Edition: U.S. / Global

SCIENCE WATCH; War Against Parasite

Published: August 27, 1991

United States officials are planning to use satellite imagery to track and eventually eliminate a parasitic enemy in Central America.

The screwworm, a parasite of warm-blooded animals that at one time caused more than $50 million in damage a year to the Texas cattle industry, is the focus of a joint effort by the Federal Department of Agriculture and space researchers at the University of Texas at Austin.

The analysis of satellite imagery will be used to identify likely habitats of the screwworm and will allow for more extensive searches at lower cost than conventional methods.

Researchers will combine imagery from United States and Soviet satellites, aerial photography and ground surveys to track the screwworm population.

Agriculture officials eliminated the parasite from the United States and Mexico by introducing male flies sterilized by radiation into the screwworm population, taking advantage of the female screwworm's short one-month mating period. The new goal is to use sterilized male flies to push the parasite south of Panama.

The screwworm fly lays up to 300 eggs on open wounds or on the umbilical cords of newborn animals, said Dr. John Welch, a Federal entomologist. The larvae feed off the animal for five days, often causing life-threatening infections.

"The larvae can kill a full-grown steer in 10 days if left untreated," Dr. Welch said.