State increases its mosquito-control program

The Baltimore Sun

The Maryland Department of Agriculture is boosting its mosquito control efforts in the wake of what health officials fear could be the first human case of West Nile virus in the state this year.

Agriculture officials have more than doubled mosquito trapping on the Lower Eastern Shore, said Cy Lesser, the department's chief of mosquito control.

The move came after the state Department of Health and Mental Hygiene reported last week what they suspect is a human case of the virus. Officials decline to say much about the case except that it involves a resident of Worcester County.

"The report has not been confirmed," said Karen Black, Health Department spokeswoman. "That will take a couple of weeks."

For most of the year, the mosquito population had been well below normal because of the drought, Lesser said. But that changed a few weeks ago when a combination of rains and a new moon increased tidal flooding of several hundred thousand acres of Eastern Shore marshland.

The water revived the mosquito eggs that had lain scattered on the marshland mud for weeks, and they rapidly developed into adult mosquitoes. The earlier drought had eliminated the minnows that would normally feed on the mosquito larvae.

"There were no predators around to control the mosquito population," he said.

And the worst lies ahead - September is traditionally marked by heavy mosquito activity, Lesser said.

"There is increased potential of mosquitoes carrying the virus," he said. "We don't think people need to be unduly concerned, but they should take some efforts to reduce the threat."

Mosquito control is the key tool in the effort to ameliorate the risk of infection with all mosquito-borne diseases, said Maryland Agriculture Secretary Roger L. Richardson.

The department is intensifying efforts with additional surveillance and more aggressive control activities in the Lower Eastern Shore for the remainder to the mosquito season. Steps include an increase in flights of its twin-engine Beechcraft King airplane used to spray mosquito-killing chemicals.

More than 50,000 acres were sprayed last week, and more spraying will take place this week, Lesser said.

The department also is using trucks to spray areas that could be reached from the road, and field workers have been meeting with residents to suggest ways to rid their yards of containers holding water and other mosquito breeding nests.

Since 2001, there have been 136 cases of West Nile virus in Maryland and 18 deaths, health officials said. Six cases were reported last year, one more than in 2005. The disease peaked here in 2003 when 73 cases resulted in eight fatalities.

Health Department officials said most mosquitoes do not pose a threat to public health because they are not infected with viruses or other pathogens. Less then 1 percent of the people bitten by a mosquito carrying the West Nile virus will become ill.

People most at risk for developing symptoms of the disease are those older than 50 and those with compromised immune systems. The most common symptoms are fever, headaches, weakness, and joint and muscle pain.

The state agencies suggest several steps that residents can take to protect themselves:

Avoid unnecessary outdoor activities at dawn and dusk when mosquitoes are most active.

Wear light clothing, long pants, long-sleeved shirts and hats when outdoors.

Use mosquito repellents. The Department of Agriculture says that those containing DEET or Picaridin work better and last longer.

Remove standing water from flower pots, tarps, receptacles and other containers. There is no vaccine against the West Nile virus for humans.

Vaccines are available for horses and some other farm animals. More than 230 horses were infected with the virus in 2003. None was reported last year.

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