created by the Legislature and run under the umbrella of the s tate Reclamation and Mosquito Control Board. A town must join for at least three years.

There are 50 mosquito species commonly found in Massachusetts, according to the East Middlesex Mosquito Control Project.