Mexico declares war on deadly flesh-eating fly
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Pastor Dale Morgan
Sep 7, 2010, 4:47:32 PM9/7/10
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Plagues, Pestilences and Diseases
Mexico declares war on deadly flesh-eating fly
Parasite that costs Latin America $1.5bn a year is target of growing infertility campaign
* Frédéric Saliba
* Guardian Weekly, Tuesday 7 September 2010 14.00 BST
Head of Screw-Worm Fly Close encounter ... the head of a screw-worm fly. Photograph: David Scharf/Science Faction/Corbis
You have to undress to enter this extraordinary breeding centre for Cochliomyia hominivorax, or screwworm. In southern Mexico the farmers call them killer flies. "If we want to eradicate this dangerous species, we can't allow any insects or fertile larvae to escape," said the production head, Arturo Martinez y Tapia.
Located some 20km from the Chiapas state capital Tuxtla Gutierrez, this 80-hectare plant is guarded by the Mexican army. "Here we produce and sterilise between 120 and 500 million flies per week," explained Martinez y Tapia, a 60-year-old vet, before putting on his safety overalls, headgear and boots.
To enter this fortress you have to pass through a double-entrance sealed hatch and a sheet of compressed air. A vile smell hits you as soon as you step inside. "Its the ammonia produced by the larvae's metabolic waste," said Martinez y Tapia as we entered the vast breeding room packed with cages, each swarming with flies. The buzzing sound makes your head spin.
This red-eyed insect is endemic in the Americas. It lays its eggs close to wounds and the natural orifices of warm-blooded mammals, including humans. Once its eggs have hatched, the larvae pierce the skin by means of two carnassial teeth and start munching – hence its Latin name, which means "man-eating fly".
The species was discovered in 1858 by a French doctor, Charles Coquerel. He found them on convicts in Devil's Island in Guyana. Today livestock are the main victims of the larvae, and according to Martinez y Tapia the resulting economic losses are estimated at $1.5bn per year in Latin America.
In 1972 the Mexican and US governments decided to combat the pest by setting up the Mexico-American Commission for the Eradication of the Screwworm (Comexa) in Tuxtla Gutierrez and using the Sterile Insect Technique (SIT). This was invented in 1940 by two American entomologists, Edward Fred Knipling and Raymond C Bushland. It has been updated since then and consists of breeding flies on a large scale and sterilising them with gamma radiation before releasing them. The eggs resulting from reproduction between these flies and "normal" ones are infertile.
The air is suffocating in the egg-collecting rooms, with temperatures in the 40°c and 80% humidity. Each fly lays around 250 eggs on moss-covered sticks placed in cages and covered with an evil-smelling fermented mixture.
"When the eggs have hatched, the larvae start feeding on a mixture of blood, powdered egg, soy, cellulose fibre and water," said René Soliz, one of the biologists.
Once mature, the larvae move off the trays and fall into channels on the floor, where they are collected before the next stage, the transformation into pupae. The cocoons are placed in perforated cylinders and introduced into one of the three Cesium-137 irradiation machines.
Grisel Molina who supervises this part, explained that the nuclear rays damaged the reproductive cells without affecting the other organs.This is a tried and tested method. The screwworm was eliminated in the US as early as 1966 but only 25 years later in Mexico. However, the parasite continues to wreck havoc elsewhere in south America and the Caribbean, so billions of irradiated pupae are packed into boxes in Mexico and sent by air to Brazil and Uruguay, and soon also to Cuba and Haiti. "This is an ecological method that prevents the use of insecticides. But it does mean concentrating a very large number of sterile insects – 10 for every natural one – in a given geographic area," said Martinez y Tapia.
"Our objective is to eradicate the species in the south of the continent," said Comexa's director, Alejandro Parra. Eduardo Garcia, from the Brazilian ministry of agriculture, added: "It is a cumbersome technique, but our cattle losses make it well worthwhile."
Large sums of money and regional co-operation are necessary to make this action truly effective. Mexico devoted $800m over 19 years to achieve its goal.
Complete eradication of the fly could cost Latin American countries several billion dollars spread over 15-30 years. The success of the operation depends very much on the political will of the countries' leaders.
This article originally appeared in Le Monde
Mexico declares war on deadly flesh-eating fly
Parasite that costs Latin America $1.5bn a year is target of growing infertility campaign
* Frédéric Saliba
* Guardian Weekly, Tuesday 7 September 2010 14.00 BST
Head of Screw-Worm Fly Close encounter ... the head of a screw-worm fly. Photograph: David Scharf/Science Faction/Corbis
You have to undress to enter this extraordinary breeding centre for Cochliomyia hominivorax, or screwworm. In southern Mexico the farmers call them killer flies. "If we want to eradicate this dangerous species, we can't allow any insects or fertile larvae to escape," said the production head, Arturo Martinez y Tapia.
Located some 20km from the Chiapas state capital Tuxtla Gutierrez, this 80-hectare plant is guarded by the Mexican army. "Here we produce and sterilise between 120 and 500 million flies per week," explained Martinez y Tapia, a 60-year-old vet, before putting on his safety overalls, headgear and boots.
To enter this fortress you have to pass through a double-entrance sealed hatch and a sheet of compressed air. A vile smell hits you as soon as you step inside. "Its the ammonia produced by the larvae's metabolic waste," said Martinez y Tapia as we entered the vast breeding room packed with cages, each swarming with flies. The buzzing sound makes your head spin.
This red-eyed insect is endemic in the Americas. It lays its eggs close to wounds and the natural orifices of warm-blooded mammals, including humans. Once its eggs have hatched, the larvae pierce the skin by means of two carnassial teeth and start munching – hence its Latin name, which means "man-eating fly".
The species was discovered in 1858 by a French doctor, Charles Coquerel. He found them on convicts in Devil's Island in Guyana. Today livestock are the main victims of the larvae, and according to Martinez y Tapia the resulting economic losses are estimated at $1.5bn per year in Latin America.
In 1972 the Mexican and US governments decided to combat the pest by setting up the Mexico-American Commission for the Eradication of the Screwworm (Comexa) in Tuxtla Gutierrez and using the Sterile Insect Technique (SIT). This was invented in 1940 by two American entomologists, Edward Fred Knipling and Raymond C Bushland. It has been updated since then and consists of breeding flies on a large scale and sterilising them with gamma radiation before releasing them. The eggs resulting from reproduction between these flies and "normal" ones are infertile.
The air is suffocating in the egg-collecting rooms, with temperatures in the 40°c and 80% humidity. Each fly lays around 250 eggs on moss-covered sticks placed in cages and covered with an evil-smelling fermented mixture.
"When the eggs have hatched, the larvae start feeding on a mixture of blood, powdered egg, soy, cellulose fibre and water," said René Soliz, one of the biologists.
Once mature, the larvae move off the trays and fall into channels on the floor, where they are collected before the next stage, the transformation into pupae. The cocoons are placed in perforated cylinders and introduced into one of the three Cesium-137 irradiation machines.
Grisel Molina who supervises this part, explained that the nuclear rays damaged the reproductive cells without affecting the other organs.This is a tried and tested method. The screwworm was eliminated in the US as early as 1966 but only 25 years later in Mexico. However, the parasite continues to wreck havoc elsewhere in south America and the Caribbean, so billions of irradiated pupae are packed into boxes in Mexico and sent by air to Brazil and Uruguay, and soon also to Cuba and Haiti. "This is an ecological method that prevents the use of insecticides. But it does mean concentrating a very large number of sterile insects – 10 for every natural one – in a given geographic area," said Martinez y Tapia.
"Our objective is to eradicate the species in the south of the continent," said Comexa's director, Alejandro Parra. Eduardo Garcia, from the Brazilian ministry of agriculture, added: "It is a cumbersome technique, but our cattle losses make it well worthwhile."
Large sums of money and regional co-operation are necessary to make this action truly effective. Mexico devoted $800m over 19 years to achieve its goal.
Complete eradication of the fly could cost Latin American countries several billion dollars spread over 15-30 years. The success of the operation depends very much on the political will of the countries' leaders.
This article originally appeared in Le Monde
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