Malarial Mosquitoes Found in US Near Pair of Infections

October 3, 2002
By Michael Laris
The Washington Post

Washington - Health authorities say they have discovered malaria-carrying mosquitoes in two neighborhoods in the state of Virginia's Loudoun county, several kilometers from where two teen-agers became ill with the disease in a rare outbreak recently.

The finding marks the first time in at least 20 years that mosquitoes carrying the parasite have been identified in a US community where humans were also infected with malaria, according to Richard Steketee, chief of the malaria epidemiology branch of the US Centers for Disease Control and Prevention.

Federal and state authorities said they will do more tests on the Loudoun insects to confirm the results.
"Having two cases of domestically transmitted malaria, and finding two pools of positive mosquitoes, hasn't happened for decades in the US," said David Goodfriend, director of Loudoun's health department.

Officials in the state of Maryland, about a kilometer from one of the infected mosquito pools in Loudoun, have arranged for a military team of malaria experts to help eradicate other infected mosquitoes, according to Lynn Frank, chief of public health 
services in Maryland's Montgomery county.

Frank said that when Goodfriend called her with Loudoun's news, she "stopped everything I was working on" to jump into the effort. "It has become our number one priority right now," she said. For the first time, officials will test mosquitoes trapped in Montgomery for malaria, she said.

Health officials emphasized that the strain of malaria-causing parasite found this week in mosquitoes near the Potomac River triggers a highly unpleasant, but comparatively mild, form of malaria that can be easily treated not the strain that kills millions of people in the developing world.

Still, local and federal health officials said the findings have prompted additional anti-malaria measures, including more larvicide application in areas where mosquitoes breed and new traps. Additional adult mosquito spraying is also under consideration.
Nature also could offer help in the battle, authorities said. As the weather in the area gets cooler, fewer people spend long periods of time outside, and the onset of the cold season should also kill off many mosquitoes.

Goodfriend said the malarial mosquitoes found last week probably were different from the ones that infected the teen-agers, since the anopheline mosquitoes that transmit the disease usually don't fly more than about a kilometer. Officials also believe that someone other than the two teen-agers already identified was the source of the parasites in the mosquitoes discovered last week. But no other human cases of malaria have come to light.

Officials said they will use a series of sophisticated tools to try to solve an extraordinary medical mystery that could have widespread public health implications.

"There is malaria out there, and we have to pay attention to it," the CDC's Steketee said. "It's rare, but it's not a non-problem."