The Board of Supervisors has authorized $350,000 to eradicate mosquitoes to help control West Nile virus and malaria, down from $400,000 last year. But David Goodfriend, director of the Loudoun County Health Department, said his staff can do the job better and more cheaply by contracting out less work and learning from experience.

Goodfriend said the health department will start testing birds for West Nile in just over a week, on April 1, because some mosquitoes might have survived the winter and some birds might have arrived in Loudoun from warmer climates where mosquitoes live year-round.

He said health workers are already doing limited mosquito surveillance for malaria -- counting mosquito populations, determining what species are present in this area and testing whether they are carrying the disease. Surveillance for West Nile isn't scheduled to start until June unless birds start testing positive for the disease or horses or people contract it.

Malaria-carrying mosquitoes were discovered in two Loudoun neighborhoods last year, after two teenagers contracted the disease over the summer. It was the first time in decades that mosquitoes testing positive for malaria were found in the United States near where humans were infected.

Two Loudoun residents contracted the West Nile virus last year, one of whom died. Two Loudoun horses were among the record 42 horses who tested positive for the disease in Virginia, although both survived.

Goodfriend said that given how far and quickly West Nile has spread since it arrived in the United States in 1999, "our expectation is . . . we're likely to have a significant problem with West Nile throughout the Washington area" this year.

"Each year it's been progressing," he said. "Our expectation is that it will happen again."

Goodfriend said about half the $350,000 would be spent on larvicide, eradicating mosquitoes before they are old enough to bite, which he said was the best way to reduce the mosquito population. Last year, only one night of spraying of adult mosquitoes was authorized, in the Sugarland Run and Cascades subdivisions in eastern Loudoun after the malaria outbreak.

"This year we assume we'll be doing more spraying for West Nile, but that will all be driven by what our mosquito surveillance shows," Goodfriend said.

Goodfriend said that although county health workers would continue to investigate complaints of standing water where mosquitoes like to breed and to pick up and test dead birds for West Nile, some have also been trained to apply larvicide during those house calls. Previously, they referred the work to Clarke Environmental Mosquito Control, a private company in Fairfax County.

"Not only will it be much cheaper for the county for us to do that, it will also be better service for residents because we get to take care of the concern right on the spot," Goodfriend said.

He said that Clarke would continue to be contracted to trap mosquitoes in Loudoun because the county does not have an entomologist to determine which species are present. "We're hoping to learn from last year to do it more effectively, to put traps where they're really going to give us good information," Goodfriend said.

The county will start testing birds, top left, for West Nile on April 1. Limited surveillance of mosquitoes, above left and right, for malaria has already begun, and testing for West Nile is expected to start in June. Last year, Allison Hills looked for mosquito larva at Algonkian Park.