SCOTT SIMON, HOST:
There's a worry in cattle country about a deadly insect that could soon threaten herds from California to Florida, and it sounds like something out of a horror film.
COLIN WOODALL: The New World screwworm is, in essence, a flesh-eating parasite.
SIMON: Colin Woodall is CEO of the National Cattlemen's Beef Association, and his family runs a small cow-calf farm in Texas. The screwworm is actually a fly. Females lay their eggs in living animals, including livestock.
WOODALL: The larva does exactly what the name would suggest. It screws or bores into the flesh of our cattle and, in essence, eats the animal from the inside out. It is a horrific parasite.
SIMON: And if left untreated, the animal can die within a week. Older cattlemen tell stories of fighting the parasite back in the 1940s and '50s. The screwworm was successfully eradicated from the U.S. in 1966. But now the Department of Agriculture is preparing for battle again, and the plan involves fighting flies with billions of more flies. Dr. Edwin Burgess is a veterinary entomologist at the University of Florida. He joins us from Gainesville. Thanks so much for being with us.
EDWIN BURGESS: It's a pleasure to be talking to you, and thanks for having me.
SIMON: How does the Department of Agriculture plan to try and eradicate screwworms this time?
BURGESS: So we're going to use the same strategy that we used the last time, which is a technique called the sterile insect technique. And it was used to great success and even fame in the 1960s.
SIMON: Forgive me. How do you sterilize a screwworm?
BURGESS: What happens is these facilities will rear this fly in very, very large numbers, and they irradiate them. And that irradiation process is what sterilizes them. They take just the males, and then they package them up and fly them over large areas and drop these little packets out of planes. And then those adult male flies mate with the females. And what's interesting about this fly is that they - females mate primarily one time in their life. And so if a female mates with a sterile male, she cannot fertilize her eggs, and so she cannot contribute to the population. Eventually, you crash the population of the fly.
SIMON: Where are the screwworms now, and how quickly are they advancing?
BURGESS: They are currently in Mexico. They have gone past Central America, and they are making a northward movement. The flies are very strong fliers. A female can fly about 300 kilometers in her lifetime. They disperse pretty widely.
SIMON: And this is preferable to pesticides because it's just less toxic?
BURGESS: It is that. But it is also definitely the biology of the fly because this fly is very low abundance and distributes widely and isn't, you know, visually apparent everywhere. It makes utilizing chemicals in the environment not the best strategy because you would be killing very few of them with your efforts with that.
SIMON: And forgive the naivety of this question, but why are they coming north?
BURGESS: That's a very, very good question. This is historically a tropical fly. So it's primarily isolated in the southern United States and in states like Florida, where that tropical climate can sustain its life throughout the entire year.
SIMON: And could the sterilization method be used for other pests?
BURGESS: Yes, actually. But one of the key features of a sterile insect technique is going to be that single mating. And so there are a number of other types of flies - believe it or not, a mosquito is actually a fly. There are strategies that are being developed to use this technique to control mosquitoes, as well. But it does not work on all insects 'cause not all insects mate one time.
SIMON: Dr. Edwin Burgess, a veterinary entomologist. Thanks so much.
BURGESS: Yeah. Thank you for having me. Transcript provided by NPR, Copyright NPR.
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