Ep 192 New World Screwworm: Oh-oh here they come

This is exactly right. People who didn't do what John F. Quad wanted them to do, they usually disappeared. John of God was once Brazil's most famous spiritual healer. But in this limited series podcast, we uncover the darker truth behind his global empire of faith and fear. From exactly right and a Thundermedia, this is Too Faced, John of God. Listen on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Stopping screw-arms is your concern, especially if you own livestock or a dog or cat or any other pet. All of you can help by finding and reporting screw-arm 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. 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. Positive identification will be made by experts and measures taken to eliminate the parasite. A screw-arm infestation confirmed by a positive identification sets off a series of emergency activities at screw-arm eradication headquarters at Mission, Texas. Here millions of screw-arm flies are being re-ed each day and made sexually sterile by exposure to gamma rays from radioactive cobalt. Released in special patterns and in large numbers, these laboratory re-ed flies fight for us against an outbreak. These sterile screw-arm flies mate with native flies which in turn cannot reproduce. Released of sterile flies combine with intensive livestock inspection and use of insecticidal treatments has already stemmed outbreaks. This new technique for insect control is eliminating screw-arms 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-arms. The next step is to make sure that the virus is safe and safe. The next step is to make sure that the virus is safe and safe. The next step is to make sure that the virus is safe and safe. That's the whole episode, isn't it not? Isn't that amazing? It's so comprehensive. Okay, so that was from... I found that on the USDA National Agricultural Library in like the screw-arm exhibit. It was a video produced in 1963 and it's called Look Out for Screw Worms. I think I didn't realize the extent to which screw-arm was such a big deal during that time period for decades and decades and decades. I have so that there are promotional videos like this. I'm really excited, Aaron, to hear you talk about the history because I was reading and didn't realize a lot of the history of ranching the US was driven by screw-arm. I know. I know. There's so much to cover. We'll get into all of it. I want to start right now, but we won't. We'll start instead with introductions. Hi, I'm Aaron Welsh. And I'm Aaron Omenupdate. This podcast will kill you. And today we're talking about screw worms. Specifically for me, I'm talking about new world screw worm. 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. The one that's been in the headlines. And news. And news. Big time. It's going to be a really interesting episode and a little bit maybe creepy crawly as only a little bit. A very creepy crawly. Yeah, some of the descriptions I have are hard to stomach. Okay, that's good. I don't have that many of those. Okay, okay. And keep it basic. But before we get into all of that, it is quarantine. Quarantine. Quarantine time. Yeah. What are we drinking this week? We're drinking the screw worm driver. Yeah. It was just a screw driver. Screw driver, which is vodka and orange juice. And with the addition of a gummy worm. Gummy worm to represent a worm. Screw worm. We're getting real creative with these Aaron. You know, I think that's okay. It's totally fine. Okay. It has to be. It has to be. We can do nothing else. Yeah. Yeah. We'll post the recipe on the places that you can find it. Like our website, thisPodcast.co.uk, someday. But also definitely on our socials, this podcast will kill you. What? Socials. 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. You know what? Listen. There's a way. There's a lot of other great stuff on our website. Yes, there is. We've got transcripts. We've got references for all of our episodes. So if you want to read more about Screw Worm, 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 first-hand account form. Patreon. Other things, probably. Check it out. There's a lot there. ThisPodcast.co.uk.com. If you haven't yet, rated or read and subscribe. Please do that. We'd really love it. We've got a lot of content on YouTube on the right network channel. And we're on all of your favorite pod catchers, including I Heart Radio Apple Podcasts Spotify, The Like. The Living On. Moving on. Are we done? Yeah. Should we? Great. Are you ready? Yeah. I am. I'm going to tell you about the biology of Screw Worm really fast so that you can tell me about the history. Okay. Okay. Let's take a quick break and then we'll get to it. The star of today's show is the Screw Worm, which is a larval form of a fly. Most people, when we say Screw Worm, mean the New World Screw Worm, which is the species Cochliomaya-Hom-Nivorax. Might have pronounced that wrong. Hom-Nivorax. Listen. It's the New World Screw Worm. But there is another one, the Old World Screw Worm, which is a species called Chrysoma-Beziana. Okay. And these are two different genera of fly, but both of them are blow flies. 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. Yeah. This may change our feelings on maggots, I think. It will. Because today we're talking about pretty much the exact opposite. Unlike most other species of blow fly, 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. The 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. Kind of like bot flies, but more harmful. Way more harmful. 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 cochleomia, hominivore acts 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. So interested in their evolutionary history, which I didn't look up like the relationship between them. But like independent, yeah, anyway, like I didn't look at it either, but that's really interesting. Yeah. How did they both end up evolving this way of life that's so different from all of their other brethren? Right. I mean, 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. Right. Exactly. And so the adult flies, all entomologists everywhere are going to kill me for saying this. They look like a fly. Okay. How big. How about a little bit larger than a horse, a house five. Okay. Not a horse five, house five. And they that's literally what they look like because they are blow flies. A lot of the house flies that we see, not house flies aren't necessarily blow flies, but you see these around. They've got almost like a metallic ish kind of bluish greenish body, like most blow flies do. They have these big giant orange-ish eyes across their heads. And then they have these three black and gray stripes along their back. The old world's groomroom has two of those stripes. Okay. The new world's groomrooms 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. The adult flies emerge from the soil where they pupate. 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. 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 people form. This flies lay 200 to 300 eggs. Some estimates say as much as 500 eggs per clutch. It keeps getting worse. Because they lay additional clutches every three to seven days for up to 11 clutches of two to 300 eggs in a lifetime. And we can air 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. I mean, that is some hard work. It really is. They also often leave each one of their clutches in several different egg masses. So not all like 201 spot, they'll lay them over, of course, of a few minutes or a couple of hours in multiple times. Don't put all your eggs in one lesion kind of a mentality. Exactly. 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. They want the freshest of flesh, the freshest of flesh, and they especially prefer wounds that have already been infested with screwworms, 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 mucus membranes. So say the corners of eyes or in noses, 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. Yeah. 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, screwworm. Their wriggly little maggot bodies are even grosser looking than most maggots. They have, it's not a thing that you can say. I mean, that is a high bar. Like maggots are disgusting looking. maggots are gross looking, 100%. But these ones have particularly sharp hooks on their mouthpieces. 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. Yep, yep, yep. Yeah. And that is what helps them literally corkscrew their way deep into the living tissues on which they're feeding. How big do these larvae get? 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. Okay. Okay. They can, yeah. 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. And once they emerge, okay. So I'm thinking about like going to in a place where screwworm 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? I'm like, right? It's not like a one time thing. I have no idea. It's like one week then do they overwinter, et cetera, that kind of stuff. Yeah. So I mean, they tend to live in the tropics. And in the tropics, they're, they're all year round, right? And so they're going to be continually and each female adult females live for about 20ish 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, a little more than a month. Okay. And so you could be getting 12 plus rounds. I mean, plus each female is laying like 3000. Yeah. I can't even calculate that's a lot. It's just hard to comprehend like, like they, I feel like they would run out of living tissue to eat. It's an interesting. So it's actually really interesting that you say that because one of the, one of the papers that I read was looking at like the, the, the Ova position behavior of these flies. And they were pointing out that like, if you look at the way that they overposs it 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. But the way that these particular screw flies do it, they at least in this paper were saying that this fits with this strategy of like exploitation where they might be evolutionarily. Being niches that aren't always there, right? In an environment that's not always favorable. And so you 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. Okay. Which suggests that in nature, the perfect wound Ova position site might have been harder to come by. But then enter livestock. And livestock, yeah. 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 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 Ova posit in to begin with can be as small as a tick bite and often are from a tick bite. 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. 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 from, you know, the open wound that is caused by these maggots. So that's like mostly screw worms, Erin. 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? It's a good question. It was like weirdly hard to find great papers on the old world screw worms. So from what I can tell, they don't tend to be maybe quite severe or at least not as deadly as quickly. Okay. Okay. I don't know exactly why, like what are, you know, all of the specific differences between them. 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. I see. Whereas we have changed the current distribution of the new world screw worm. Yeah. Against it will. 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 avarmectins like Ivermectin. So for humans, when there is human infection because there can be and there is, this is also a public health problem, not just a livestock problem. It requires oral Ivermectin and this doesn't like get rid, get rid of the infection per say. What it does is paralyze the larvae which then have to still be removed thereafter. Okay. It paralyzes the larvae. How interesting. Yeah. Yeah. Yeah. So our main stay of dealing with the new world screw worm has been sterile insect technique. It's so cool. Prevention. Tell me all about it. Is it my turn? It hurts really? Yeah, I don't have any more. Great. I'm going to be basic and straightforward. I'm excited. All right. Let's get started. People who didn't do what John F. Quad wanted them to do, they usually disappeared. John of God was once Brazil's most famous spiritual healer. But in this limited series podcast, we uncover the darker truth behind his global empire of faith and fear. From exactly right and a thundermedia, this is Too Faced, John of God. Listen on the iHeart Radio app, Apple podcasts, or wherever you get your podcasts. So to help me set the stage for the history of screw worm, I've brought along some assistance. Aaron, I can't wait. Please open the video titled Screw Worm 1. 300 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 soened ended. Did you like that? I loved it, Aaron. I really hated the grub. Those were grubs, not maggots. The video is like everything. Grubs, grubs, outtakes. That was clear. 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 USD at DA in 1969. And it goes into some of the various like insect and plant pests, including screw worm. Plagging farmers across the globe. I also thought that it was interesting because it was like one million species. And I looked it up and I think we're now at like 5.5 million species. I was like, that is such an underestimate. It's like Dr. Evil, like one million dollars. Like that's kind of what a reminder being. One million species. Yeah. But yeah, I went all in on video clips for this episode. I can't wait. I can't wait. It was an amazing archive work at the National Agriculture Library on the USDA website. And as well as the Internet Archive, which is just one of my favorite things in existence. 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 going to just be focusing pretty much only on New World Screw worm for this, which I'm just calling screw worm for short. That's what most of the literature does. That's why it was hard for me to find stuff on Old World Screw worm. Yeah. But it's a 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. Yeah. 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. 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. Interesting. Yeah. As human migration continued across North America and then down into Central and South America, this 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. It's like the reptiles. Yeah, yeah. Yeah. Yeah. Yeah. One flush. 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 mayiasis from screw worms is another matter entirely. It's not the same. It is not the same. I found a quote from CE 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. And quote. It's, I mean, it's truly awful. It is truly awful. Yeah. Yeah. And this feeling, this image, this sentiment towards my isis, this might have been what the guy who first described the new world screw worm was thinking when he gave it the name, the species name of how many Vorax, which is man eater. What it translates to. And so the guy who did this was named Charles Cocharell. He was a surgeon in the French Navy stationed at a penal colony, cayenne and 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. Yeah. Yeah. Naisal passages seem to be a really commonplace when there's human infestation. Mm-hmm. That makes sense. You just can't get at it. Right. Yeah. Well, and a lot of times, too, there's like, there's something else going on. Like you, like, you're in 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 swap flies away. That's that sort of a thing. But it's still, it's, it's, it's truly, it is truly awful. And I think that Cocharell himself was quite a bit taken back by what he saw. And he wrote in this description of treating this, these men that science is, quote, powerless to prevent these terrible ravages. And in that, he would ultimately be proven wrong, but it would take another hundred years or so for science to have a fighting chance. Mm-hmm. 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 a little helping it along. Overgrazing meant fewer prairie fires, so more continuously occupied habitat, more continuous host for the screw worm. And deer replaced antelope as the dominant game animal, which grew even more abundance. So like deer herds of course are like can be enormous. So that's like even more hosts for the flies. According to one researcher's observation from 1959, deer are often victim to repeat infestations leading to two to three thousand larvae in one wound. Oh goodness. And that amount of maggots, so two to three thousand, can destroy an area apparently seven inches wide and seven inches deep or 18 centimeters wide and deep. Seven inches deep. How many areas on a deer's body? Can you go seven inches deep without hitting some vital structure? I, I guess you, that's you can't. Yeah. I mean, wounds, wounds like these are can be deadly, our option deadly and in bad years, up to 80% of fawns of white tail deer were killed from these infestations. Oh, yeah. And these deer also provided ample hosts for ticks, specifically the Gulf Coast tick or Amelio immaculate them, 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 or a invested 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 or ameliezians 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 new newborn livestock are often infected at the navel. 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, ship it the meat. Oh, wow, Erin, put it all together. And what you have are the perfect conditions for for a screw worm storm. Just take over, just take absolute take over. 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. It sure wasn't a job for anyone with a queasy stomach. End quote. Oh, I've seen some pictures of that in like sheep's mouths and it's so awful, Erin. 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. 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. The horror of screw-room 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-room's biology, which was only corrected in 1933. So for decades, the screw-room 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 range land, that is going to prevent the screw-room from being a problem. But since it feeds exclusively on live flesh, it actually doesn't really do anything. And so recognizing that aspect of its biology was 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-room. And that was a newly minted entomologist joining the cause. In 1934, Edward F. Nippling, 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-room flies cotton traps. Nippling was no stranger to screw-room. He grew up on a farm in rural southern Texas. He was one of 10 kids, and the farm is how they produced most of the food for his big family. But they would all be, you know, take part in dealing with the livestock, and he described removing, having to remove and look out for screw-rooms, among other agricultural pests. Before he went to college, he was aware of screw-room 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. 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 the... revolutionary thing, kill it all. And also how quickly they lost their potency as insect-screw resistant, not to mention the toxic impacts of some of these pesticides. And so he realized that a different, more proactive approach was needed. Aaron, play the clip titled Screw Worm 2. Okay. This is so fun. Screw Worm 2. Well, we really need, in some way, to control the screw-rooms before they attack the animals. Rather than just waiting until after the animal has had the true arm, then try to control it. I realized that you would never, never really control the screw-rooms that way. What we needed was some preventive measure, but how to control the screw-room on hundreds of thousands of square miles of territory, of course, seemed like 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 rarer this screw-room and have it some genetic deficiency that it would release and release those genetically deficient insects in the population. They would mate with the normal flies and transmit detrimental characteristics. Just how I came to that conclusion, I really have a little difficulty even today. This is so amazing. He's like, I just kind of knew we had to do it. I don't know why I knew it, but I did. 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. I love that. So that was, yeah, that was that was Dr. Nippling himself interviewed in January 2000 as part of an oral history project for the screw-room education program. Yeah. Wow. And so what he's talking about here is what you mentioned, Aaron, 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. And the idea behind this is that the sterile males are released, 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, are in 10 to make just once. And so if they mate with a sterile male, there's no viable offspring. Yeah. And the females mate once, but the males mate, like up to 10 times. Yes. So one sterile male could be mating with 10 non sterile females and then they're not laying any eggs. Yeah. And then the second thing is that in the screw-room 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 reduce that population size to begin with. That actually makes a lot of sense. Yeah. And Nibbling 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, 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? Yeah. 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, like, alerted the public to the dangers of radiation and was like part of the whole like, oh god, you know. Oh no. Right. But when Nibbling read this paper, he was like, oh my god, this, this is it. This is what I've been looking for. Right. You know, I mean paraphrases. Okay, this is my class. 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. I'm not a bro. Yeah. And so Nibbling 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 made it 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 Sanabelle 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. And because these live on, you know, like flesh, they used ground meat and blood. Yeah. Imagine just like the smell of that. I feel like I read several papers where people were talking about the smell and like the process of finding the right. Actually, really 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 overposition fluid and all of this other stuff to try and make a lure to attract them. It's like a lot. It's so gross. I love that though. I know. Yeah. 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. There was so many people that you have I doing stuff like that, but for agricultural trail pass. Agri-culture. Yeah. Yeah. It was just, it all sound. It all is amazing to me. I love it. Yeah. But anyway, so with the Sanibel Island, you know, real world experiment, the screw worm fly populations did drop over a couple of years, but they weren't erratic. I mean, 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 the, you know, the people who were providing the funding were like, we need 100% perfect eradication. It must be eradicated. Right. Yeah. And so this is a new work. This, yeah. And so they were like, we got to do something else. Like, what else? What else? But yeah. 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 Kurosau, who reached out to Nippling for help with their screw worm problem, which was huge. In 1954, Nippling was like, let's do this. So they dropped more sterile flies onto Kurosau. And screw worms were eradicated within 14 weeks, which is four to five generations. 14 weeks? Yeah. Irradiated. Irradiated. Wow. I didn't realize it was that fast. That's bananas. Fast. And so this, finally, this was like proof positive that Nippling's idea could work. And so the US government was like, okay. Sure. Okay, fine. I guess. 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 Nippling's work as like a hopeful path for the future. Like we can use bio control in a way that doesn't like destroy the environment. 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 down the rabbit hole. Okay. It included horse meat, whale meat, and ground up nutria. Those were all 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. 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 the 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, and a eradication program began that targeted the entire southwestern US. By this point in time, the screw room had been eradicated from Florida by the late 1950s. Okay. And so over that decade, over the 1960s, screw room populations plummeted. Aaron, if you will, play the clip titled Screw Worm 3. Okay. 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. 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. So that was them doing the irradiation, right? Yeah, yeah. That was them dropping. Yeah, so that video is from the same clip 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 screws we're starting to see, like we are conquering this. By the way, 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. It's so, this is a total side note, but it's so interesting to watch these old videos that are so slow. Oh yeah. 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, we were like, one thousand cuts. A million cuts. You never actually see a fly because it would just be like, but anyways, 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 looking at least in the Southwestern US. But the feeling was unfortunately short-lived. Because outbreaks of screw-room began popping up in 1972 to 1976 and then 1978 as well. And what was going on? Part of it was suitable conditions for screw-room 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 of screw-rooms are gone. One gets through that one starts a huge problem. Yeah. You're not checking as much. 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. No, they don't. They don't. 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, photo flies could easily travel to treated areas. That's a huge flight range. It's wild. It's such a huge flight range. Yeah. So the flight range, though, of these flies was not known when they started the eradication program. I think this was like one of the lessons learned right away. Yeah. And so after the first of these bad outbreaks in 1972, which there was 95,000 cases were recorded, I'm sure that it was actually higher than that. The two governments, the US and Mexico, signed the Mexico United States Screw-Rome Eradication Agreement. And about 10 years and a giant fly-wearing facility later, capable of producing 500 million sterile flies per week. Unbelievable. I mean, the numbers are unfathomable. Truly, truly. 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's Screw-Rome. And then that made people super concerned that like, hey, this is going to 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. Yeah. And this really demonstrated the importance of, well, first of all, it demonstrated the power of the sterile fly, the sterile insect technique, 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. Dogs. 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. Oh, they made it work even though he was sick. I don't think they realized. Yeah. But it's like, it's so sweet. The paper, it'll be on our show notes or like in our website. And he's thanked in the acknowledgments. Oh, that's so cute. It is. And his leash and his ashes are in the National Agricultural Library in this screw-worm unit. Wow. No. Anyway. Isn't that, I just loved that. And we'll put a picture of cat. We'll try to find a picture of cats somewhere. Yeah. There are lots of them. 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 re-emerged 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 for. What lesson can we learn from the screw-worm program? Well, to me, it's a remarkable program. And I sometimes wondered how it ever materialized in the first place. And how they were able to get this problem 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, you know, from an area-wide standpoint. That we cannot deal with these pest problems by just trying to control them. Year after year on a farm or farm basis, just like we never would have controlled the screw-worm that way. We will never control the bowwee of the corn earworm or the cabbage looper or calling moth or whatever. You'll never control these insects this way. I mean, you control them, but you will not reduce the thread. But there is our possibility that we can do the same thing for dozens of other insects. Oh, Aaron, I love that because that's like the conclusion at the end of my session as well. Like I said, that interview was recorded in January 2000. And the lesson is as relevant today as it was then. So, it extends so far beyond just insect and agricultural pests. Yes, it's Dr. David Sinkia. It's public health. Yeah, like global health, all of that. And so, yeah, with that, Aaron, I turn it over to you to tell me what the people really want to hear, which is where we are with screw-worm today. Oh, let me tell you. It's not great. Yeah. Yeah. 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 Darian gap. And the very first part of Colombia. In an attempt to keep screw worms out of central and North America. And yet, despite all the success that you talked about, Aaron, in 2016, I think is when the first rumblings that things were not all perfect, began in most modern times, because there was an outbreak in Key West, Florida. That's right. 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. And so since 2023, flies have been reported in Belize, Costa Rica, El Salvador, Guatemala, Las Nicaragua, and Mexico with more than 20,000 new outbreaks reported, like individual outbreaks, as of August 22nd, 2025, per the world organization of animal health or the world. Okay. 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 A-Fist 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 down all 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 one death, and in Nicaragua, there were 124 cases in humans in the last year. But this is not the case that we as humans need to start panicking that we're all going to be infected with screwworm. 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. A budgetary and intellectual cuts. Yes, 100%. I have a question about, in terms of the numbers, we talked about humans, we've talked about livestock, maybe a little bit domestic animals, what about wildlife? 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 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 the effects of this eradication program on benefiting the health of wildlife should not be understated as well too. Yeah. Yeah, so that's kind of like where we stand with what's going on with current outbreaks. The live cattle market in the US was valued in 2023 at $3 billion per year. And it's gone up since then. And the USDA says that 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. So this is something that I kept coming across to was the screw worm eradication program, which has cost money. Cost money. It has to say $10 million a year. 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. A hundred percent. 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 the true kind of hero of the screwworm 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. Even though this program is currently kind of at risk and we're having to re-upped 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. I mean, and because the livestock industry. Yeah, the livestock industry and the funding around this were considered important enough. The absence of these screwworms 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. Yeah. It would be great if we could recognize that this is also true for so many other things besides just screwworm. 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. Yep. Uh-huh. And it is also possible that this could happen for old world old world screwworm. They have very similar meeting habits. So they could also benefit from sterile insect technique programs. But there just hasn't been as much of this collective agreement infrastructure build up and the money upfront to be able to do this where old world screwworm. 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 to 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 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 is amazing that this is an amazing program. It is incredible. Let us apply the success to other facets of public health. Use it as a framework like this is I mean, and it is like it's it is. But it's also not. Yeah. And that screwworm baby. Oh wow. What a what a fascinating thing though, like also just like the the entomology of it all I love 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 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 was like, can you help me find this and they did not just like I love library. I love libraries. I love librarians. It's and also I think I had no concept how huge this program was because you can't find a lot of other agricultural. I thought you know, maybe agricultural past videos, 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. Yeah. It will be I think it will be successful. The funding is going there. It's happening. Yeah. But yeah, can it go further? That would be cool. That would be cool. Should we tell the people where they can find more information? We should. We should. I have linked to all of those videos. I love it. I have a ton of sources, but I'm going to shout out to in particular. So one was the the website, the screw the stop screw worms. It's a it's an online like digital collection. So it's selections from the screw room 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 the dragon hunters by F Graham. And it was these two chapters that I read focused on a screw worm and screw worm eradication. Love it. I had a bunch of papers. I don't even know Aaron. The one that I mentioned already that I did really enjoy was by Whiss. From 2000 called screw worm 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 world screw worm 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 a fist 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. This podcast will kill you dot com. Thank you to bloodmobile for preventing the music for this episode and all of our episodes. Thank you to Leonna and Tom and Pete and Brent and Jessica and everyone else and exactly right who makes all of this possible. And to you listeners who also make this possible who you know let us keep doing this and our patrons, you know, a big. You know, thank you shout out to you as well. Your support means the world to us. We love you. Yeah. Well, until next time wash your hands. You filthy animals. You. You. You. You. You. You. You. You. You. You. You. You. You. You. You. You.