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'Bio-bugs' could thwart disease

BY SUSAN KIM | BALTIMORE | February 16, 2001

Scientists are creating better bugs that could fight disaster-induced diseases that kill millions of people.

Cases of malaria tend to skyrocket after a major flood and "eradication of malaria-carrying mosquitoes has been very difficult," said David

O'Brochta, a biologist at the University of Maryland Biotechnology Institute. "The use of pesticides has become very limited. Insects are

becoming resistant. So we are trying to find a way to make mosquitoes incapable of harboring malaria parasites."

After flooding, pooling of water can lead to a rapid increase in the mosquito population, agreed Dr. Ravi Durvasula, a Yale researcher working with bio-engineered insects.

Across the country, university and government scientists -- funded by a few federal agencies, foundations, and farm groups -- are researching ways to combat such pests of human health.

Bio-bugs could also ward off crop disasters. California is trying to keep the cotton crop-destroying pink bollworm from establishing itself in the state's cotton-rich San Joaquin Valley. Every morning, five million sterile male moths are packed into canisters at the U.S. Department of Agriculture's (USDA) Animal and Plant Health Inspection laboratory in Phoenix, AZ and flown to Bakersfield, CA. They are dropped from the air wherever a stray pink bollworm has been detected in one of thousands of traps. The many sterile moths keep fewer fertile couples from finding each other.

These bugs aren't genetically modified, just sterilized, and they won't keep the pink bollworm away forever. And the genetically modified cotton plants that farmers are starting to raise do make a natural insecticide inside the boll, but some farmers still lose part of their crop to the insect.

Better eradication could come through genetic modification. Scientists are working to engineer a male moth that can pass a fatal flaw on to

any egg it fertilizes. Then they'll fly over cotton country and drop millions of these modified moths -- enough to beat out wild males in their quest for mates. That means a lot fewer boll worm babies and "a new tool in the farmer's arsenal," said Tom Miller, an entomologist at

University of California-Riverside.

Or imagine a mosquito bite that's actually beneficial to human health. Researchers are just beginning to attempt to modify a mosquito so it

can deliver a vaccine to people and livestock it bites. In tropical regions, such an insect could safeguard millions of people from polio and measles, vaccinating children who simply wouldn't be vaccinated otherwise.

Closer to fruition is research to prevent Chagas disease, an illness transmitted by the so-called "kissing bug," so named because it comes out at nighttime and bites people in the face. The bugs are born in the crevices of homes made of adobe and thatch, so the disease is most

prevalent among "people who live in homes of poor construction" across much of South America, said Durvasula.

In some people, Chagas disease causes an acute flu-like illness then, decades later, it causes heart disease and gastrointestinal disease. Chagas disease is not only transmitted from bug to human but it also tends to contaminate a country's blood supply, said Durvasula. "After a

disaster, there is sometimes a larger need for blood transfusions and contaminated blood would mean a greater risk of transmission," he

said.

The kissing bug transmits disease through protozoa in its digestive system. Durvasula and others may have found a way to "break that cycle

of transmission," he said, by making the kissing bug's insides an inhospitable place for the tiny parasites. They took bacteria that commonly live inside kissing bugs, then spliced in a moth gene so the bacteria produce a substance that kills the Chagas protozoa.

Baby kissing bugs dine on the dung of their parents. To get the modified bacteria inside the kissing bug, they mixed a black paste that looks like the dung -- only it's laced with the modified bacteria.

To test it, they built a Guatemalan-style hut inside a tightly sealed greenhouse on the Centers for Disease Control (CDC) campus in Atlanta.

In March, they'll release kissing bugs into the hut. Next year they'll conduct open-air field trials in Guatemala, where the CDC has a research station.

"The field trials will be led by the Guatemalans. This research effort has been a partnership. We're already working with field technicians

from villages in Guatemala where the disease is quite endemic. We've had a good reception from the beginning," said Durvasula.

Besides work like Durvasula's that potentially wards off disease, scientists also hope to give beneficial insects such as honeybees immunity to disease and pesticides.

Unlike genetically modified crops, there is so far a near absence of corporations that have invested in bio-bugs. Still, researchers see bio-bugs are a potential way to attack harmful insects without using chemicals.

Scientists acknowledge that what works in the lab might not work in the wild. Field tests must be carefully controlled because it would be impossible to recall freed insects in the face of unexpected consequences.

The Department of Transportation will soon issue guidelines on transporting bio-bugs, and the USDA already has clear guidelines for field experiments. "There is an established regulatory fabric out there that's being filled in," said O'Brochta.


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