MercoPress. South Atlantic News Agency

“Sterile flies” to combat cattle screw worm in Uruguay

Sterile fly

Mexico made a first shipment of sterile parasitic flies to Uruguay to help combat the cattle “screw worm” or Cochliomyia hominivorax, an insect whose larvae or maggots eat living tissue, and which has gradually spread from Brazil to the southern pastures of South America.

Mexican sanitary authorities said the sterile flies will be set free in the north of Uruguay in a trial test zone, next to Brazil to see if it is possible to eradicate the parasitic fly. The authorities added it is part on an ongoing program of bio-technical assistance together with Brazil, Paraguay and Uruguay coordinated by the Mexican American Commission for the eradication of the parasitic screw worm or SENASICA. The pilot test in Uruguay is partly financed by the Inter-American Development Bank and includes taking samples of maggots from infested animals, treating wound, monitor cattle movements and dispersion of the parasitic flies in the test area. "We hope this test can set the foundations for a regional program to eradicate the parasite disease in the Southern Cone", said the Mexican Foreign Office in an official release. Mexico recalled that it has successfully eradicated the disease in most of the cattle breeding areas of the country and also has a "sterile flies" farm in the state of Chiapas, "the only one in the world" with which to fight the deadly maggots that cost hundreds of millions of US dollars annually to the cattle industry. Contrary to other flies which feed on dead flesh and occasionally infest a putrid wound, the Cochliomyia screw-worm maggots are unusual because they attack healthy tissue. According to technical information, screw-worm females lay 250-500 eggs in the exposed flesh of warm-blooded animals, including humans, such as in wounds and the navels of newly-born animals. The larvae hatch and burrow into the surrounding tissue as they feed. If the wound is disturbed during this time the larvae burrow or "screw" deeper into the flesh, which is the source of the insect's name. The maggots are capable of causing severe tissue damage or even death to the host. Approximately three to seven days after hatching the larvae fall to the ground to pupate. The pupae reach the adult stage about seven days later. Female screw-worm flies mate four to five days after hatching. The entire life cycle is approximately twenty days. A female can lay up to 3,000 eggs and fly up to 200 km (125 miles) during her life. Using the sterile insect bio-technique United States officially eradicated the screw-worm in 1982; in 1994 it was eradicated in Guatemala and Belize; 1995, El Salvador and Honduras 1996. Campaigns continue in Mexico, Nicaragua, Costa Rica and Jamaica.