FEATURE - Grisly Mexico factory breeds man-eating flies
Date: 25-Feb-03
Country: MEXICO
Author: Elizabeth Fullerton
Tuxtla Gutierrez, the capital of Chiapas, better known for spawning an armed rebellion in 1994 by guerrillas fighting for Indian rights, is home to the world's only New World screwworm plant, breeding millions of insects each week.
Named for the corkscrew motion with which they burrow into flesh, the screwworm larvae can kill their victim - human or animal - in five days. The worm's Latin name, cochliomyia hominivorax, means "fly that devours men".
"They feed off fresh blood, not dead tissue as other species do. That's why they are extremely dangerous. It's very hard for an animal to defend itself against something like that," said Alfredo Alvarez, a biologist at the plant.
In the 1950s, U.S. scientists pioneered a strange but effective way of eradicating the pests. The flies are zapped with high doses of radiation to sterilize them then released into the wild to mate with their fertile counterparts.
The females only mate once, so if they do so with the sterile flies, they will not reproduce.
Using this technology, the United States by 1982 wiped out the bug that had threatened swathes of the nation's livestock.
With the aim of gradually eradicating the worm from the American continent, the fly-producing factory in southern Mexico was started in 1976 by a joint U.S.-Mexican government commission and by 1992 Mexico was declared free of the screwworm.
But there have been recurrences in Mexico recent years, some, ironically, due to errors at the fly factory that allowed millions of the killer flies to escape.
Machine failure at the plant caused an outbreak of the disease in January that Alvarez described as a "disaster."
But thanks to the 27-year-old plant, the flies have been mostly wiped out in the southern United States, Mexico, Libya and across most of Central America.
In the early 1990s, Mexico exported the flies to Libya, which was contaminated by South American cattle imports.
The U.S.-Mexican commission is now selling its unusual product to Panama and Jamaica, where what look like cardboard lunch-boxes packed with black buzzing flies are dropped from planes to rid those areas of the bloodthirsty insect.
VITAL ORGANS
A fetid, overbearing stench of decay - the odor from the waste that about 90 million flies produce each week - hits a visitor on arrival at the fly plant.
It pervades clothing, hair and nostrils long after one leaves the plant, despite obligatory rigorous showering.
Security is tight. All visitors and personnel are given clean overalls and boots for entering the production area, which is locked after them and has no windows.
In the so-called "fly colony," a loud buzzing emanates from row upon row of metal cages where thousands of fertile flies are kept alive and fattened for breeding.
To the untrained eye, they resemble common house flies with blue-green bodies but these have bulging orange eyes.
After seven days, the flies are mature enough to lay their eggs and are taken to a darkened room. They lay their eggs along long wooden sticks smeared with a gel that to them smells similar to a wound. The fly's average life cycle is 20 days.
One fly can lay up to 400 eggs in a wound. Within 24 hours these hatch into larvae and begin burrowing into the meat.
In two days, an open sore in an eye, for example, will turn into a grapefruit-sized festering wound of raw, pulpy flesh. The larvae eat their way towards the victim's vital organs.
"If the wound is in the stomach, they'll try to get to the liver or intestines. If it's in the head, they'll attack the eyes, the ears. They can reach the brain and then it's adios," said Alvarez, who is employed by the U.S. Department of Agriculture's Agricultural Research Service.
The worm comes in two species - the New World screwworm, native to the Western Hemisphere, and the Old World screwworm, found in Southeast Asia, the Middle East and parts of Africa.
TRICKING THE WORMS
In the incubation room, live wounds