rewrite this title Texas has detected a flesh-eating parasite in livestock after 60 years

Texas officials announced they have detected the New World screwworm in livestock, the first evidence of the parasite in that state in decades.

AYESHA RASCOE, HOST:

A flesh-eating parasite known as the New World screwworm has officially made its way across the U.S.-Mexico border. Last week, the U.S. Department of Agriculture announced it detected the pest in livestock – two calves in South Texas. These are the first confirmed cases in that state in 60 years. For decades, agricultural officials have tried to keep the bug from gaining a foothold here because of the threat it poses to the nation’s livestock. NPR health correspondent Will Stone joins us with an update. Hi, Will.

WILL STONE, BYLINE: Hey there.

RASCOE: So why is this parasite reaching Texas such a cause for concern?

STONE: Yeah. Historically, the screwworm, which is not a worm, actually – it’s a parasitic fly – was one of the most devastating livestock pests in the U.S. It was once widespread in the South, and there were millions of cases in cattle in Texas every year. The economic fallout was huge, which is why the eradication program in the mid-1900s was considered such a success story. That’s when the U.S. government began releasing millions of sterile male flies. Those mate with wild females, which means they don’t produce any viable offspring. This effort, over many years, eventually expanded into Mexico and Central America. But in the last few years, the fly has made a northern migration up from Panama, and experts believed it was just a matter of time before it arrived here.

RASCOE: OK, so what are U.S. officials doing to contain this?

STONE: Well, they’re taking this incredibly seriously. They have teams down in South Texas. They’ve established a containment zone around the area, and they’re restricting movement of animals as well as ramping up surveillance. Here’s what Agriculture Secretary Brooke Rollins told reporters the other day.

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BROOKE ROLLINS: If we all work together and follow these treatment and movement restriction guidelines, there is no reason to believe that this incursion will result in any sort of establishment of the pest on our side of the border.

STONE: Rollins says her agency is also releasing millions of these sterile flies in Texas, and they’re ramping up efforts to do this in Mexico as well.

RASCOE: Will, as we mentioned at the top, these are flesh-eating parasites. Like, can you tell us more about them?

STONE: Sure. The details can be a bit gruesome. The female screwworm flies lay their eggs in the wound, sometimes in the mucus membranes. Then when they hatch, these maggots start feeding on the flesh. And we’re primarily talking about cattle here, though this is also a concern for wildlife. I got a pretty vivid description from Edwin Burgess. He’s a professor of veterinary entomology at the University of Florida. Take a listen.

EDWIN BURGESS: Their mouth end is very sharpened, and their posterior end is very flat. And then along the outside of their body, they have these rigid hairs. They contract and expand, and they use those hairs as kind of grip to move through the tissues. And those rows of hairs take kind of a corkscrew shape.

STONE: So that’s at least partly where the name screwworm comes from. Now, an infestation can be fatal, but Burgess says if it’s caught early enough, you can treat this, and the animal will survive. One challenge is that larvae can fall off a wound and burrow into the soil where they can hide out. So that’s why you need to release massive numbers of sterile flies in an affected area to stamp them out.

RASCOE: Clearly, this is a risk for livestock and wildlife, but does it pose any immediate threat to humans?

STONE: Cases in humans do happen, though they are rare. And generally speaking, the risk is considered quite low, and it would only be for people in the immediate vicinity. And just to be clear, this isn’t an infectious disease like a virus that someone catches and then spreads to someone else. The fly needs to find somewhere to lay its eggs. Federal officials and Burgess all stress the food chain is safe. Folks don’t need to worry about finding these parasites in their meat. I spoke to Jason Sawyer, who is chief science officer for East Foundation. That’s a nonprofit that operates ranches in South Texas. Overall, he feels pretty optimistic the U.S. can keep this from escalating.

JASON SAWYER: You know, we’ve done it before. We can do it again. You just have to have the right tools in the toolbox.

STONE: Sawyer told me there had been active cases south of the border for months now. So like others in his industry, they’ve been taking extra precautions and preparing in case they do find the screwworm in their cattle.

RASCOE: That’s NPR health correspondent Will Stone. Thank you so much for speaking with us today.

STONE: You’re welcome.

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