Pod Insights This Podcast Will Kill You Ep 192 New World Screwworm: Oh-oh here they come About this episode It’s the stuff nightmares are made of. A fly lands on an open wound and lays hundreds of eggs, from which hatch countless ravenous maggots. There they writhe, devouring flesh, insatiable and relentless. Every minute they dig deeper and deeper until flesh gives way to bone. Even the species name of these maggots inspires a shiver of fear: Cochliomyia hominivorax - “man eater”. This nightmare of a fly is the horrifying reality for many mammals in South America and some Caribbean islands, particularly cattle. And it seems to be making a comeback in the places it was previously eradicated - Central and North America. What exactly this fly does, why it’s such a problem, and how we came to defeat it (temporarily) all feature in this week’s episode. Sterile flies? Archival footage? Gnarly descriptions? This episode has it all.
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Transcript 11,694 words · 7 speakers
0:01 Speaker 00 This is Exactly Right.
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0:38 Speaker 01 Hey, I'm Niall Rogers. This fall, I'll be driving across the country, meeting some of today's coolest and most fascinating artists. We'll explore the stories before the moments that changed everything. Because every musician remembers the moment where it all began. Experience Before the Moment, a Lincoln Original Series on the iHeartRadio app, YouTube, or wherever you get your podcasts.
1:09 Speaker 02 One screw worm infestation that goes unreported could erase the tremendous gains that have been made in the Southwest against this insidious, multimillion-dollar pest, the screw worm. Eradication workers can protect the gains, but only if they know where the pest strikes. You can help. Stopping screw worms is your concern, especially if you own livestock, or a dog, or a cat, or any other pet. All of you can help by finding and reporting screw worm infestations. Examine your animals at every opportunity. Look for cuts, scratches, or other wounds. If you find a wound that contains insect eggs or larvae, take about a dozen worms and all eggs from the wound. After you've taken the samples, treat the wound with approved insecticides.
1:54 Speaker 02 Place the samples in a container or jar, in alcohol or water. At this point, speed is important. Call your county agent. He'll tell you where to send the samples. He'll tell you what action to take.
2:09 Speaker 02 Positive identification will be made by experts and measures taken to eliminate the parasite. A screw worm infestation confirmed by positive identification sets off a series of emergency activities at screw worm eradication headquarters at Mission, Texas. Here, millions of screw worm flies are being reared each day and made sexually sterile by exposure to gamma rays from radioactive cobalt. Released in special patterns and in large numbers, these laboratory reared flies fight for us against an outbreak. These sterile screw worm flies mate with native flies, which in turn cannot reproduce. Release of sterile flies, combined with intensive livestock inspection and use of insecticidal
2:52 Speaker 02 treatments, has already stemmed outbreaks. This new technique for insect control is eliminating screw worms from the southwest. Complete success depends on quick discovery, quick reporting, quick action. Remember, examine, collect, treat. Call your county agent and help stop screw worms.
4:03 Speaker 03 That's the whole episode, is it not? Isn't that amazing?
4:08 Speaker 00 So comprehensive.
4:09 Speaker 03 It's so comprehensive. I, okay, so that was from, I found that on, in the USDA National Agricultural Library in like their screw worm exhibit. And it was a video produced in 1963 and it's called Lookout for Screwworms. And I just, it was, I think I didn't realize the extent to which screw worm was such a big deal during that time period, for decades and decades and decades. Enough so that there are like promotional videos like this.
4:45 Speaker 00 Right. I, I'm really excited, Erin, to hear you talk about the history because I was reading and didn't realize like a lot of the history of like ranching in the US was driven by screw worm.
4:57 Speaker 03 Yeah. I know, I know. And it's so funny. Yeah. I mean, there's, there's so much to cover. We'll get into all of it. I like wanted to start right now, but.
5:06 Speaker 00 Yeah, I want you to.
5:08 Speaker 03 We'll start instead with introductions. Hi, I'm Erin Welsh.
5:13 Speaker 00 And I'm Erin Allman-Update.
5:14 Speaker 03 This is, this podcast will kill you.
5:17 Speaker 00 And today we're talking about screw worms.
5:19 Speaker 03 Screw worms. Specifically for my, for me, I'm talking about new world screw worm.
5:23 Speaker 00 Yeah, well, we'll go over both different types of screw worms, new world and old world. But realistically, we're mostly talking about new world screw worm today.
5:32 Speaker 03 The one that's been in the headlines.
5:34 Speaker 00 In the news.
5:36 Speaker 03 Been in the news.
5:37 Speaker 00 Big time.
5:38 Speaker 03 It's gonna be a really interesting episode and a little bit maybe creepy crawly.
5:44 Speaker 00 Only a little bit.
5:45 Speaker 03 A very, very creepy crawly. Yeah, some of the descriptions I have are hard to stomach.
5:51 Speaker 00 Okay, that's good. I don't have that many of those.
5:54 Speaker 03 Okay, okay.
5:55 Speaker 00 I'm keeping it basic.
5:57 Speaker 03 But before we get into all of that, it is quarantine time.
6:01 Speaker 00 Time.
6:02 Speaker 03 Yeah. What are we drinking this week?
6:04 Speaker 00 We're drinking the screw worm driver.
6:06 Speaker 03 Yeah.
6:07 Speaker 00 It was just a screwdriver.
6:08 Speaker 03 Screwdriver, which is vodka and orange juice and with the addition of a gummy worm.
6:15 Speaker 00 Gummy worm.
6:16 Speaker 03 To represent.
6:16 Speaker 00 Get a worm.
6:17 Speaker 03 Screw worm.
6:19 Speaker 00 We're getting real creative with these, Erin.
6:21 Speaker 03 You know, I think that's okay.
6:24 Speaker 00 It's totally fine.
6:26 Speaker 03 Okay. It has to be. It has to be.
6:30 Speaker 00 We can do nothing else.
6:31 Speaker 03 Yeah, yeah.
6:33 Speaker 00 We'll post the recipe on the places that you can find it, like our website, thispodcastwillkillyou.com someday, but also definitely on our socials, thispodcastwillkillyou. What? Socials.
6:44 Speaker 03 Oh, I have, I tried to post one. I don't know if it works very well. I can't figure out the dimensions, but hey, we're working on it.
6:50 Speaker 00 You know what? Listen.
6:52 Speaker 03 There's a way.
6:53 Speaker 00 There's a lot of other great stuff on our website.
6:55 Speaker 03 Yes, there is. We've got transcripts. We've got references for all of our episodes. So if you want to read more about Screwworm, that's a great place to go. We've got links to merch, to our bookshop.org affiliate account, to our Goodreads list, to music by Bloodmobile, contact us form, a submit your firsthand account form, Patreon, other things, probably. Check it out.
7:17 Speaker 00 There's a lot there. Thispodcastwillkillyou.com. If you haven't yet read, reviewed, and subscribed, please do that. We'd really love it. We're on YouTube, on the Exactly Right Network channel, and we're on all of your favorite podcatchers, including iHeartRadio, Apple Podcasts, Spotify, the like. Moving on.
7:35 Speaker 03 Moving on. Are we, are we done? Should we?
7:39 Speaker 00 Great. You ready?
7:39 Speaker 03 Yeah, I am.
7:40 Speaker 00 I'm going to tell you about the biology of Screwworm really fast so that you can tell me about the history.
7:46 Speaker 03 Okay, let's take a quick break and then we'll get to it.
8:21 Speaker 00 The star of today's show is the Screwworm, which is a larval form of a fly.
8:29 Speaker 00 Most people, when we say screw worm, mean the New World screw worm, which is the species Cochleomaya hominivorex. Might have pronounced that wrong. Homini- hominivorex. Listen. It's the New World screw worm. But there is another one, the Old World screw worm, which is a species called Crisoma beziana.
8:55 Speaker 03 Okay.
8:56 Speaker 00 And these are two different genera of fly, but both of them are blowflies. Overall, not entirely dissimilar to the flies whose larval forms not that long ago in an episode we hailed for the benefits of their ability to help heal wounds.
9:14 Speaker 03 Yeah, this may change our feelings on maggots, I think.
9:17 Speaker 00 It will. Because today, we're talking about pretty much the exact opposite.
9:22 Speaker 03 Yeah.
9:23 Speaker 00 Unlike most other species of blowfly, the New World and the Old World screw worms, larval forms feed not on necrotic or dead tissue, but instead on the warm and living tissue of warm-blooded animals.
9:41 Speaker 03 Yeah.
9:42 Speaker 00 So screw worms are a type of fly who lay their eggs in the flesh of living mammals in a way that causes really significant harm.
9:53 Speaker 03 Kind of like botflies, but more harmful.
9:56 Speaker 00 Way more harmful. So that, so what I want to do in this part of the episode is really just kind of take us through like, what are these flies? What do their life cycles look like? And why do they cause as much damage as they cause? So that you can tell us about all of the history with them, because I know it's really interesting. So adult flies of these, both of these species, they look fairly similar. Most of what I'm going to talk about is about Cochleomaya hominivorex, or the New World screw worm. But it mostly all applies to the Old World screw worm as well. They look a tiny bit different, but otherwise, they're really quite similar.
10:33 Speaker 03 I'm so interested in their evolutionary history, which I didn't look up, like, the relationship between them. Was it like independent? Yeah, anyway, like.
10:41 Speaker 00 Oh, I didn't look it up either, but that's really interesting. Like, how did they both end up evolving this way of life that's so different from all of their other brethren?
10:49 Speaker 03 Right. I mean, it's a, it's a great, you know, open niche, I guess. Like, yeah, someone else has got all the dead ones. You can get the live ones.
10:56 Speaker 00 Right, exactly.
10:59 Speaker 00 And so the adult flies, all entomologists everywhere are gonna kill me for saying this, they look like a fly.
11:05 Speaker 03 Okay. How big?
11:07 Speaker 00 How big? About a little bit larger than a horse, a housefly.
11:11 Speaker 03 Okay.
11:11 Speaker 00 Not, not a horsefly, housefly. And that's literally what they look like, because they are blowflies. A lot, a lot of the houseflies that we see, not houseflies, aren't necessarily blowflies, but you, you see these around. They've got almost like a metallic-ish, kind of bluish, greenish body, like most blowflies do. They have these big, giant, orangish eyes across their heads, and then they have these three black and gray stripes along their back. The old world screwworm has two of those stripes.
11:37 Speaker 03 Okay.
11:38 Speaker 00 The new world screwworms are native to essentially the entirety of the Americas, though they are primarily a tropical species. They need warm, moist soils in order to complete their life cycle, which goes something like this.
11:56 Speaker 00 The adult flies emerge from the soil where they pupate.
12:02 Speaker 00 And it is only the adult females, as is usual for flies, who cause the majority of the problems. They mate just one time. This is important.
12:14 Speaker 03 It's important.
12:15 Speaker 00 Usually around day three to five of life. And then they start laying eggs right around that time, day five to seven, after they come out of their pupal form. These flies lay 200 to 300 eggs. Some estimates say as much as 500 eggs per clutch. It keeps getting worse.
12:36 Speaker 03 Yep.
12:37 Speaker 00 Because they lay additional clutches every three to seven days for up to 11 clutches of 200 to 300 eggs in a lifetime. And we can err in math this, though we don't have to, because it's all over the papers. They lay a maximum of 3,000 eggs per single female screwworm fly throughout the course of their 20-plus day adult life.
13:02 Speaker 03 I mean, that is some hard work.
13:05 Speaker 00 It really is. They also often leave each one of their clutches in like several different egg masses.
13:14 Speaker 00 So not all like 200 in one spot. They'll lay them like over a course of a few minutes or a couple of hours in multiple times.
13:22 Speaker 03 Right. Don't put all your eggs in one lesion, kind of a mentality.
13:25 Speaker 00 Exactly, Erin, exactly. And they do, they lay their eggs in lesions on the margins of wounds on warm-blooded animals, mammals, possibly birds, though they don't tend to prefer birds, but they can, but all mammals. And they tend to prefer the kind of drier margins of fresh or bloody wounds compared to wounds that are severely infected or really wet or have a lot of like bacterial purulence.
13:58 Speaker 03 Right. They want the freshest of flesh.
14:01 Speaker 00 The freshest of flesh, and they especially prefer wounds that have already been infested with screw worms, kind of like a signal that gets sent out like, hey, this is a really great wound, go ahead and lay your eggs here. However, they can also lay their eggs on other easily accessible parts of our like thin skin or mucous membranes. So say the corners of eyes or in noses.
14:31 Speaker 03 Yep.
14:32 Speaker 00 Or near the perineum. Or especially in places like in say newborn mammals, like newborn cattle or goats or horses that have an umbilical, you know, stump that's not fully healed. That's a really common spot.
14:48 Speaker 03 Yeah.
14:49 Speaker 00 And then after a day or so, these eggs hatch into hundreds of maggots, the larval form of a fly. And these maggots eat their way in, around, and under the skin of their host, literally burying themselves in the process, which is how they get their name, screw worm.
15:16 Speaker 00 Their wriggly little maggot bodies are even grosser looking than most maggots. They have. Is that a thing that you can say?
15:25 Speaker 03 I mean, that is a high bar. Maggots are disgusting looking.
15:29 Speaker 00 Maggots are gross looking, 100%, but these ones have particularly sharp hooks as their mouthpieces.
15:37 Speaker 03 Yep.
15:38 Speaker 00 And their bodies have these sets of rings that kind of point backwards of these spines, these rings of like, you know, like the kind of spines where like you can drive over them, but don't drive backwards.
15:49 Speaker 03 Yep, yep, yep. Yeah.
15:51 Speaker 00 And that is what helps them literally corkscrew their way deep into the living tissues on which they're feeding.
15:59 Speaker 03 How big do these larvae get?
16:03 Speaker 00 Oh, that's a really good question. I actually didn't see anything about the particular sizes. I mean, they're not large. They're small individually. So like maybe a few millimeters big.
16:12 Speaker 03 Okay.
16:13 Speaker 00 They can, yeah. Um, they feed for about a week before dropping off to pupate in the soil for another week, and then they'll emerge as adult flies.
16:27 Speaker 03 And the once they emerge, okay, so I'm thinking about like going to in a place where screw worm is present. How many, you said that the females only mate once. And so how many rounds of females in a year is happening? You know what I mean?
16:44 Speaker 00 Oh, God.
16:45 Speaker 03 Right? It's not like a one time thing.
16:47 Speaker 00 I have no idea.
16:47 Speaker 03 If it's like one week, then do they overwinter, et cetera, that kind of stuff?
16:51 Speaker 00 Yeah. So, I mean, they tend to live in the tropics and in the tropics, they're there all year round, right? And so they're going to be continually and each female, adult females live for about 20 ish days. And then, you know, they're going to lay their eggs starting on day like four or five. And the eggs only take about a day before they hatch. And then they feed as larvae for about a week and then they pupate for about a week. And so their whole life cycle is maybe, what's that, like a month, a little more than a month?
17:24 Speaker 03 Okay.
17:24 Speaker 00 And so you could be getting 12 plus rounds. I mean, plus each female is laying like 3,000.
17:30 Speaker 03 Yeah.
17:31 Speaker 00 I can't even calculate it. That's a lot.
17:34 Speaker 03 It's just hard to comprehend, like, like, they, I feel like they would run out of living tissue to eat.
17:41 Speaker 00 It's an interesting, so it's actually really interesting that you say that because one of the, uh, one of the papers that I read was looking at like the, the overposition behavior of these flies. And they were pointing out that like, if you look at the way that they overposit and like how frequently they do it and how they lay their eggs in these like multiple different clutches and all of this. But they do it multiple times in their life, right? Like a lot of, a lot of flies or other insects might just lay like one giant clutch and then go ahead and die. Um, but the way that these particular screwflies do it, they, at least in this paper, were saying that this fits with this strategy of like exploitation where they might be
18:25 Speaker 00 evolutionarily finding niches that aren't always there, right? In an environment that's not always favorable. And so you've got to be able to like, take advantage, lay a whole bunch of eggs as soon as you can and as quickly as possible when you find the right wound because you don't know when you will again.
18:42 Speaker 03 Okay.
18:43 Speaker 00 Um, which suggests that in nature, the perfect wound overpositioned site might have been harder to come by, but then enter livestock.
18:54 Speaker 03 Livestock, yeah.
18:56 Speaker 00 And now there's basically free terrain because when I, before I started researching this and when I thought of like the wounds that screw worms were causing, but also that they were first laying their eggs in, I always thought of like a huge gaping like wound, right? Like some kind of large hole, some infected something. But actually that's not the right image to have. The types of wounds that these flies can overpos it in to begin with can be as small as a tick bite.
19:31 Speaker 03 And often are from a tick bite.
19:34 Speaker 00 Exactly. And so it's any break in the skin, a scratch from a thorn or a fence wire. Like I said, the belly buttons of newborn animals, insect bites. The wounds that can then be caused are incredibly substantial.
19:51 Speaker 03 Right.
19:52 Speaker 00 And animals, especially livestock animals, can die within a number of days to weeks after infestation with a screw worm, or it's multiple screw worms, because of how deeply these screw worms can wander and destroy tissue along their way, and because of things like secondary bacterial infections that can occur.
20:14 Speaker 03 Right.
20:15 Speaker 00 From, you know, just the open wound that is caused by these maggots.
20:19 Speaker 03 Mm hmm.
20:20 Speaker 00 So that's, that's like mostly screw worms, Erin.
20:24 Speaker 03 And, okay, so between the old world and new world, are there differences in the severity or in the number of eggs or, you know, whatever it is?
20:33 Speaker 00 It's a good question. It was like weirdly hard to find great papers on the old world screw worms. Um, so from what I can tell, they, they don't tend to be maybe quite as severe, or at least not as deadly as quickly.
20:46 Speaker 03 Okay, okay.
20:48 Speaker 00 Um, I don't, I don't know exactly why, like what are, you know, all of the specific differences between them. Um, as I know, you'll probably talk about the biggest difference in how we've dealt with them is that there are not as many programs that are widespread to try and eliminate the old world screw worm. So it is very much still a problem throughout its distribution.
21:09 Speaker 03 I see.
21:10 Speaker 00 Um, whereas we have changed the current distribution of the new world screw worm.
21:15 Speaker 03 Yeah. Against its will.
21:18 Speaker 00 Yeah. And then in terms of like, how do we manage it aside from what you're about to talk about? I just keep like putting little, putting little teasers out there. We don't have any kind of vaccine. We don't have any kind of like specific treatment for screw worms. It's basically when we're talking about livestock insecticides on the wounds or like insecticide dips and things to try and help prevent the screw worms infection to begin with. We can also use avermectins like ivermectin. So for humans with, when there is human infection, because there can be and there, there is. This is also a public health problem, not just a livestock problem.
22:00 Speaker 00 It requires oral ivermectin and this doesn't like get rid, get rid of the infection per se. What it does is paralyze the larvae, which then have to still be removed thereafter.
22:12 Speaker 03 Okay. It paralyzes the larvae. How interesting.
22:15 Speaker 00 Yeah. Yeah. So our mainstay of dealing with the new world screw worm has been sterile insect technique.
22:26 Speaker 03 It's so cool. Prevention.
22:28 Speaker 00 Tell me all about it.
22:31 Speaker 03 Is it my turn really?
22:33 Speaker 00 Yeah, I don't have any more.
22:34 Speaker 03 Great.
22:34 Speaker 00 I told you it was going to be basic and straightforward.
22:36 Speaker 03 I'm, I'm, I'm excited. All right, let's, let's get started.
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23:38 Speaker 01 Hey, it's Niall Rogers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by my friend, John Legend. So you're helping Will.i.am write hooks. What made "Ordinary People" become the one song from those sound checks you knew you had to make your own?
24:05 Speaker 04 I was just writing for the Black Eyed Peas. I wasn't expecting to write something for myself in that session, but I wrote the hook for "Ordinary People," and I recorded a demo, and I'm like, I would rather keep "Ordinary People" for myself. This station in Chicago, W G C I, they start playing it before we're promoting it. The song spoke for itself. It became the defining song for my first album. I knew it was special, but you never know how special it's going to be and how much impact it's going to have on people's lives. And you never believe that you're going to actually change people's lives with a song.
24:35 Speaker 01 Experience Before the Moment, a Lincoln original series on the iHeartRadio app, YouTube, or wherever you get your podcasts.
24:58 Speaker 03 So to help me set the stage for the history of Screw Worm, I've brought along some assistance. Erin. I can't wait. Please open the video titled Screw Worm 1.
25:17 Speaker 05 Three hundred million years before man appeared on Earth, the insect was here. With time to develop varieties so diverse, their numbers are beyond conception. Roughly a million species, along with ticks and mites, three-fourths of all the animal kingdom. Of these, ten thousand species are man's mortal foe, endlessly vying with him for food and fiber, endlessly looting what he has sown and tended.
26:05 Speaker 03 Did you like that?
26:06 Speaker 00 I loved it, Erin. I really hated the grub. Those were grubs, not maggots.
26:10 Speaker 03 Listen, the video is like everything. Grubs, grubs count.
26:14 Speaker 00 Oh, totes. That was clear.
26:16 Speaker 03 It's so fun. So that, I loved it so much. That video is from, it was produced by the US Department of Agriculture, the USDA, in 1969. And it goes into some of the various, like insect and plant pests, including screw worm that have been plaguing farmers across the globe. I also thought it was interesting because it was like 1 million species. And I looked it up, and I think we're now at like 5.5 million species.
26:41 Speaker 00 Yeah, I was like, that's such an underestimate.
26:43 Speaker 03 Right. It's like Dr. Evil, like 1 million dollars. Like, that's kind of what it reminded me of. 1 million insects. Yeah. But yeah, I went all in on video clips for this episode, as you're about to find out. So yeah, there's an amazing archive work at the National Agricultural Library on the USDA website, and as well as the Internet Archive, which is just one of my favorite things in existence. But, but I wanted to start the history of screw worm with that clip, because I feel like it transports us back to a time when New World screw worm was among the top threats to agriculture here in the US. And by the way, I'm gonna
27:24 Speaker 03 just be focusing pretty much only on New World screw worm for this, which I'm just calling screw worm for short.
27:30 Speaker 00 That's what most of the literature does. That's why it was hard for me to find stuff on Old World screw worm.
27:35 Speaker 03 Yeah. But its eradication from North and Central America in 1991, which spoilers, it was eradicated, and spoilers, it's back. It marked a tremendous achievement in pest control, and a demonstration of what was possible without the use of toxic pesticides. It was a big deal. Hence, the sheer volume of material that's out there about the screw worm eradication program. And after it was eradicated, it dropped out of the news cycle for the most part, except, of course, in the places where it was still prevalent, like most of South America. And the recent headlines about the reemergence of screw worm here in the US, that might be the first time that many people have learned about or heard of this parasite.
28:19 Speaker 03 But in fact, it has plagued wildlife, humans, livestock in the Western Hemisphere for thousands of years. And so using genetic analyses, researchers recreated the historical spread of this parasite and found that it seemed to follow human migration throughout the Americas.
28:37 Speaker 00 Interesting.
28:38 Speaker 03 Yeah. As human migration continued across North America and then down into Central and South America, the screw worm followed them. And then the introduction of European livestock, starting in the 1500s, of course, provided even more hosts. And wherever it went, as long as it found a host on which to feed, and it wasn't too picky, it'll pretty much feed on anything that has living flesh and with suitable-
29:05 Speaker 00 Except like reptiles.
29:06 Speaker 03 Yeah, yeah.
29:08 Speaker 00 Yeah. Worm flesh.
29:09 Speaker 03 Worm flesh, yep. And with suitable climate conditions, it would just do its horrific thing wherever it could. And so last season, we talked about how we did this episode on medicinal maggots and raved about how cool they are, which is so true. But the myiasis from screw worms is another matter entirely.
29:29 Speaker 00 It's not the same.
29:30 Speaker 03 It is not the same. I found a quote from C. E. Scruggs from 1975 that I think pretty much sums it up for me. Quote, "It is doubtful that the mind of man could create a more vile scene than that of worms consuming the live flesh of one's body. The imagination almost refuses, particularly in this day and age, to conjure up the horrendous pain and outright revulsion that must come to a person infested with a writhing, seething mass of worms steadily tearing and consuming his flesh," end quote.
30:05 Speaker 03 It's, I mean, it's truly awful. It is truly awful. Yeah.
30:10 Speaker 00 Yeah.
30:11 Speaker 03 And this feeling, this image, this sentiment towards myiasis, this might have been what the guy who first described the New World Screwworm was thinking when he gave it the name, the species name of Humminivorex, which is man eater.
30:27 Speaker 00 Man eater.
30:27 Speaker 03 What it translates to. And so the guy who did this was named Charles Coquere. He was a surgeon in the French Navy stationed at a penal colony, Cayenne in French Guiana in the mid 19th century. Conditions at this penal colony were so awful, apparently, that it was given the name Devil's Island. And while he was there, he treated five men who were suffering from screw worm infestation. Flies had laid eggs in each of their nostrils and masses of larvae developed in their nasal sinuses, consuming the surrounding tissue. I know. Three of the five men died as a result of these infestations and apparently 300 larvae were recovered after rinsing the sinuses out with water.
31:10 Speaker 00 Yeah.
31:11 Speaker 03 Yeah.
31:11 Speaker 00 Nasal passages seem to be a really commonplace when there's human infestation.
31:16 Speaker 03 I mean, it makes sense. You just can't get at it as easily. Yeah.
31:20 Speaker 00 Well, and, and a lot of times too, there's like, there's, there's something else going on. Like you, like you're in a, a place where you don't have access to be able to move around or clean your surroundings or whatever, or that you're sick with something else. So you're not able to like swat flies away. That's that sort of a thing. But it's still, it's, oh.
31:39 Speaker 03 It's, it's truly, it is truly awful. And I think that Coquere himself was quite a bit taken back by what he saw. And he wrote in this description of, of treating this, these men, that science is quote, powerless to prevent these terrible ravages.
31:56 Speaker 03 And in that, he would ultimately be proven wrong, but it would take another 100 years or so for science to have a fighting chance.
32:04 Speaker 00 Mm hmm.
32:05 Speaker 03 And in the meantime, screw worm continued its path of destruction. In the second half of the 1800s, cattle ranching expanded greatly across the southwest US, especially Texas, and millions of acres were transformed by grazing and also for grazing. Windmills were built to bring water to the surface for water holes. Screw worm flies like water, so that was one, you know, helping it along. Overgrazing meant fewer prairie fires, so more continuously occupied habitat, more continuous host for the screw worm.
32:41 Speaker 00 Okay.
32:41 Speaker 03 And deer replaced antelope as the dominant game animal, which grew even more abundant. So like deer herds, of course, are like, can be enormous. So that's like even more hosts for the flies.
32:52 Speaker 00 Mm hmm.
32:53 Speaker 03 According to one researcher's observation from 1959, deer are often victim to repeat infestations, leading to 2,000 to 3,000 larvae in one wound.
33:02 Speaker 00 Oh, goodness.
33:05 Speaker 03 And that amount of maggots, so 2,000 to 3,000, can destroy an area, apparently, seven inches wide and seven inches deep, or 18 centimeters wide and deep.
33:16 Speaker 00 Seven inches deep. I mean, how many areas on a deer's body can you go seven inches deep without hitting some vital structure?
33:25 Speaker 03 Yeah, I guess you, that's, you can't, yeah.
33:28 Speaker 00 Yeah.
33:29 Speaker 03 I mean, wounds, wounds like these are, can be deadly, are often deadly, and in bad years, up to 80% of fawns of whitetail deer were killed from these infestations.
33:38 Speaker 00 Oh.
33:39 Speaker 03 Yeah. And these deer also provided ample hosts for ticks, specifically the Gulf Coast tick or Ambleomimaculatum, which prefers to feed on the ears of livestock. And as we know, screw worms can lay their eggs in any wound, including tick bites, and cows' ears are often a casualty. You can tell, is this a screw worm infested area because all of their ears are just like gone or shriveled or, yeah, partially torn. And apparently, up to 90% of some of screw worm lesions start from a tick bite in some areas where the tick is especially prevalent. And then others through common farming practices like castration, branding, dehorning, and then like you mentioned, newborn livestock are often affected at the navel.
34:24 Speaker 03 And on top of that, so we've got all these things going on, right? Like, we've got more cattle, we've got water, we've got deer, we've got fewer prairie fires. This is all happening. And then you've also got the demand for beef skyrocketing since the development of refrigeration allows you to ship the meat that you don't sell locally, which previously had restricted herd size. And so now you've got the opportunity to create these massive herds because you can ship.
34:52 Speaker 00 Ship it.
34:53 Speaker 03 The meat.
34:53 Speaker 00 Oh, wow, Erin.
34:55 Speaker 03 Put it all together, and what you have are the perfect conditions for a screw worm storm.
35:01 Speaker 00 Just takeover.
35:02 Speaker 03 Just absolute takeover. And this parasite truly plagued the areas where they were established, and it was a horror for livestock owners. Quote, this is a quote from one of these owners. "A particularly disgusting and sickening job was when cows or calves got screw worms in their mouth and gums. This came about in two ways. One, the cow or calf, if they could reach the wound, would try to lick the worms out of the lesion. Thus, some live worms would get in the mouth of the animal and take hold. In some cases, I'm sure that flies would also lay eggs in the mouths of the newborn calves. You couldn't use any medicine. Just remove the worms and hope you get them all. Some cases would be so bad that an animal might lose some of their teeth.
35:45 Speaker 03 It sure wasn't a job for anyone with a queasy stomach." End quote.
35:50 Speaker 00 Oh, I've seen some pictures of that in, like, sheep's mouths, and it's so awful, Erin.
35:54 Speaker 03 Awful. And so you're trying, I mean, imagine you have a herd of cattle and you have to spend so much of your time trying to do this? Like, it was a losing battle, too, because, as you mentioned, infected lesions will attract more flies. So they ooze a, quote, "straw-colored and often bloody discharge that attracts more flies, resulting in multiple infestations by hundreds to thousands of maggots of all sizes. Death is inevitable unless the animal is found and treated." End quote.
36:29 Speaker 03 The horror of screw worm infestations was deepened by how inevitable they seemed. You could react, you could treat the animal, but how do you prevent them from attacking in the first place? Part of the issue was a misunderstanding of the screw worm's biology, which was only corrected in 1933. So for decades, the screw worm was misidentified as just a regular type of blowfly, one who primarily fed on carrion and only on live flesh sometimes. So it was like, okay, opportunistic live flesh feeder. And so it was thought, okay, well, if you get rid of all the carcasses on your rangeland, that is going to prevent the screw worm from
37:10 Speaker 00 I see.
37:11 Speaker 03 being a problem.
37:12 Speaker 00 Yeah.
37:13 Speaker 03 But since it feeds exclusively on live flesh, it actually doesn't really do anything.
37:17 Speaker 00 Right.
37:18 Speaker 03 And so recognizing that aspect of its biology was a huge step forward, and that happened in 1933. And around the same time, there was another development that would revolutionize the way that we dealt with screw worm. And that was the, a newly minted entomologist joining the cause. In 1934, Edward F. Nipling, a recent master's graduate from Iowa State University, started work at the USDA, where he was tasked with, among other things, collecting and counting screw worm flies caught in traps. Nipling was no stranger to screw worm. He grew up on a farm in rural southern Texas.
37:59 Speaker 03 He was one of 10 kids, and the farm is how they produced most of the food for this, his big family. So they would all be, you know, take part in, you know, dealing with the livestock. And he described removing, having to remove and look out for screw worms, among other agricultural pests. Before he went to college, he was aware of screw worm and the problems that it could cause, but it was at university that he gained a fuller perspective of how much insects have affected humanity, not just as livestock or agricultural pests, but also as vectors of disease, killing hundreds of millions of people around the world. He knew that control of these disease vectors and agricultural pests could save lives and livelihoods.
38:45 Speaker 03 And so while working at the USDA, he got to see firsthand how powerful some insecticides were, like DDT, which was just sort of like, you know, really this like revolutionary thing, kill it all.
38:59 Speaker 00 Yeah.
39:00 Speaker 03 And also how quickly they lost their potency as insects grew resistant, not to mention the toxic impacts of some of these pesticides.
39:07 Speaker 00 Right.
39:08 Speaker 03 And so he realized that a different, more proactive approach was needed. Erin, play the clip titled Screw Worm 2.
39:17 Speaker 00 Okay. This is so fun. Screw Worm 2.
39:23 Speaker 06 What we really need is some way to control the screw worms before they attack the animals. Rather than just wait until after the animal has had the screw worm and then try to control it. I realized that you would never, never really control the screw worm that way. What we needed was some preventive measure. But how to, how to control a screw worm on hundreds of thousands of square miles of
40:03 Speaker 06 territory, of course, seemed like a tremendous undertaking. And the use of insecticides or something like that seemed out of the question, and no doubt was. But then I conceived the idea that perhaps we could rear this screw worm and have it some, some genetic deficiency that then it would release and release those genetically deficient insects into the population.
40:48 Speaker 06 They would mate with the normal, normal flies and transmit detrimental characteristics. Just how I came to that conclusion, I, I really have a little difficulty even today. But...
41:08 Speaker 03 Isn't that amazing?
41:10 Speaker 00 He's like, I just kind of knew we had to do it. Don't know why I knew it, but I did.
41:15 Speaker 03 He's like, I did, yeah. He's like, I don't know. I have this brilliant idea and I have no idea how I came up with it.
41:22 Speaker 00 I love that.
41:23 Speaker 03 I love that. So that was, yeah, that was, that was Dr. Nipling himself interviewed in January 2000 as part of an oral history project for the scrotal eradication program.
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42:32 Speaker 01 Hey, it's Niall Rogers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by breakout singer-songwriter Alex Warren.
42:52 Speaker 00 I'm like a kid when I play music and I make music and I'm constantly asking questions. You know, whether it's an instrument I haven't played or it's a melody that seems foreign. You know, there's every night you play a show and it's the same set, but it's not the same show. At a certain point, your brain kind of goes on autopilot. When I'm in the studio or if I'm making music, that's where that curiosity kind of comes back, you know? I haven't lost it yet, but I'm also on my sophomore album. So, and you, you obviously are an expert here.
43:18 Speaker 01 Experience Before the Moment, a Lincoln original series on the iHeartRadio app, YouTube, or wherever you get your podcasts.
43:42 Speaker 03 And so what he's talking about here is what you mentioned, Erin, which is the sterile insect technique, which is an insect control measure where large numbers of flies are made sterile and then released, ultimately leading to a massive decrease in wild population sizes. And the idea behind this is that the sterile males that are released will mate with the females. They won't produce any eggs, and so there will be fewer and fewer screw worms over successive generations. And there are a few aspects of the screw worms biology that help this technique to be successful. The first is that screw worms, like you said, Erin, tend to mate just once. And so if they mate with a sterile male, there's no viable offspring. That's it.
44:26 Speaker 00 Yeah. And the females mate once, but the males mate like up to 10 times.
44:30 Speaker 03 Multiple times. Yes, yes.
44:31 Speaker 00 So one sterile male could be mating with 10 non-sterile females, and then they're not laying any eggs.
44:38 Speaker 03 Yep. Yep. And then the second thing is that in the screw worm affected areas in the US, which is more like subtropical, only a small proportion can survive over the winter. And so if you hit that area hard enough with sterile flies one year, you can really make a dramatic impact. And so that can really
44:59 Speaker 00 Really reduce that population size to begin with. That actually makes a lot of sense.
45:02 Speaker 03 Yeah. And Nipling wasn't the only one to come up with this idea or idea similar to this, like eradication or elimination via sterilization. There were a few other scientists that also proposed something similar in like the 1930s and 40s. But he was really the only one or the first one to get it off the ground. And for a number of years, you know, after coming up with this idea, he was like, okay, he had the idea first. And then he was like, how do I actually implement this? Like, what, how do I make them sterile?
45:32 Speaker 00 Yeah, right.
45:33 Speaker 03 And he, a colleague in 1950 was like, hey, have you, have you heard of this paper? Have you read this paper by H.J. Mueller? He used x-rays to make Drosophila fruit flies. sterile in 1928. That's when the paper was was published. And Mueller had actually been awarded the Nobel Prize in Physiology or Medicine in 1946 for what he had shown in that paper, that mutations can be induced by X-rays. And this, of course, alerted the public to the dangers of radiation and was part of the whole, like, oh, God, you know.
46:06 Speaker 00 Oh, no. Right.
46:07 Speaker 03 But when Nipling read this paper, he was like, oh, my God, this is it. This is what I've been looking for.
46:12 Speaker 00 Right.
46:13 Speaker 03 You know, I mean, paraphrasing.
46:14 Speaker 00 Can I do this with my flies?
46:15 Speaker 03 Yeah. And so he reached out to Mueller to be like, hey, do you think that I could use X-rays to make screw worm sterile? And Mueller was like, sure. Like, I think that sounds great.
46:24 Speaker 00 I'm at it, bro.
46:25 Speaker 03 Yeah. And so Nipling borrowed an army hospital X-ray unit to give it a go. And it worked. Like, not only were the males sterile, but the females that mated with them were also effectively made sterile because, again, they only reproduce once. And later, they switched from X-rays to, like, other methods of radiation, which gave more consistent results. But, you know, once they tested this out in the lab, all they had left to do was actually, you know, see if it worked in real-world settings. And the first trials were carried out beginning in 1951 on Sanibel Island in Florida. And when it was 200 to 300 sterile flies were released each week. How did they get so many flies, you might ask? They had to rear them in the lab.
47:10 Speaker 03 And because these live on, you know, like flesh, they used ground meat and blood. Can you imagine just like the smell of that rearing facility?
47:19 Speaker 00 I read several papers where people were talking about the smell and like the process of finding the right... Actually, I read a really interesting one about the lures that they use now, like when in their monitoring programs. They have a loom. The lure is called Swarm Lure. I think we're on version four. And it's like this concoction that they made based on looking at what are all of the scents and the things that are emitted by the meats and the blood and the oviposition fluid and all of this other stuff to try and make a lure to attract them. And it's like, wow.
47:50 Speaker 03 It's so gross. I love that, though.
47:52 Speaker 00 I know. Yeah.
47:53 Speaker 03 I mean, that like, I don't, that seems to me like complete alchemy. Like, that's magic, to be able to be like, what are these compounds? Let's make this.
48:01 Speaker 00 There was so many people at U of I doing stuff like that, but for agricultural pests.
48:05 Speaker 03 Agricultural, yeah, yeah. It was just, it all sounds, it all is amazing to me.
48:09 Speaker 00 I love it. Yeah.
48:11 Speaker 03 But anyway, so with the Sanniball Island, you know, real world experiment, the screw worm fly populations did drop over a couple of years, but they weren't eradicated. I mean, and they dropped dramatically, but they weren't eradicated entirely. And that's probably because fertile female flies flew over from the mainland. But like, and what they really needed, I think, what the US government was looking for outside of the USDA, but like, you know, the people who were providing the funding were like, we need 100% perfect eradication.
48:41 Speaker 00 It must be eradicated.
48:43 Speaker 03 Right, yeah.
48:44 Speaker 00 This is a war.
48:46 Speaker 03 This, yeah. And so they were like, we gotta do something else. Like, what else? What else? But this, so there was a kind of a lukewarm reception to these results. And so the US government wasn't really keen on continuing trials. They were like, we tried it, but I'm not sure. But then, there was an agricultural officer on the Dutch-controlled island of Curacao who reached out to Nipling for help with their screw worm problem, which was huge. In 1954, Nipling was like, let's do this. So they dropped more sterile flies on to Curacao, and screw worms were eradicated within 14 weeks, which is four to five generations.
49:26 Speaker 00 14 weeks?
49:28 Speaker 03 Yeah.
49:29 Speaker 00 Eradicated.
49:30 Speaker 03 Eradicated.
49:31 Speaker 00 Wow, I didn't realize it was that fast. That's bananas.
49:34 Speaker 03 Fast. And so this, finally, this was like, proof positive that Nipling's idea could work. And so the US government was like, okay.
49:42 Speaker 00 Okay, fine, bro.
49:43 Speaker 03 I guess. And the dream of actual widespread screw worm eradication got a whole lot closer to reality. And it demonstrated that you could effectively control agricultural pests without the use of toxic substances like DDT. And actually, in the, like, one of the last chapters of Silent Spring, Rachel Carson wrote about Nipling's work as like a hopeful path for the future. Like, we can use biocontrol in a way that doesn't, like,
50:12 Speaker 00 Destroy the environment.
50:14 Speaker 03 Yeah. Wow. It's very interesting. And so, construction on bigger fly rearing facilities began, including one that was capable of producing 200 million flies a week, which was a feat that required 120 tons of meat, 114,000 liters of water, and 38,000 liters of blood each week. Would you like to know what kind of meat? I really got into the rabbit hole here. Okay. It included horse meat, whale meat, and ground up nutria. Sorry. Yeah. Whale meat? Listen, I don't know. Later on, I don't think that this, I think that they were like, this is not sustainable. We need to do something else.
50:59 Speaker 03 And so, they developed like a gelled substrate that was like dried cow blood, egg, milk substitute, and some formaldehyde to prevent it from spoiling. So, they found something else that was less... Not using whale meat? Yeah. And so, after they constructed these fly rearing facilities, they were like, let's get this going. And so, in the early 1960s, an eradication program began that targeted the entire southwestern US. By this point in time, screw worm had been eradicated from Florida by the late 1950s. Okay. And so, over that decade, over the 1960s, screw worm populations plummeted. Erin, if you will, play the clip titled Screw Worm 3. Okay.
51:44 Speaker 05 In this half of our century, man has conquered the atom, the frontiers of space, the depths of the ocean. Could not this advanced technology be applied to control pests with even greater effectiveness and safety? Within the last decade, radioactive cobalt-60 has been used to sterilize millions of pupae of the male screw worm fly, whose parasitic larvae breeding in the flesh of cattle, deer, and other animals posed a major problem to our livestock industry in the southern half of the nation.
52:33 Speaker 05 Once the pupae developed, huge numbers of sterile male flies were dropped over infested areas to mate with female flies, soon drastically reducing the population of a major threat in America.
52:48 Speaker 00 So that was them doing the irradiation, right?
52:58 Speaker 03 Yep, yeah, that was them dropping, yeah, so that that video is from the same clip from that I played at the start of this, from 1969 clip. And despite the haunting music, like, the narration ends quite optimistically, right? Like, this is the end of screw worms. We're starting to see, like, we are conquering this.
53:19 Speaker 00 Right.
53:20 Speaker 03 By the way, the video, I don't know if I mentioned this, but the video is titled, "Who Shall Reap"? Yeah, it's kind of, anyway, the whole video is great.
53:30 Speaker 00 It's so, this is a total side note, but it's so interesting to watch these old videos that are so, like, slow.
53:38 Speaker 03 Oh, yeah.
53:39 Speaker 00 And the way that they're like, "The narration is like this." And then, like, even the clips of everything, and I'm like, if this was today, it would be like, "Screw worm."
53:48 Speaker 03 1,000 cuts, like...
53:51 Speaker 00 A million cuts, yeah. You'd never actually see a fly, because it would just be like, "Bloop, bloop, bloop." Anyways.
53:59 Speaker 03 Education by a million cuts, it's true. But, yeah, so, but this, I feel like the optimistic ending from that clip did play out for a while. Like, that is the way that it was, it was looking, at least in the southwestern US. But the feeling was unfortunately short-lived. Because outbreaks of screw worm began popping up in 1972 to 1976, and then 1978 as well. And, you know, what was going on? Part of it was suitable conditions for screw worm development, so like, it was a period of warmer and wet weather that provided just more habitat. And then, another was reduced care for livestock, so like, fewer and less frequent inspections once you think screw worms are gone.
54:42 Speaker 00 Right.
54:42 Speaker 03 One gets through, that one starts a huge problem.
54:46 Speaker 00 You're not checking as much.
54:47 Speaker 03 Yeah, but these were, I think, relatively minor factors compared to the real reason for these outbreaks, and that is that parasites don't respect arbitrary political boundaries.
54:58 Speaker 00 No, they don't.
54:59 Speaker 03 They don't. And so the eradication program, successful as they were, only focused on the US side of the border with Mexico, and since these flies can travel up to 180 miles or 290 kilometers, fertile flies could easily travel to treated areas. That's a hu- a huge flight range. It's wild.
55:20 Speaker 00 It's such a huge flight range.
55:21 Speaker 03 Yeah. And the, so the, the flight range, though, of these, of these flies was not known when they started the eradication program. I think this was like, one of the lessons learned right away.
55:31 Speaker 00 Yeah.
55:32 Speaker 03 And so after the first of these bad outbreaks in 1972, uh, which there was 95,000 cases were recorded, I'm sure that it was actually higher than that, um, the two governments, the US and Mexico, signed the Mexico-United States Screwworm Eradication Agreement. And about 10 years and a giant fly rearing facility later, capable of producing 500 million sterile flies per week, unbelievable.
55:59 Speaker 00 I mean, it's, the numbers are unfathomable.
56:01 Speaker 03 Truly, truly. Uh, but things started to look pretty good. Things were looking actually pretty great. And by 1991, all of the US and Mexico were declared free of screw worm. And there was a scary blip from like 1988 to 1992, when infected cattle were brought into Libya, in fact, infested with the New World Screwworm. And then that made people super concerned that like, hey, this is gonna take over. Like, this is going to spread everywhere, Africa, Middle East, Europe. And so a bunch of sterile flies were released, and by June 1992, the region was declared screw worm free.
56:36 Speaker 00 Yeah.
56:36 Speaker 03 And this really demonstrated the importance of, well, first of all, it demonstrated the power of the sterile fly, the sterile insect technique.
56:44 Speaker 00 Right.
56:44 Speaker 03 And the importance of thoroughly inspecting livestock for possible sides of infection. But that can be difficult to do. But do you know who's really good at it? Dogs.
56:55 Speaker 00 Dogs.
56:56 Speaker 03 Yeah. There are dogs that have been trained for this purpose today. And I think the first screw worm detection dog was, there's a paper. His name was Casador, which means hunter. And he was trained by researcher John Welch to work at quarantine and inspection stations. And he had a success rate of 99.7%. And the only time that he like didn't identify is when he had like some GI bug. And so he was sick and needed to rest.
57:22 Speaker 00 Oh, they made him work even though he was sick.
57:26 Speaker 03 I don't think they realized, yeah. But it's like, it's so sweet. The paper, I have it, it'll be on our, in our show notes or like in our, in our, on our website. And it's, he's thanked in the acknowledgements.
57:38 Speaker 00 Oh, my God, that's so cute.
57:40 Speaker 03 It is. And his leash and his ashes are in the National Agricultural Library in the screw worm unit.
57:46 Speaker 00 Wow.
57:47 Speaker 03 I know. Anyway.
57:49 Speaker 00 That's really special.
57:50 Speaker 03 Isn't that, I just loved that. We'll put a picture of cat, we'll try to find a picture of Kaz somewhere. There are lots of them, but. So anyway, over the 1990s and into the 2000s, eradication efforts in the Western Hemisphere continued into Central America and the Caribbean. And they were largely successful, at least for a time. But eradication has proved to be a moving target. And screw worm has reemerged in areas where it was previously declared eradicated. And in light of that, I want to play just one more clip for you. So play screw worm four.
58:28 Speaker 06 What lesson can we learn from the screw worm program? Well, to me, it's, it is a remarkable program. And I sometimes wonder how it ever materialized in the first place. And how they, they were able to get this program underway. But it confirms something that I'm absolutely confident of. And this is that if we're going to deal with major insect pest problems, we're going to have to deal with the, from an area-wide standpoint.
59:13 Speaker 06 That we cannot deal with these pest problems by just trying to control them year after year on a farm by farm basis, just like we never would have controlled the screw worm that way. We will never control the bow weevil or the corn earworm or the cabbage looper or coddling moth or whatever. You'll never control these insects this way. I mean, you'll control them, but you will not reduce the threat. But there is a possibility that we can do the same thing for dozens of other insects.
59:56 Speaker 00 Oh, Erin, I love that because that's like the conclusion at the end of my section as well.
1:00:02 Speaker 03 I know. Like, it just, so like I said, that interview was recorded in January 2000, and the lesson is as relevant today as it was then.
1:00:12 Speaker 00 And extends so far beyond just insect and agricultural pests.
1:00:16 Speaker 03 Yes.
1:00:17 Speaker 00 Dr. Nigling, thank you.
1:00:19 Speaker 03 It's public health. Yeah, yeah, like global, yeah, global health, all of that.
1:00:23 Speaker 00 Yeah.
1:00:24 Speaker 03 And so, yeah, with that, Erin, I'll turn it over to you to tell me where, what the people really want to hear, which is where we are with screw worm today.
1:00:33 Speaker 00 Oh, let me tell you, it's not great.
1:00:38 Speaker 03 Yep, yeah.
1:01:06 Speaker 00 Every week, still to this day, for decades now, planes drop millions of sterilized insects, which are grown and irradiated, they use slightly different techniques now, in a lab in Panama. They've moved. The labs are no longer, the rearing facilities are no longer in the US, no longer in Mexico, they are in Panama. And millions of sterilized insects are dropped across the Darien Gap and the very first part of Colombia in an attempt to keep screw worms out of Central and North America.
1:01:45 Speaker 00 And yet, despite all the success that you talked about, Erin, in 2016, I think is when the first like rumblings that things were not all perfect began in modern, most modern times, because there was an outbreak in Key West, Florida.
1:02:02 Speaker 03 That's right.
1:02:03 Speaker 00 It was relatively quickly contained, but the deer population in Florida took a hit because of this. And despite the incredible successes of the program, the truth is that new world screw worms are still present. This fly is still present throughout nearly all of South America, as well as many islands in the Caribbean, including Cuba, Haiti, and the Dominican Republic. And so since 2023, so in the last two years, cases have increased within like North and Central America from an average of about 25 cases per year to 6,500 in one year in 2023.
1:02:46 Speaker 03 Okay.
1:02:47 Speaker 00 And so since 2023, flies have been reported in Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Mexico, with more than 20,000 new outbreaks reported, like individual outbreaks, as of August 22, 2025, per the World Organization of Animal Health, or the WHO.
1:03:08 Speaker 03 Okay.
1:03:09 Speaker 00 Most all of these outbreaks are in livestock animals. There are some cases in domestic animals. There have also been cases in humans. But some of these outbreaks have been hundreds, if not thousands, of animals infected. So right now, on the AFIS website, which is the Animal and Plant Health Inspection Service. As of September 2nd, 2025, there are several outbreaks ongoing in Mexico that are of serious concern to the US government, which has resulted in the US government shutting
1:03:47 Speaker 00 down all live livestock, like live cattle trade between Mexico and the US. There have been over 5,500 total cases in Mexico. Currently, as of September 2nd, 777 active cases. And at least one confirmed case in a human in the US, which was a travel-associated case with someone traveling from El Salvador and coming back with an infection. They've recovered. In 2024, in Costa Rica, there were seven human cases that were reported, including
1:04:25 Speaker 00 one death. And in Nicaragua, there were 124 cases in humans in the last year. But this is not the case that like we as humans need to start panicking that we're all going to be infected with screw worm. That's not, that's not the situation here. But what this does show us is the fragility of our eradication efforts and the necessity of these one health approaches and that they don't face the kind of budgetary cuts that we see currently playing out across every single health agency in the US.
1:04:58 Speaker 03 Budgetary and like intellectual cuts.
1:05:01 Speaker 00 Yes.
1:05:02 Speaker 03 Drained.
1:05:03 Speaker 00 100%.
1:05:04 Speaker 03 I have a question about, so you, in terms of the numbers, we've talked about humans, we've talked about livestock, maybe a little bit of like domestic animals. What about wildlife?
1:05:17 Speaker 00 Great question. What about wildlife? Certainly, some of these infections are happening in wildlife, but we just don't have as good of numbers on wildlife populations. But, but that is definitely a huge concern, right? Because not only is that like a potential reservoir, but it's also just then we're affecting livestock populations. And like the effects of this eradication program on benefiting the health of wildlife should not be understated as well, too.
1:05:40 Speaker 03 Yeah.
1:05:41 Speaker 00 Yeah. So that's kind of like where we stand with like what's going on with current, with current outbreaks. The live cattle market in the US was valued in 2023 at $3 billion per year.
1:05:58 Speaker 03 Okay.
1:05:59 Speaker 00 And it's gone up since then.
1:06:02 Speaker 00 And the USDA says, estimates currently, that an outbreak, like a true outbreak of screw worm in the US could end up costing something like $10 billion in losses.
1:06:16 Speaker 03 So this is, this is something that I kept coming across too, was the screw worm eradication program, which has cost money.
1:06:23 Speaker 00 Cost money. It costs a few million dollars a year.
1:06:25 Speaker 03 Yeah, it has saved so much in terms of revenue from livestock, people's livelihoods. And I think what is like, it's like, okay, well, we can do this. We did this here in the US. We did this in Mexico. We did this throughout a lot of Central America. And in South America, it's like, well, they couldn't afford these programs, but they are losing money year after year. And so it's like, again, it comes back to this has, this is an area wide program. I lack the words, the articulation needed to express this, but like, this should be a continental, hemisphere wide effort.
1:07:03 Speaker 00 A hundred percent, Erin. And so right now, what the US is doing is going absolute ham. They are reopening facilities in Texas. They are rebuilding a facility in Mexico. They're going to spend tens of millions of more dollars to start breeding flies in the US and Mexico for sterile insect technique. It is going to take years, at least 18 months is the current estimate, for these to happen and get up and running. This is essential that it happens right now. And they have this like five point plan, which all sounds very much like war language. But they are taking this very seriously. And I think there was a paper from 2000, actually, that really exemplified what is
1:07:45 Speaker 00 the true kind of hero of the screw worm story. And that is that in order for the success that we have had thus far to happen, a ton of cooperative agreements had to exist between countries for this eradication program to take place and to be successful. Because yeah, flies don't give a crap about our national borders, the same way that infectious diseases like COVID don't honor these artificial divisions.
1:08:15 Speaker 03 Right.
1:08:17 Speaker 00 Even though this program is currently kind of at risk, right? And we're having to re-up it. It was only possible in the first place because countries decided it was important enough to invest in and to work together despite the difficulties and the like financial agreements that had to be made to coordinate the implementation of this program. But they agreed it was important because they could make a lot more money.
1:08:47 Speaker 03 I mean, yeah.
1:08:48 Speaker 00 And because the livestock industry.
1:08:50 Speaker 03 Money saving, yeah.
1:08:50 Speaker 00 Yeah, the livestock industry and the funding around this were considered important enough. The absence of these screw worms in the US is estimated at least at a minimum to be a $1.3 billion benefit every single year. So spending a few million dollars to keep this program running is nothing compared to that benefit.
1:09:15 Speaker 03 Yeah.
1:09:16 Speaker 00 It would be great if we could recognize that this is also true for so many other things besides just screw worm. And yes, expanding this to be able to eradicate it throughout its entire range rather than just stopping at the border of Colombia would go a really long way to improving the lives of humans and livestock and wildlife across the entire Western Hemisphere.
1:09:41 Speaker 03 Yep.
1:09:43 Speaker 00 Uh huh. And it is also possible that this could happen for old world screw worm. They have very similar mating habits, so they could also benefit from sterile insect technique programs. But there just hasn't been as much of this collective agreement, infrastructure buildup, and the money upfront to be able to do this where old world screw worm, that's really hard for me to say, is endemic. And so the programs that have tried to get up and running there have not been as successful. There's a lot of interest too in like creating like newer techniques to make this even more effective and even more cost-saving, like doing transgenic flies so that you're only really rearing male flies.
1:10:25 Speaker 00 Because right now you're rearing indiscriminately female and male flies. So if you could kind of whittle down the female population so that you're only releasing male flies, you're kind of doubling your efforts but at a lower cost. But like all of that is amazing. This is an amazing program. It is incredible. Let us apply this success to other facets of public health.
1:10:49 Speaker 03 Use it as a framework like this is, I mean, and it is like it's.
1:10:53 Speaker 00 It is, but it's also not.
1:10:56 Speaker 03 Yeah.
1:10:57 Speaker 00 And that's screw worm, baby.
1:11:06 Speaker 03 Oh, wow.
1:11:09 Speaker 00 What a, what a fascinating thing, though, like also just the like this, the, the entomology of it all. I love.
1:11:16 Speaker 03 The entomology, I just also, I love, I think this is when I was like, oh, I could spend weeks just digging around on the USDA, like the, the National Agricultural Library website. And then the archives, the internet archive, like I was having a blast looking through these oral histories and the transcripts. And I'm like, there are more that aren't digitized. I want them. I reached out to a librarian and was like, can you help me find this? And they did. And I'm just like, I love library. I love libraries. I love librarians. It's, and also I, I think I had no concept how huge this program was because you, you can't find a lot of other agricultural, well, maybe agricultural pest videos,
1:11:58 Speaker 03 but like other disease videos from the 1950s and 60s and so on, not so much. Like this is a huge effort and it was a huge success story and it can still be.
1:12:10 Speaker 00 Yeah, it will be. I think it will be successful. The funding is going there. It's happening.
1:12:16 Speaker 03 Yeah.
1:12:16 Speaker 00 But yeah, can it go further? That would be cool.
1:12:19 Speaker 03 That'd be cool. Should we tell the people where they can find more information?
1:12:23 Speaker 00 We should. We should.
1:12:26 Speaker 03 I have linked to all of those videos.
1:12:30 Speaker 00 Love it.
1:12:30 Speaker 03 I have a ton of sources, but I'm going to shout out two in particular. So one was the, the website, the screw, the Stop Screwworms. It's a, it's an online like digital collection. So it's selections from the Screwworm Eradication Collection on the National Agricultural Library USDA website. It's very cool. And then also there was a fun, a couple of fun chapters in a book, a popular book published in 1984 called The Dragon Hunters by F. Graham. And it was, uh, these two chapters that I read focused on a screw worm and screw worm eradication.
1:13:06 Speaker 00 Love it. I had a bunch of papers. I don't even know, Erin. The one that I mentioned already that I did really enjoy was by WIS from 2000 called Screwworm Eradication in the Americas. That focused a lot on like the success of these collective agreements and things like that. There was also a paper from 2017 that was review of research advances in the screw worm eradication program over the past 25 years. That was really interesting. And then a couple of papers that are like quite old from like the 80s and 90s about the screw worm behavior and biology and things like that. And then I also have links to the USDA website where they have their New
1:13:48 Speaker 00 World Screwworm Domestic Readiness and Response Policy Initiative document, which is really interesting to read through. And then also the updates, if you would like them, because I'm sure the numbers will be different by the time that this episode comes out. But on the AFIS website, you can find those like updated data on what the outbreaks look like in Mexico, what other cases have been reported and things like that. You can find it all on our website, thispodcastwillkillyou.com.
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1:14:44 Speaker 03 Until next time, wash your hands.
1:14:46 Speaker 00 You filthy animals.
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