Morgan O'Hanlon 00:00

You're listening to Season Two of Better Outside, a Texas Parks and Wildlife production. This season of Better Outside is brought to you by Minn Kota and Humminbird. Humminbird delivers intuitive fish finders that give you a clear, detailed view of what's below, so you spend less time managing technology and more time fishing, you I'm your host Morgan O'Hanlon,

David Yoskowitz 00:25

and I'm David Yoskowitz, Executive Director of the Texas Parks and Wildlife Department.

Morgan O'Hanlon 00:30

This episode is a buzz with flies, and one fly in particular, the New World screwworm fly.

David Yoskowitz 00:37

That does not sound very good.

Morgan O'Hanlon 00:39

They definitely aren't, and you're going to learn lots more about that right after this break. Minn Kota built to fish, and Humminbird making every cast count simply clearly better. When you hear a Humminbird fish finder with a Minn Kota trolling motor, you'll look like a fully connected fishing system designed to make every minute on the water count. David, how much do you know about the new world screwworm fly?

David Yoskowitz 01:14

Much more than I'd like to.

Morgan O'Hanlon 01:15

Why don't you start by telling me why they're called New World screwworms? Is there an Old World screworm.

David Yoskowitz 01:21

Well, Morgan, actually there is. It's the new world, being really the Western Hemisphere. So, in Asia and parts of Africa and the Middle East, the Old World screwworm exists. All screwworm flies are known for having a pretty nasty diet as maggots. They feed on the flesh of living organisms,

Morgan O'Hanlon 01:42

that's absolutely disgusting, and I guess I still am not 100% certain as to why we're talking about them. I'm a lifelong Texan, and I thought I would have already heard about something so scary already living in the state of Texas.

David Yoskowitz 01:58

Well, over the last several months, they've been making their way up from southern Mexico to our southern border, and right near Texas, and so it's been of great concern to not only the department here but also those that have livestock and companion animals as well.

Morgan O'Hanlon 02:18

So this is all relatively recent.

David Yoskowitz 02:20

Yeah, I mean, the new world screwworm has been around for quite a while, but it's been taken care of and pushed back down to where it was endemic in Central America and the northern part of South America.

Morgan O'Hanlon 02:35

Well, then, David, I can't say I'm so excited, but I guess it's time to go outside now and learn some more.

David Yoskowitz 02:44

Let's go outside, you.

Morgan O'Hanlon 03:15

To learn more about the new world screwworm, I called Dr. Sara Wyckoff. You might remember her from our Big Horn episode in season one. I'm Dr. Sara Wyckoff, and I am one of the wildlife veterinarians for Texas Parks and Wildlife Department. And Dr. Wyckoff, what is the new world screwworm?

Dr. Sara Wyckoff 03:32

So New World screwworm is the name of a fly, and the fly, the scientific name is Cochliomyia hominivorax, which, hominivorax actually means man eater, so that's kind of a little bit of a spoiler alert for what we'll be talking about with this fly, but this fly looks like your average house fly or a kind of blow fly, those metallic flies that you see that are maybe around like cattle manure or rotten food, but what's different about the new world screw worm is that instead of feeding on kind of decaying food or decaying flesh, the maggots of the fly feed on the living tissue of that animal, and that's how those maggots grow bigger, and then they pupate, and then they turn back into the adult fly, it only feeds on living tissue, any warm-blooded animal, including birds, but mostly mammals, but then also the name screwworm comes from the larva, kind of digging down, screwing into the living tissue to feed more and more as they get bigger,

Morgan O'Hanlon 04:40

yeah, that is just awful and terrifying. Do you know, is that supposed to hurt for screw worms to be inside of a living being?

Dr. Sara Wyckoff 04:50

So, screwworms, they're said to have very kind of sharp mouth hooks, which allow them to kind of burrow into the skin better. I imagine that it probably isn't. Very comfortable, just the feeling of something kind of worming its way down, but also with these wounds, you know, they start off as maybe something as small as a tick bite. The female fly will lay her eggs around that wound. Those eggs hatch into larva or maggots, and those maggots are what kind of burrow down, and they can make that wound very, very big, and very, very deep, and that significant wound, you know, if left untreated, can kill an animal.

Morgan O'Hanlon 05:27

Can you take us back in time? What would it have been like to live with the screwworm in Texas? Paint that picture for us.

Dr. Sara Wyckoff 05:34

Living with screwworm, it does sound like it was very harrowing. It was, unfortunately, a very important reason for economic loss. Back in the day, when it came to kind of the meat market, there was a lot of kind of extra work that had to happen to make sure that the animals on the farm were were safe, and that they weren't getting any, you know, screwworm kind of set up in any of their wounds, causing significant wounds in those animals, or even kind of the calves as well. Although I've been talking about how screwworm likes to lay eggs on wounds, they can also lay eggs on kind of exposed living tissue, like mucous membrane, so eyes, ears, nose, mouth, and umbilical stumps and calves, and so a really important part of being on the farm back then was making sure that calves and those umbilical stumps were protected, so screwworm couldn't get in there, and so back during that time it's estimated that, you know, hundreds of 1000s to a couple of millions of dollars of economic loss were the product of screwworm and livestock back in the day.

Morgan O'Hanlon 06:45

The new world screwworm is not native to the United States, but it was first documented here as early as the mid 1800s It was a significant problem in the US in the 1930s through the early 60s. This PSA from 1960 talks about the history of the screwworm infestation.

Speaker 1 07:02

Stockmen have been fighting this pest for more than 100 years. The first screwworms to reach the southeast were traced to incoming shipments of infested cattle in 1933 Within a year, infestations broke out in 30 Georgia counties and 20 in Florida they spread rapidly. By 1934 they reached as far as Lake Okeechobee. The next year they were found all over the state. Florida's climate permitted survival through each succeeding winter. Thus the screwworm also infested other parts of the southeast during warm weather

Morgan O'Hanlon 07:41

in 1960 scientists discovered a solution that could help solve the screwworm problem

Dr. Sara Wyckoff 07:47

through something called sterile insect technique, and a bunch of collaboration between kind of federal partners and the agencies. The screwworm was able to be eradicated and pushed out of the United States back in 1966 there have been a couple of little reintroduction events since then, where a fly has kind of come in, or maybe a little population has come in, caused a little outbreak in the area, but then it was able to be successfully eradicated or pushed back, and right now the most recent outbreak that happened, kind of on United States soil, was an outbreak in 2016 in the Florida Keys, where it affected the Florida Key deer population out there, which is a threatened deer species.

Morgan O'Hanlon 08:32

You mentioned a sterilization process for these flies that was part of the solution of eradicating them. Can you go into that history a little bit. How did the sterilization program start, and what did it do?

Dr. Sara Wyckoff 08:45

Yeah, that's a great question. So, the sterile insect technique, or SIT, as you might see it, was kind of the collaboration of two different ideas coming together when it came to what can we do to tackle screwworm. One of them was looking at the biology of the animal or the insect in this case, and saying, what can we do to help interrupt this life cycle.

Morgan O'Hanlon 09:07

Here's another clip from 1960 when scientists were already working to answer that question. The

Speaker 1 09:13

Department of Agriculture has spent years searching for new and better ways to combat this destructive pest, an entomologist of the Agricultural Research Service proposed, if a method of sexually sterilizing flies could be found, eradication is probable.

Dr. Sara Wyckoff 09:35

With New World screwworm, the female only mates once in her entire life, and her lifespan can be 21 to 45 days, kind of depending on factors like weather and soil, and so when scientists were thinking about how to interrupt this cycle, they thought, what if we get some sterile males out there that the females will mate with, but then nothing happens because the males. Are sterile and so there's no egg production, and so releasing those flies into the population helped bring down numbers, because if you're mating, but then there's nothing coming out, then slowly over time the cycle can die.

Morgan O'Hanlon 10:14

But how did they sterilize the flies?

Speaker 1 10:18

Geneticists had accidentally sterilized fruit flies with x rays, so x rays were tried on screwworms, and they worked. Later, x rays were tried on screwworm pupae. Irradiation during this stage also made screwworm flies sterile. This was the first real breakthrough toward a new approach to insect eradication. The most significant step forward came when a much cheaper way was found to cause sterility, expose the screwworm fly to nuclear energy, cobalt 60 gamma rays,

Dr. Sara Wyckoff 10:54

so that was one part, but then the other part was the ability to mass produce these flies in research settings, without having to use live animals or living tissues or anything like that for feeding, and so they were able to create these flies with just a gross mixture of like liver juice and blood, and a little bit of formalin on top, and able to mass rear these flies, and able to pump out, you know, hundreds of millions of flies a week, which is fantastic.

Morgan O'Hanlon 11:24

It looks like that program was pretty effective, right? Like, they're not here anymore. Is that correct? Where were we able to push them back to? Because I know they're not gone entirely anymore, or else we wouldn't be here talking about this.

Dr. Sara Wyckoff 11:38

Yes, and it's very important to point out that the sterile insect technique is the mainstay of eradication when it comes to screwworm, you know, that's the important driver here in all of this, and then the second important part is going to be kind of boots on the ground, early detection, observation, and if you are, you know, a livestock producer, farmer, landowner, anything like that, making sure that your animals are treated and inspected appropriately, but as far as kind of what's going on in in modern times, so when the screwworm was eradicated from the US in 1966 it was pushed out of the US, pushed down through Mexico and past this natural border called the Darien Gap by Panama, and the flies were kind of down in their regular normal zone of South America, so they're endemic there, and this kind of natural gap, which included like water, a bunch of dense forests that the flies didn't really like that, and then kind of continuous releasing of sterile flies allowed screwworm to stay back in its endemic area and kind of away from Mexico and away from the US, but where we're at now is that natural barrier has reduced with habitat fragmentation and habitat reduction to where a lot of that land has turned into pasture land, and on pasture land, not only is there clearance of those dense forests, but cattle are on pasture land, and we've been talking about how much these flies love cattle, you know, it's just a big piece of meat, you know, essentially, and so that is why they make kind of a perfect setup for these flies, and so that, and also the legal and illegal transport of cattle up from South America into Mexico and the US has allowed this fly to kind of break past some of the previously set barriers and now move more northward than we have seen over the last decade since it's been eradicated.

Morgan O'Hanlon 13:38

Is this something that we need to be paying attention to somewhat urgently,

Dr. Sara Wyckoff 13:42

so this is something that is definitely on the radar, not only for Texas Parks and Wildlife, but also the Texas Animal Health Commission, our human health state service, as well, but also, you know, federally too. This is disease that has a lot of potential to, you know, affect food and public health, and of course, you know, we take that very seriously here in America, and we want to do everything we can to protect our food supply and our people as well. And so this is a disease that is certainly being monitored very aggressively. USDA has a website that shows where detections are being found in livestock and domestic animals in Mexico. We're sending USDA scientists and veterinarians down there to help out Mexico as well with their detections. Currently, as when we're doing this interview, of course, want to say screwworm has not been found in the US. It is still south of the US, with the closest current detections being in Tamaulipas, still about 200 miles away, but we're talking about a fly that in 2022 wasn't really on the radar for moving upward, and now in the last three or four years it's come up from South America through Central America and Mexico, so it has moved pretty quickly. Day over the last couple of years, the really great part about trying to make the best out of a situation, right, is everybody is all hands on deck for this, not only the state and federal agencies that I mentioned, but NGOs, universities, pretty much everyone who can try to do something, whether it's putting up game cameras somewhere, or providing some type of database, so people can report any type of concerns that they have, creating an inspection system, things like that. There are a lot of different people in a lot of different areas coming together to all work together to see what they can do to help prevent this from coming into the US to mitigate things not only for us but for other countries as well, and to work on an international level to get screwworm pushed back down into its natural and endemic areas, and you know, away from the US, but also Mexico and Central America,

Morgan O'Hanlon 16:02

when we come back from the break, Dr. Wyckoff gives us the big picture regarding screwworms and what we can do to help stop them. Pairing a Humminbird Explorer fish finder with a Mega Live Two Live sonar gives you a real time look at fish and structure. The Explore is the most intuitive interface on the water. Every unit features 1000s of industry leading lake master and post master maps, advanced sonar and imaging for best in class clarity and detail, and a bright, easy to read HD screen built for real fishing conditions. See underwater action with legendary Humminbird clarity, true to life detail, and a responsive picture. We're back with Dr. Sara Wyckoff, a Texas Parks and Wildlife veterinarian who's working to help prevent the spread of screwworms back into the United States. How is this affecting your day-to-day work?

Dr. Sara Wyckoff 17:08

Yeah, so we've been monitoring screwworm, oh gosh, at least a year and a half, I want to say now, you know, when the numbers kind of started to creep up through South America, and then when they started to get into Mexico, and so this has been something that's been on not only Texas Parks and Wildlife radar but Texas Animal Health Commission and the Department of State Health Services during that same timeframe too, we've been meeting weekly, biweekly with all of those agencies and our federal agencies as well, there's been a lot of discussions, webinars, meetings talking about how we can all unify as one front, and making sure that we're all on the same page, as far as responding, getting the information needed for appropriate epidemiological investigations, getting everything in line for our ag partners and our domestic animal partners, as far as treatments and preventatives, so this has been something that is for sure been, you know, every day worked with, and we've also established a new world screwworm task force within Texas with those agencies as well, where again this is something that we're working on every single day, is making sure that we have all of our ducks in a row and also making sure that we are doing what we can to keep screwworm out of not only Texas but the US as well.

Morgan O'Hanlon 18:27

I guess I'm wondering what the bigger picture is here. So, what if the screwworm comes back, is that going to have a big impact on Texans and Americans? And I guess, why are we talking about it from a TPWD perspective,

Dr. Sara Wyckoff 18:42

so screwworm coming back, it would create a really big ripple effect, and so while it might be easy to think, oh, it's just another fly, how bad good flies be, right? We have them all around us all the time anyway, and the issue with this fly is because it creates that ripple effect, it can cause a lot of damage, not only to the economy and to agriculture, but also wildlife, as well. Again, human health. This is a fly that can infest people, and so those larva, again, they like warm-blooded mammals, and we are warm-blooded mammals. And so this is something that we wouldn't have to think about for just cattle, and how could that potentially affect cattle production, raising cattle and the prices of beef, things like that, but we also have to think about our wildlife species as well. Deer are a perfect animal for screwworm, because they're a big animal, there's a lot of muscle and meat on them, and they move around a lot, so they can provide area for larva to kind of drop off and pupate and expand the range even more for screwworm. There are also some reports from documents back in the 30s where landowners report up to 80% of fawn crops and deer in their area failed, and some of that has contributed to what they think could have been screwworm, and some of the really, really bad. Infestation years, but unfortunately, at the same time, there's not a lot of historical data on how screwworm has affected wildlife, because it was so focused on, you know, livestock and food back then. So we really don't even know potentially how harmful this could be for a native species, but we also have to remember the human dimensions part of this, all people are used to seeing something that is unfortunately as graphic looking and as gory looking as New World screwworm, especially in their backyard. It's something that will be very, very difficult, I think, for some people to see and realize is out there, and I think that's kind of a bigger part of the larger effect that screwworm could have outside of everything physically that it could do is also just the effect on how people are seeing the nature around them.

Morgan O'Hanlon 20:52

Yeah, even as somebody who is outside a lot and reports on wildlife and the outdoors, I can't say I'm not just a little bit freaked out by this whole thing, and I imagine there's a lot of other people who are in the same boat. Should we be scared?

Dr. Sara Wyckoff 21:09

Well, the important thing is to not be scared, to not panic. It's very normal for us to be concerned, worried about something that we're unfamiliar with. Really, what we're telling a lot of people now is, you know, ask questions, ask your biologists about what you can do, what you can see, what they want you to do. If you have any concerns, you know, go to our website, Texas A and M Agrilife website, USDA websites. There's a lot of information and education on there about what is screwworm, what citizens and the general public can do when it comes to reporting any concerns for screwworm, protecting their livestock, their pets against screwworm as well, and then also making sure that you, you know, have a veterinarian that you can contact in case you do have any concerns for maybe finding screwworm on one of your animals, that's also going to be, you know, the same person who can come out, inspect and treat your, your cat, your dog, your cattle as well, and so that's going to be very important for people to know, is that this disease is very treatable, just have to, you know, be able to catch it early, catch it on time, and then also make sure you're doing things to prevent an infestation from coming back, so it is, when it comes to diseases, something that can be worked with, and has options, which is good. There's a lot of different steps and things that people can do to help educate themselves and to help themselves understand, you know, what their role in all of this is, because this is, you know, for everybody. We will be relying a lot on what people are seeing out there, what they're finding out there, and so I think just kind of pulling it back and just remembering that we're all in this together.

Morgan O'Hanlon 22:58

So, what do you think, David? Do you think I need to start worrying about the new world screwworm.

David Yoskowitz 23:02

I wouldn't say worry exactly, but like Dr. Wyckoff said, we just need to be aware and we need to be educated.

Morgan O'Hanlon 23:10

What can I and other Texans do to help?

David Yoskowitz 23:15

Well, I think if you see something, say something, report something. If you're a land owner and you see wildlife that is behaving differently, is confused, has open wounds on it. Unfortunately, you may see the maggots themselves on there, feeding on the flesh. Report that to us at Texas Parks and Wildlife on our website. We have a place for you to do that. To

Morgan O'Hanlon 23:39

report a suspected screwworm case. Call a Texas Animal Health Commission veterinarian on call at this number: 1-800-550-8242

David Yoskowitz 23:51

Reach out to your local county biologist. Also, that's an important contact point for you.

Morgan O'Hanlon 23:56

And we've already heard from Sarah about why TPWD is involved in this fight, but can you tell me a little more about the potential impact of New World screwworm on Texas wildlife?

David Yoskowitz 24:08

Yeah, as Sarah said in the episode, I mean it's could be critically impactful. We've had in the past when screwworm has been here in Texas significant impact on wildlife, especially newborn fawns, who are really susceptible in terms of white tail deer, but you think of all the warm-blooded species that are giving birth, and when they give birth, those little ones are really susceptible at that point. So we just need to be aware, we need to get on top of it, we have the expertise to be able to share with land owners, and also I really want to stress here, companion animals can be at risk as well. So those dogs and cats and other critters that we hold close, we also need to be looking out for them.

Morgan O'Hanlon 24:54

What else do you think we need to know about the new world screwworm?

David Yoskowitz 24:58

Well, I think it's important to know that. That your Texas state government is on top of it. The governor has established a response team that is led by both the Texas Animal Health Commission, the Texas Parks and Wildlife Department. It is made up of stakeholders that are in domestic livestock industry, that are part of other state agencies, that are wildlife stakeholders, veterinarians, etc. and that coordination is critical, and that is taking place at the state level. We're also working with the US Department of Agriculture, which is the lead federal agency, along with the US Fish and Wildlife Service Environmental Protection Agency. So those efforts are going on right now, and have been critically important to get us to the point where we can respond to this.

Morgan O'Hanlon 25:48

It sounds like there's already been a lot of work going on with new infrastructure in the valley to help support this effort.

David Yoskowitz 25:56

That's right, so there's two facilities that are critically important, and as was talked about in the episode, is that the way that this was been beaten back has been the use of the sterile fly, and so we have one facility that is now growing out pupa to be sterile flies and distributing those along the border, but then also right now there is a facility underway to grow out new sterile flies.

Morgan O'Hanlon 26:24

Here's a clip of US Secretary of Agriculture Brooke Rollin speaking at a ribbon cutting for that South Texas facility back in April.

Speaker 2 26:32

What a joy to be back in McAllen with all of you to talk once more about what we are doing to fight and win against the New World screwworm. Last August, we pledged to build a New World screwworm sterile fly production facility right here in the United States, which we have never had before. Once operational, this facility will initially produce an additional 100 million sterile flies per week in stage one, but eventually when we get to stage two, which will be the end of 2028 we'll be at 300 million sterile flies, as we say on the offensive and screw, or we will make sure that our other lines of defense continue to strengthen.

David Yoskowitz 27:16

So, Morgan, I think the important takeaway here is that there is a lot of effort, both at the federal level, the state level, multi-state level, working with Mexico as well to combat this, and the technology that we have available today, not only in addition to the sterile fly, but other technology that is being brought forward just because the advance in science since the 60s and 70s really brings a lot of hope that we could address this head on in a much more significant and impactful way than we had, you know, 50 years ago, you

Morgan O'Hanlon 28:13

You've been listening to Season Two of Better Outside, a Texas Parks and Wildlife production. This season is brought to you by Min Kota and Humminbird. This episode was written and recorded by me, Morgan O'Hanlon. Story edited by Wes Ferguson and Aislin Gaddis for Free Range Productions. Audio production and sound design by Austin Sisler at East Side Studios in Austin, Texas. Our theme song was written and recorded by Walker Lukins and Grant Epley. Artwork for the show is by Erin Zachary. You can find Better Outside on Apple Podcasts, Spotify, or head to Better outside.com where you can find show notes, photos, more great stories from the Texas outdoors. If you like Better Outside, you can find more work by me and other outdoors writers at TPW magazine.com that's Texas Polecat waco.com and you can support us by subscribing to the magazine for only $2 a month. That's all for this episode. See y'all next time, and thanks for joining us outside,