From: Reuters
Published April 23, 2008 03:27 PM

Fight against tropical ill slowed by superbug fears

By Mica Rosenberg

COMAPA, Guatemala (Reuters) - Guatemalan health inspectors scour Lucinda Bautista's mud hut with flashlights and tweezers, plucking killer bugs from cracks in the walls.

The cockroach-sized insects usually suck blood from around victims' mouths and carry the Chagas disease, which infects nearly 10 million people in Latin America a year and kills tens of thousands.

Several fumigations of Bautista's home near the town of Comapa have failed to wipe out the bugs, known as "chinches." An infested house can have thousands of them hiding in crevices.

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"They have sprayed here many times but the bugs are still in the walls and they bite all of us all the time," said Bautista, 40, clutching one of her three children.

The estimated death toll of 20,000 a year from Chagas is likely low since most people have no symptoms until years later when they develop heart disease that could cause cardiac arrest.

Poor residents of Guatemala's dry, eastern state of Jutiapa like Bautista are desperately in need of a new way to keep the bugs at bay.

U.S. and Guatemalan scientists have discovered how to genetically modify a bacteria inside the chinche to kill the disease, but field trials have been stifled by fears of creating a science-fiction style superbug if the transgenic chinches are released from the lab.

"Putting these transgenes into something that can move around, where those genes can jump over to other things or potentially mutate is completely new territory," said Ravi Durvasula of the University of New Mexico who designed the experiments.

"Nothing really comes close to this ... That might be part of the reluctance," said Durvasula who is working with scientists at the U.S. Centers for Disease Control and Prevention in Atlanta on fighting Chagas.

Durvasula's team wanted to launch trials in Guatemala but has been waiting for years for government regulators to set rules for the release.

NASTY HABIT

The bugs' feces carries Chagas and their nasty habit of defecating where they feed means a quick scratch of the bite mark is enough to transmit the disease into a human's bloodstream.

Fumigation programs and efforts to build better housing in countries like Brazil have led to dramatic declines in Chagas infections in recent years.

But in places like Jutiapa there is a different kind of flying chinche that lives in trees and can easily re-infest a house after fumigation.

The CDC's genetically engineered bacterium is fed to baby chinches and once inside the bugs can kill the Chagas parasite, known as Trypanosoma cruzi.

Lab tests showed the genetically modified bacteria that killed the parasite was spread successfully through a test population of chinches.

The next step would be controlled field trials of the method to see if it works in the wild, but U.S. scientists complain there is a big vacuum in current laws regulating bioengineered insects.

"The problem is when a new application comes along sometimes it falls between agencies," said entomologist Thomas Miller at the University of California Riverside who helped to develop a genetically modified cotton-eating pest.

"Some of these new technologies weren't in existence when the laws were written. There hasn't been someone to take an overall approach," said Miller.

The prospect of genetically engineered insects, some which could bite people like Bautista and her small children, raises even more complicated questions than genetically modified foods.

"Any time you affect the ecosystem trying to modify a vector there is a risk the vector could become something else," said Peter Hotez, the president of the Sabin Vaccine Institute and an expert in neglected tropical diseases like Chagas.

(Editing by Cynthia Osterman)

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