- The Washington Times - Saturday, June 12, 2004

ANNAPOLIS — Maryland mosquitoes, which bred en masse last year after a wet spring, should be slightly less populous this year, state entomologists say. However, the little suckers are carrying a weapon they didn’t brandish until well into mosquito season last year — the West Nile virus.

For the first time, state agriculture officials and scientists know at the start of the season that they are waging a war against a brood that is infected. No mosquitoes have tested positive for West Nile, but state agriculture and health officials know the virus is established because it was widespread at the close of the 2003 mosquito season in October.

“Once it becomes established in a geographic area, it remains there from year to year,” said Cy Lesser, chief of mosquito control for the state Department of Agriculture.

Officials are particularly concerned about the Eastern Shore and southern Maryland, where they estimate one in 1,000 mosquitoes will carry West Nile. Those are especially “hot” areas for the biting bugs because of low-lying marshes and coastlines, Mr. Lesser said.

“We consider the mosquito population as more than just a pest. We consider them as vectors that can possibly carry West Nile,” Mr. Lesser said.

Statewide, Department of Agriculture workers are laying traps — equipped with light bulbs and dry ice as bait — to lure the insects for a population count and virus testing.

However, this year, fewer mosquitoes will trigger insecticide spraying, Mr. Lesser said.

Instead of 20 mosquitoes a night in an unbaited light trap, Mr. Lesser said 10 is now enough to merit spraying. The “landing rate” test, which counts how many mosquitoes land on a person in a minute, gets the agency’s attention at one bug a minute — instead of five in two minutes.

Agricultural officials have been spraying larvicides and bacterial insecticides from ground trucks and hand sprayers since March.

West Nile first appeared in the Western Hemisphere in 1999, when it showed up in New York state. Since then, it has spread across the United States, with Oregon and Washington the only continental states free of the virus.

The 9,006 cases reported last year were more than double the 4,156 cases in 2002. In Maryland, 73 cases were confirmed in 2003. Eight people died in the state.

The Maryland mosquito most likely to carry West Nile is Culex salinarius, known as aggressive biters.

“We consider them our primary problem,” Mr. Lesser said. “There are a wide range of animals they feed on — people, pets, livestock and birds.”

West Nile is carried by birds and transmitted by mosquitoes to other birds, horses and people.

“Particularly in the rural parts of state, most of people there are very used to mosquitoes, and they consider them a nuisance. This year, we hope they’ll realize they can transmit disease and they’ll take adequate precautions,” Mr. Lesser said

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