The Buzz on Flies of Importance with Sonja Swiger

For a large portion of the United States, the previous year has been one for the books. Plentiful rain and green grass - even in areas that usually can't claim anything green except for the bar ditches - are certainly caused for celebration. 

However, with that moisture comes its own unique set of challenges. Those challenges often materialize as nuisances that can cause tail swishing, bunching, overstimulated and stressed cattle. But there is a reemerging insect on the horizon that threatens to take the concern for fly control to another level. 

On this episode of Angus at Work, we are joined by Sonja Swiger, an entomologist with Texas A&M AgriLife Extension, to discuss: 

• The usual culprits,
• Why flies are an issue,
• How to control them, and 
• New World screwworm.

A huge thank you to Vermeer for their sponsorship of this episode. 

Additional Resources:

• AgriLife Extension New World screwworm fact sheet
• Texas A&M Veterinary Entomology resources
• Horn Flies and Grazing Cattle from the Angus Beef Bulletin EXTRA
• Choosing the Best Fly Control from the Angus Beef Bulletin EXTRA
• Subscribe to the Angus Beef Bulletin EXTRA

Find more information to make Angus work for you in the Angus Beef Bulletin and ABB EXTRA. Make sure you're subscribed! Sign up here to the print Angus Beef Bulletin and the digital Angus Beef Bulletin EXTRA. Have questions or comments? We'd love to hear from you! Contact our team at abbeditorial@angus.org.

Transcript

Lynsey McAnally (00:28):

Angus at Work, a podcast for the profit-minded cattleman. Brought to you by the Angus Beef Bulletin, we have news and information on health, nutrition, marketing, genetics and management. So let’s get to work, shall we?

 For a large portion of the U.S., the previous year has been one for the books. Plentiful rain and green grass — even in areas that usually can't claim anything green except for the bar ditches — are certainly cause for celebration. But with that moisture comes its own unique seat of challenges. Those challenges often materialize as nuisances that can cause tail swishing, bunching, overstimulated and stressed cattle. 

But there is a reemerging insect on the horizon that threatens to take the concern for fly control to another level. On this episode of Angus at Work, we are joined by Sonia Swiger, extension entomologist with Texas A&M AgriLife Extension to discuss the usual culprits, why they're an issue and how to control them before exploring the next potential threat: New World screwworm. So, let's dive in!

Vermeer Ad (01:22):

My name is Nick Jorgenson. I'm the CEO of Jorgenson Land & Cattle here in Ideal, South Dakota. When it comes to getting forages put up, the most important thing for us is getting it done as efficiently as possible. That's largely dictated by the equipment that you're using. 

So we've really focused on looking out in the industry and finding the best, most efficient equipment that we can find out there. But if you don't have equipment that's reliable and that runs well when you get it in the field and stays running, you're going to have a hard time. Vermeer products are a big reason that we can get more done in a day. See how Vermeer helps Angus producers do more at vermeer.com/angus.

Lynsey McAnally (01:54):

Welcome to Angus at Work. I'm your host, Lynsey McAnally, and today we're going to be discussing some particularly annoying winged pests. But first, Dr. Swiger, would you mind telling us a little bit about yourself, your role within the Texas A&M system and how you became president-elect of the Texas Mosquito Control Association?

Sonja Swiger (02:30):

Yeah, well thank you for having me here today! I am a livestock veterinary medical extension entomologist, which is a mouthful, but basically that equates to, I work in the field of extension for Texas a and m and go around discussing insects that bite on humans in animals, which of course led me to being a part of the Texas Mosquito Control Association. And after many years of being a member, I finally joined the board and next year I'll be the president. So I am currently the president-elect.

Lynsey McAnally (02:59):

Awesome. Well congratulations. That's a pretty cool title to have. So can you tell us a little bit about educating people on these biting insects and the importance of educating livestock producers in particular?

Sonja Swiger (03:14):

Yeah, I mean, obviously we're in the South. We have a lot of various insects of many types. My main concern, of course, is helping to protect our animals - and our humans as well - from both the bites and the pathogens that they carry. So with cattle, there's several different types of flies - mostly - that we're concerned with. And then you add ticks in there which technically aren't insects, but we kind of group them in as a local arthropod. And then also the chances of spreading diseases, which most of the time our flies aren't spreading diseases to our cattle, which is good, but there is potential out there. And we do all know that ticks definitely have a potential to carry pathogens of various sorts, and again, also for humans. So I play a big role in educating on mosquitoes and ticks for those folks. even fleas because there are pathogens they can carry.

Lynsey McAnally (04:06):

I had the pleasure of hearing your presentation at the 580 Cattle Conference in Woodward, Okla., and one of my favorite parts of that presentation were the slides that covered the different kinds of flies that we deal with in our part of the world. So do you mind giving us a little bit of an overview of those three, I believe, types of flies that you covered?

Sonja Swiger (04:25):

Yeah, I mean our three main flies that we generally deal with on a regular basis is usually how you term it. There's always a few others you can toss in there that show up from time to time. But [the three main types] are going to be the horn fly, which is one that's almost exclusively with cattle. They do have this close association because of the usage of their manure for growing their larvae, but they are a huge impact. They do cost the industry $2 billion just to manage them. And if you don't manage them, obviously you're going to have even more potential impact because there are constant biting species, both males and females or blood feeders, and they have to have that blood. Those are the ones you're going to see on the back and up on the head, and they do kind of, they're in large groups and look like a big cloud over the animal.

They're only able to hold a small amount of blood, so they take many blood males throughout the day. Another one is our stable fly as we refer to it. I have heard that called other things in the field. Stable fly is a species that does bite as well, both males and females, and they bite on the legs. They do prefer livestock so we do see them all the time with horses in addition to cattle. And they do have a $2 million impact to our cattle industry. [They are] generally found more in the dairy and confined barns, but they can still get out into the pastures. They are a really nasty biter that will also bite on humans and dogs and can have a major impact.

Lynsey McAnally (05:52):

Are those going to be the flies that we sometimes see in more of a household setting? And just for an example, when you see dogs that have major fly bites on their ears or on their tails, is that the variety of fly we're talking about in that situation?

Sonja Swiger (06:08):

It is. That is the stable fly. And that's the thing about it and why it can be so problematic is that, yeah, we usually talk about it in the livestock sense and the cattle sense, but again, they're normally with horses and they have a huge impact on dogs. And I get a lot more calls in the western areas of even Texas, and I would assume even in Oklahoma that would be the same. And I don't know if it's because what the situation is, but they seem to be just more frequently attacking the dogs and they bite the ears, they'll probably bite the legs. I have a Great Dane and it bites the side of him because I guess it thinks, 'Well, it's just a small horse anyway'. So yeah, they're very painful biters and we generally see them in our cooler months. They're not really found in the summertime. They don't like it when it gets super hot, but we can have them throughout the entire spring months and then they can even come back in the fall. I've even seen them in the middle of Christmas break. They can be really bad if you having a mild winter. So yeah, very problematic species.

Lynsey McAnally (07:07):

And I am assuming those are probably the ones that when you get bit and you feel like you might have gotten shot by a very small gun?

Sonja Swiger (07:16):

I would say so too, because I know I've been bitten and you won't forget it. Not as bad as the horse and deer flies, but you're not going to forget the stable fly bite either.

Lynsey McAnally (07:25):

They're very painful. And one of the things you mentioned was that they only bite one time a day, which if you have a bunch of them it doesn't seem that way. But each fly is only biting one time a day. Can you talk a little bit about why that is a problem?

Sonja Swiger (07:41):

Yeah, I mean in comparison to the horn fly, which again is a much smaller species, it stays pretty much always on the cows. It's taking sips and it's not designed to consume a lot. But the stable fly is more like we think of a mosquito. When it goes in for a bite, it's going to fill up completely. So they're going to get on there, they're going to grab hold as well as they can try and get in a spot. They're not going to get knocked off and then just go in for that full blood meal at once, which could take a few minutes. Then they're off to digest that blood meal, which can take 24 hours or so. So yeah, they only take a single bite a day.

Lynsey McAnally (08:14):

And when it comes to, and we'll talk a little bit more about control methods, they may not be in place quite long enough for that to be effective.

Sonja Swiger (08:24):

Correct. Or because of the fact that most topicals are generally directed to where we see the horn flies, which was the back of the head and up on the shoulders and on the back, that's not necessarily going to provide contact to where the stable fly likes to bite at. So they may not even interact with some of those products.

Lynsey McAnally (08:41):

Another thing that you mentioned about stable flies is when we see cattle that are obviously uncomfortable, so stomping, bunching, maybe getting into ponds or some sort of water source, that would usually be a stable fly issue.

Sonja Swiger (08:57):

And that's very indicative of their presence is the animals will stomp and be kind of kicking their legs around. You can see the twitching of the skin. That's them also trying to deter them or the flicking of the tails trying to reach 'em. But another thing I've noticed is definitely them getting into water at a time that you wouldn't think they really need to swim. Obviously right now it's been in the hundreds for several days or close to it, and cows are in the water all the time trying to keep cool, but this is a species that's out there in the springtime when it's gorgeous weather and it's really not a reason to be in the water. But if you're seeing them in there, it's because they're trying to prevent accessibility for these flies to come and bite them on the legs. And another thing they do is they bunch, so they'll get into kind of a tight group in the pasture - or even on a dairy if we have anybody listening who's associated with them - we'll see them also in the dairies. They do this too. They'll get real close together and what they're doing is the cow inside or the cows inside the group will not get bit as often because the fly will attack the outer cows. So it's kind of a protection thing, but in the end, it's actually not good for the cows because it causes their body temperature to elevate by being in close quarters like that with everybody.

Lynsey McAnally (10:11):

Obviously, the flies are going to take the path of least resistance. So they're going to go to the animals on the outside of that group. They're not going to pass over a perfectly good meal to go to the animals in the center of the group. But like you mentioned, that can cause issues, especially if you're in an area we were a few weeks back where we had pretty high humidity. Even a small rise in humidity and those high temperatures with cattle bunching, whether that be in tall grass or weeds, they're not getting that airflow. And it definitely started to take a toll on some of our herds locally from a comfort standpoint just with the bunching and the heat that we saw.

Sonja Swiger (10:56):

Yes. And that's definitely something we don't want to add to them when they've already got plenty of other things to worry about. We don't need to stress them out more.

Lynsey McAnally (11:03):

Sure. And there's one more type of fly, I believe it's the house fly, that you spoke about as well. Do you mind telling us a little bit about that critter?

Sonja Swiger (11:12):

Yeah, I mean everybody's pretty familiar with the house fly. They are, as they say, very cosmopolitan in that they like to hang out with all types of people and all types of animals. I do think it's situational sometimes when it comes to their presence in a pastured situation. Gnerally you go out in the pasture, you're not going to really see a ton of house flies out there with the cows unless you are providing some type of supplemental feed that may have some good tasting ingredients that the house flies want to take part in. But where we generally will find them in higher numbers will be around the barn. So if you have animals in a barn or near a barn or you've got the feed in the barn, that's definitely going to be something that will attract the house fives. And then barns are usually close to humans, so they're usually going to have houses nearby, so that increases the chances of seeing them.

But obviously house flies are not just an animal problem, so to speak. They can be a problem in urban areas too, but they're very difficult to control. And because of this diversity, they are very capable of surviving all types of conditions. They're one of those insects that we know will be here until the end of the world because they just have that ability to adapt and feed and grow in so many different locations. And because you're dealing with something that is so capable of surviving and they grow so fast and they lay so many eggs, control methods have to be continual and constant and what you would say out of the box thinking. It's important to realize that one thing you do is not going to be enough. You're going to have to continuously do either that same thing or multiple things to get the proper control. And I think sometimes people expect one attack - 'I did this today, now my houseflies should be gone' - will be enough, and they get upset. But that's just not how the housefly works.

Lynsey McAnally (13:02):

I've seen several posts here recently where people have been discussing fly strike.

Sonja Swiger (13:09):

Yeah, so flystrike is usually a term that's related to when you see eggs or larvae on an animal. So they were laid there by a fly. Generally they're blowfly species, which we hadn't even talked about those yet. That's going to be a difference. Not saying a house fly won't, just kind of on the rarer side. Blowflies are more of a beneficial in my eyes because a decomposers kind of species, they actually lay their eggs that will then hatch into larvae that will eat up material that most of us find to not be very favorable, which it would be like manure or rotting substrates of that many types. But a lot of times we're talking Parkes, so dead animals. That process is good for us because it helps keep everything cleaned up and everything breaks down faster with their presence. But when you're dealing with fly strike, that's a little different because these flies have chosen to put their eggs or their larvae onto an animal that is still alive, and that can be obviously a big concern. Generally it leads to just a small wound or sore that needs to be managed just because you don't want to leave maggots in the animal.

Lynsey McAnally (14:17):

This is one of those conversations I feel like maybe we need to do a trigger warning for. But it's so interesting! We'll talk a little bit later on in the episode about a type of blowfly when it comes to New World screwworm, but what is the best control method for those flies outside of some of the ones that we'll talk about in a second? When it comes to the three previous fly species.

Sonja Swiger (14:43)

There's many different species of blowflies. I think some have a tendency to be more inclined to cause fly strike. That will vary based on where you are and what animals you have. The bigger concern there is you just wanted to kind of make sure you keep animals clean. Sometimes it could be because some matted feces on that animal and maybe that attracted the fly. Sometimes it could be there was a small wound or that got infected or festered or something of that sort because most of the time they are coming in to eat what we would call the necrotic or the dead tissue.

Lynsey McAnally (15:18):

What I took away from your presentation in Woodward was knowing what type of flies you have is critical to selecting the correct control method.

Sonja Swiger (15:27):

So most of the products on the market that you'll find to be used on cattle are going to be labeled for horn fly usage. That's because of the impact that the horn fly has directly on the animals and on the industry. If it's labeled for horn flies, it's an approved option for your cows, so then you can kind of put it on. It's going to help protect against other flies. But generally when I speak through the products, I speak through 'em in the way that you would purchase them to use to control against horn flies. Knowing that if you're using this on horn flies, other flies are not necessarily going to come visit either because they're going to be in contact with the same active ingredients. There are different chemical classifications with our products, and those would be the organophosphates, which are the older chemistry of insecticides than our pyrethroids, which is the newer chemistry that it's not really new anymore, but it's the newer of the two.

And then sometimes we'll also see some abamectin and just a simplification of 'em. Each one of those works to control the insect in a different way by targeting different features of their body systems so that we don't have resistance, which is our biggest concern because if we're constantly purchasing the same product or the same classification of products, eventually those horn flies especially will become resistance. Another species that gets resistant very fast is house flies, but again, we are going to talk them later because they're treated in a different method out of these products. When we're looking for something to use against our horn flies, the first thing I usually like to tell people is think about what it is you want to be doing. How do you want to treat them? Do you want to be out there on a regular basis? Do you want some separation or I only have to treat once a month if possible, and just observe in the meantime, do you have the ability to use certain products?

Do you have a working chute? Do you have a way to pen them up? Do you have a way to access your animals? And then how much do you want to spend? And those are really where you want to start: What can I do? How do I make it work? How much money am I willing to invest from there? There are a lot of things on the market. So we have our feed through products, which are just as they say something, you give to the cows to eat and the doesn't have any impact on them directly, but it goes through their digestive system and comes out into the manure, and you have the active ingredient placed right where the larva are going to grow. So that impact is to the larva stage directly, and it's all we have available to control the larva. One reason that's effective is because of a process we call integrated pest management with any of the insects we're talking about today, any of these fis, you want to be integrated, which means you want to think of many ways to try and stop them.

You can't stop something if you don't understand it, which is why we're also explaining all these things about them. But you want to try and attack the adult stage and the larva stage, and that will help bring those populations down faster because you're going after both the reproductive side and the developmental side. So that's one of those reasons. But the feed throughs are the only ones out there that will actually control that larva stage. Everything else on the market is what we would call a topical treatment, and that would be your poons, your sprays, the back rubs, the vet gun and the ear tags are the more common things. There is the bolus coming back as well, which we'll go into the feed through group. So it's another form of that, but different way of providing that tool to your animals.

Like I said, with all those, it's just really how do you want to work? Some of them have, every one of 'em has a pros and cons. Some are real effective right away. Some of 'em, they'll lose that effectiveness because again, everything does after a while of constant usage with feed throughs, if you get your animals to eat it, which they must and they get the right dosage that will hold up throughout the fly season, which is great. With the topical sprays, those are usually very short lived residual time. The poons last about a month, and then they need to be reapplied. Ear tags are known to hold up for about five months with two, but that can fluctuate if flood numbers are really high. And then the vet gun also works for several weeks before reapplication. But again, I get stories that some stuff just doesn't work for me. And then some stuff is great, and it really has to do with location and the amount of rain you're getting, what the weather is doing, how many times you've put that product on your animals and a whole bunch of other things can play a role too.

Lynsey McAnally (20:15):

Sure. And before we started recording, we had a little bit of a side conversation about what producers are applying and the importance of rotating the active ingredient in some of these products. Can you educate us a little bit more on that?

Sonja Swiger (20:34):

Yeah, I mean our main target with horn flies is to just keep those populations as low as possible. If you go the feed through route, you can mix that with pretty much any topical. The concept would be that you're using the feed through constantly on a regular basis. They eat it daily and that you should only have to do a topical treatment, either a spray or a pour on when needed kind of deal. But you could also use the feed throughs with the ear tags. You can mix and match ear tags with a pour-on. Again, you can kind of mix and match as you like. It's just how much do you want to spend because the tags and the feed throughs and the pour-ons range on the higher cost, so to speak. The vet gun is nice. You don't need to have a working shoot and you can still get your animals treated. When we're talking horn flies, there is no trap that technically will be used or can be used because they're just a lot harder. I got two boys, one's already in college that's going to be an engineer. Maybe this will be our future as we develop a trap. But we do have traps available for stable flies, which are just sticky traps that you set out on the ground. And that's because their biology is different. They will leave the host and go find a place to rest. The horn fly never goes and rest. It's constantly drinking. So there's a difference in their biology and their behavior that makes certain flies easier to trap than others. And then the house flies another one. It's easy to trap because they're kind of like the curious kid. They're always looking for something to go to. So you can always catch them off guard in their ability and their need to move around and find a new place to look for food or a new place to lay their eggs. So traps can be beneficial for some species, but just unfortunately not the horn fly.

Lynsey McAnally (22:24):

And I love that you phrased it that way with the house fly. That's probably the flies that get in your car that directly fly into your face. It seem like they want to fly into your ears or fly into your nose when you're trying to drive down the highway and you're trying to ...

Sonja Swiger (22:37):

Flies to the window until you open it and then it flies back in. So yes.

Lynsey McAnally (22:40):

Yep. So I appreciate that you mentioned that. And when I ask about mixing those different methods of control, it's because you might have a fly problem, but it could be multiple types of flies. When we talk feed throughs, that's obviously a little bit different. Some of the folks in my area in particular are feeding a protein block that has garlic in it. Is there research out there on the efficiency of garlic at potentially controlling flies or is it efficient at controlling flies?

Sonja Swiger (23:14):

It gets a lot of anecdotal confirmation. I don't want to say it can't have some use. I actually did a research project with it many years back, and we tried to figure out what was really doing. And in the field we could see a difference between treated and untreated animals from the biting stage, the adult stage. But in the laboratory, there was no impact to the larva stage.

And I've seen work done by others, other colleagues of mine, that did not show any significant difference between the treated and untreated. So maybe? But so far it doesn't seem to be consistent enough to warrant a being listed as, oh, you must story, oh, this is great. But again, if somebody is providing a feed with the garlic in it and they feel that the numbers are lower, I never tell people, okay, no, that's a terrible idea. I think that's great. If you think your animals are happier, then that's fine. That's all we're trying to do is make our animals happy.

Lynsey McAnally (24:22):

Sure. And one of the methods that you also mentioned, I see advertisements all the time for purchasing parasitic wasp or all different potential biological control methods. Can we discuss those options whether they work or in what situations they would work? And then also can we talk about the potential effect of feed throughs on beneficial insects?

Sonja Swiger (24:53):

And there is unfortunately some truth to that. Some of those actives - because of the way they work - they do disrupt the development or can have a slight impact to the dung beetles. I get asked a lot of times during discussions about how the numbers are lower in dung beetles. Generally when I go look, I can find them. Sometimes it depends on the time of day you're out there. The heat does impact them, and there are changes.And sometimes there's also changes in land usage, which a lot of people don't think about when it comes to insect impact. Sometimes it's the land use change that impacted it more than maybe technically a chemical usage. Not saying chemicals don't have an impact on the tongue beetles, but most of the time they do have the ability to find the resources to survive in. It's not going to have chemicals in it.

But yeah, if you don't need to use something that's going to come out in the manure, don't be putting excessive products out there that will harm them. But we do still see quite a few dung beetles. And actually, funny story, I I've recently finished a study a year ago on Dun Beetles in Texas, and one of our sites is Sonora, which is West Texas, very dry, very little grass. And that's where we collected the most dung beetles was out there compared to our central center, Texas, which was East Texas, which you expect those to have the higher numbers. And after it would rain a week later, we actually caught 300 beetles in one week because of the rain. So there are a lot of other factors is where I'm going with that impact those numbers. And it may not be directly because of chemical usage, but again, doesn't mean we want to overdo it. We definitely don't want to do more than we have to.

Lynsey McAnally (26:37):

No, and I appreciate you saying that. I may not have the warm fuzzies for flies, but for some reason those little dung beetles to me, I just want to protect the little guys. You don't see them very often and man, they're just trying to get their job done.

Sonja Swiger (26:53):

And there's different types of dung beetles. That's another thing. If I get in conversations with folks is we have those that are rollers and those that are dwellers and those that are tunnelers. And what that means, it's how they use the patents each time. And a lot of people are expecting to see rollers like we see on tv, but a lot of times those videos are taken in Africa where they have a lot more roller species than we do here. We do have roller species in the US but they're not as many, so we don't always get to see that behavior of them rolling the big gun ball on the ground and they're taking it back home. A lot of our dung beetles are inside the pat, so that's why I say if you really go look, you'll usually find 'em because they'll actually come up underground and tunnel up into it and then take the manure straight down or they're literally living in the pet.

And then you mentioned parasitoid wasps, which are a tool we can use a little bit more effectively than, say, beetles because they are available commercially, they can be beneficial in times. And with any of these insects, their life cycle revolves around either the impact onto another insect in the sense of the parasitoid loss or in the same ecosystem as the dung beetles. They do play a role in some sort of management and decrease in numbers, but they're not there solely to rid us of the pest species. And I always think that that's important to look out because a lot of people want to say, 'Oh, we must always use biologicals!' And yeah, I get it when they are a useful tool, but they're not always the only tool or the best tool. They're just a tool. It's like we talk about our toolbox. They're just one of the many tools you need.

So parasitoid wasps are just a little itty bitty wasp. They're called fly predators a lot of times. They actually survive by laying their eggs into the larva stage of many fly species, most of which are ones we're talking about. They are going to be a pest species. There are other per sowas that utilize caterpillars or other insects. And it's a cool concept, but again, it's not a one-to-one ratio. You're never going to have enough parasitoid wass to come out and kill off all of your flies. It's just not possible because most star flies and most pest species reproduce faster. They grow very quickly. They lay thousands of eggs and they have this mass reproduction system. So parato wass can be useful. You can purchase them and increase your populations in an area, but they're best utilized around barns or in a barn setting. And the main reason is is that when you have a barn, if you're trying to control your flies, you're going to control your manure. That's the key part. You're taking the manure out of the stalls, you're putting it someplace in a pile or composting it. And in that process, that's where you would also want to utilize those flies because you have better management of your manure.

 Lynsey McAnally (29:43):

That's really interesting to hear. It's not something I've ever tried personally, but I've seen the advertisements for those ply predators and always wondered, there's so many different options out there that you can purchase potential beneficial insects for. Even home gardens, I think it's the same concept, but you wonder, it seems like every time I've tried to purchase beneficial insects, they get preyed upon by some other sort of natural predator. So it just feels like you're

Sonja Swiger (30:14):

Feeding. I'm glad you brought that up because I always wonder around that too, even for the garden, and I love the concept, right, because we know that certain insects will control other insects or feed on other insects or parasitize other insects. So we're using what we know, but there's always that little tidbit, just like you said, you buy 'em, you go through all the trouble, and then they eat and buy something else. Or my brother one time wanted to buy praying mantis, and it was like 35 bucks for a praying mantis. I was like, that's great, but it's got wings. You know what that means? It's going to leave.

Lynsey McAnally (30:43):

I know I've mentioned this before in this conversation, but one of your primary areas of expertise involves blowflies. We've talked about Blowflies a smidge earlier in the podcast, but because of your experience with Blowflies, you've been called on to help educate producers on a new area of concern, or rather not a new area of concern, but a reemergence, the new world screw worm. So do you mind telling our audience or anyone who isn't familiar with New World Screwworm, why this fly should be a major concern for producers? Should it cross into the United States?

Sonja Swiger (31:21):

So the New World screwworm. It is a formerly native species to the Americas, including North America, that we successfully eradicated from the United States many years ago. And one reason why I always like to point out eradicating insects is not something we take lightly. We don't do it very frequently. It's only been achieved a few times. This fly was one and a cattle fever. Ticks were the other, both of which are unfortunately making their way back up to the United States. So the reason we don't eradicate things very frequently, they always come back. But the main thing and the main concern with this five species is despite that it is a blow fly. It is one of two species in the world that will actually prefer to find living animals to put its eggs onto.

So when an animal has a wound on its body, those can be susceptible to this fly coming to that wound and laying eggs on or near that wound, and then the larva will hatch and live inside that wound as it sounds. It's not a good thing. So now you've got these maggots living inside the wound of this animal. And while we do talk more about it with the livestock industry, this fly is not particularly only looking for livestock animals. It will literally lay its eggs on any warm blooded animal it can get in contact with and it can smell whatever cues it gives, these wounds will give off that will go to them and lay their eggs there. But we just see a larger impact to the livestock and the wildlife populations from this fly.

Lynsey McAnally (33:04):

One of the things that really stood out to me at Beef Cattle Short Course in College Station were the gentleman who had lived through the previous New World screwworm epidemic. They talked about how they didn't see near as many deer. It sounded like we are maybe making the connection that lack of population of wildlife may have had something to do with New World screwworm.

Sonja Swiger (33:30):

This fly is not a new species. It's called the New World screwworm because it's found in the Americas, which the Americas are the new world compared to the old world, which was back in Africa and Europe, but it was here for many years. Our oldest record to it, it goes back to actually the conquistador time period when they came over here. So it's the earliest colonists, and they had noted it at that time in the history books. And we started really doing research on it in the late 18 hundreds and early 19 hundreds and really started to see the impact. And I bring that up because it was a species that was here long before we brought cattle here, and it had to live on something at the time. And while there's no official data that I've seen that says, oh, we had low numbers because of screw worms, it's kind of just there and kind of noted because as soon as we got rid of the screwworm, we saw a huge growth in our wildlife populations.

And all it's done since then is just keep growing. So there's definitely some correlation between the presence of this fly. And one of the main reasons that is, is because it targets, again, a wound on an animal and wildlife, especially deer, the males obviously go through these periods of ruing as it's referred to in any other animals of that type that do the same behavior would be susceptible to these flies. So as they're banging their heads against each other, they're leaving little cuts on their heads and then the fly is going to come and make use of that and put its eggs there. And then as larva going to feed on that area, which when it's on the head, is very problematic because again, that can go, it could be close to the eye, it could be around the nose, it could be up by the antlers, but when they keep feeding, they're going to eat that live flesh and they're going to keep eating that animal.

And while the first, while the one larvae, as I want to say, will only be there for about a week, right? They grow within a week. They feed from five to seven days. It's not just that first set larva you're going to have on a host on an animal. There will be other flies coming in to use that site as well. So you get flies coming in at different time periods. So you can start having a problem on say a day, but that may not end seven days later, it may keep going and going and going because other flies have come in to lay their eggs now on that animal. And what will eventually happen is it will get down to a point where that feeding can technically just kind of cause a shock to the system,

Lynsey McAnally (36:08):

But it's going to get into an area where it either impacts something like a vital organ or causes some sort of catastrophic infection ...

Sonja Swiger (36:18):

Infection that will lead to the system to react to it or a vital organ or the brain. So you're in spots where the body's going to start to realize, 'Hey, wait a second, if something's off or again, secondary infection's going to set in. And that is what could potentially most likely be the killer of that animal because they've seen pictures of animals that unfortunately passed in 2016 when we had an outbreak in Florida Keys. And those animals were still fairly intact, but they were no longer alive. And they did have holes in their heads. And again, it's more of the reaction to the fact that there's a larva, a bunch of larva feeding on this animal's head.

Lynsey McAnally (36:57):

It stands to reason that new world Screwworm, if you were to have a colonization on the front part of their body, that would certainly cause some issues. And when you talk about the conquistadors, what a nasty surprise new world screwworm must have been for those individuals if they didn't have any experience with it. But when we talk about where it's currently located, where is this fly right now and how far north have they been found currently?

Sonja Swiger (37:28):

Its presence again was here a long time in the US and in the thirties and 1930s, it was determined by USDA that something needed to be done to get rid of this fly. So efforts were put forth to develop a system that rid the United States of this fly species. And that undertaking actually was the eradication program with the sterile insect technique, which is what's still used today. The usage of these sterile flies is what helps completely remove the population. It's just completely crashes population, obviously, other tools are used just like we talked about, you can't do management, which is one tool. You got to use many tools. So we do also do other things to help control that. And we eventually pushed it out of Mexico all throughout Central America down into the Panama at the Darien gap, the fly had stayed east or southeast of the Darien gap, which Darien gap is the far eastern side of Panama going into South America.

And it had stayed down there since 2006 without much movement, I'd say without much movement because Panama did see little from here and there. But Panama was basically where the fly resided. Since 2023 though, there have been issues and that has caused that fly to basically move all the way back through all of the Central American countries and now is found in the southern state of Mexico. So that includes the Yucatan and Veracruz, which are the two southernmost sections of Mexico. The closest location that's been identified as of today in Mexico is about 350 to 370 miles from the southern border of Texas, which seems far, but as we talked earlier is really not that far. I actually drove over 400 miles last week just to go give a talk and was still in the state of Texas. It's not as far away as it seems

Lynsey McAnally (39:27):

When you think of it in that context, 350 miles, that's a day trip.

Sonja Swiger (39:32):

Exactly.

Lynsey McAnally (39:32):

And that to me is incredibly concerning because we've talked about previously ... these flies, any sort of fly wildlife in general, they don't respect the lines that we as humans put up to say, this is our border, or this is a state line. That's not something that's in their realm of understanding. And so we really have to rethink our thought process on that as well. And when it comes to wildlife movement and the movement of cattle, that has become a major concern for the movement of New world screwworm too. Is that correct?

Sonja Swiger (40:11):

Yes, and that's actually the biggest concern right now is the movement of animals. So as a fly itself, screwworms generally only fly about 12 miles in search of a host. And again, like you talked earlier, if it finds one sooner, it's not going to go further than that. We don't pass up hosts just because that's misusage of energy for a fly.

Lynsey McAnally (40:32):

But I do want to say this real quick. For such a small creature, 12 miles is a very large amount of space.

Sonja Swiger (40:43):

Yeah, yeah. It's a pretty good distance. I don't know if they're going to do it at one time or if they just found that one did that over his lifetime, right? Over a couple of days. But still. And winds help too. But what we're really seeing with the movement and what was tracked early on when it started moving into Mexico is that these distances were hundreds, hundreds and fifties of miles away, right? So you got a pretty good gaps between the next infestations can only be attributed to movement of animals. And most of the time these are animals that were not moving on their own either. So these were mostly livestock, so wild cattle in particular. So obviously they were animals being moved by humans. And that's our biggest concern, and it really always has been since we eradicated this fly. That's why these systems were set up for inspection.

So APHIS job has always been to inspect when people bring different things to our country, one of which of course is animals and another is foods and different other things. And the reason they do those inspections is to keep out invasive species. And this was one on that list of preventing the return back to the United States. So it's not that we're not necessarily prepared on that half of it, but what's changed now is that now we have a larger area that's impacted with it, and it is moving in places that it hasn't been in many, many years actually in decades. And you've got a lot of people who aren't understanding entirely what this fly can do because they've never experienced it, which is what we'll do here in the United States. While you've talked about the guys and the gentlemen mostly, but even ladies too, but the folks who were around in the seventies to deal with it when it did kind of hang around in Texas and come back a few times and maybe even some spots in Oklahoma, most people were not.

I mean, myself included, we weren't even born at that time or we lived in a different state. So it was just Texas in New Mexico and Oklahoma that dealt with it at the later years. Every other state was no longer dealing with it. So we just don't have a lot of educational retention on it or even preparations and everything we did back then. We don't really do that anymore. We've changed our practices because we could, and we took for granted the fact we don't have this fly and we calve all year round and we do all these processes with our animals all year round because there's nothing to worry about. The other fly species we already talked about. Yeah, they're a nuisance, but they're not going to kill the animal if it's born in the springtime having calves in the summer and spring. Well, it is literally the death of them because this fly will come in and lay its eggs on the umbilical cord in the umbilical area, and we'll almost a hundred percent kill that animal if it's not tended to.

Lynsey McAnally (43:36):

When you have something at the very beginning of its life that's just being preyed upon like this and in a way that is particularly gruesome, how do you combat that? And I think that there's a definite mental toll that seems to have taken on anyone that you talk to who has lived through it previously. I think that any of us that did not live through the previous outbreak of New World screwworm would have a very difficult time understanding. But I hope people are going and looking at some of these images that are coming from some of our southern counterparts to see what will happen if it does get into the United States and hopefully start preparing even if it means updating some facilities so that you have the ability to catch these animals if you're not going to do stationary facilities, making sure that you have access to some form of mobile facility so that we can catch these to treat them. Because the one thing that I took away from that presentation is that if you don't have the ability to treat them, you're going to be helpless because there's no hands-off approach to controlling new world screw worm if it does cross into the United States.

Sonja Swiger (44:50):

Yeah, I mean this is a fly that when it attacks, the animals will die within a week or two if no treatment is done. So every animal with a wound has to be treated either prior or after. I mean, your hope is to find it before the fly does and get that wound cared for. But if you don't, and then you're having to do post-treatment and get all those larvae removed. And the thing is early on, of course, in any time you need to have protocols set up in which you can get your animals up, be prepared to treat them, do the wound care and kill all the larvae because any living larva is another generation, so it doesn't go away if they continue to live.

 Lynsey McAnally (45:28):

It's not just spraying these wounds, it's getting in there and physically removing each larvae in that wound.

Sonja Swiger (45:36):

These are old practices. We're not really set up. We don't really have a lot of tools at this exact moment. We have a few insecticidal sprays still on the market, but again, they have been used in over 50 years for this process. So there's a reason we don't have 'em. But that doesn't mean that there aren't folks on that side looking and trying to get this prepared. We're just hoping we can get some stoppage before it gets here. We really won't want it to come back at all because like you already said, it's a real impact to animal welfare and everyone has had the luxury of having the ability to farm for the last 50 years without having to think about this and what impact it has in those that did deal with it, have some very interesting stories. And yes, it is something you can with control, your animals will live as long as you're doing that, but it doesn't mean you want to have to do it that way. It's so much nicer to not have to worry about it than have to deal with it. For sure.

Lynsey McAnally (46:33):

One thing that I am curious about, and I think our listeners would be curious about as well ... Can you tell us at all - whether it's from experience or from talking to your colleagues - what are they looking for at the border?

Sonja Swiger (46:47):

I mean, that's tough. I would say Texas is probably a little bit better set up to manage animals. And even we have some issues with it because we've been doing it for a long time for the cattle fever tick eradication program. So that was already set forth where APHIS and Texas Animal Health Commission have folks down there right now with the ports being closed, it does cause a little issue because there's nowhere for the animals to come through to be checked. And now we have to worry about stray cattle or abandoned cattle. I think actually just read articles yesterday or this morning about that situation in particular because people are bringing their animals still up through Mexico from probably other countries and they're not being allowed in. And that causes a concern. And the biggest issue, if we can get access to the animals, we do look for that.

One of the things that they do with the Tick eradication program is they actually process those cows and they tick scratch 'em as they call it, but they're literally putting hands on the animals and looking for ticks to make sure we don't bring in those ticks that are no longer allowed in the US as we would call 'em, the eradicated species. And they also, at the same time, we're looking for any with fly larva, which we had not encountered that in many years. So of course that's something that's somewhat new for them. But right now, I know I read an article says that they're out there looking for some of these stray animals because that is a concern too, is if they do get up here and they do have the fly on 'em and they're left on their own and not treated well, the flies are going to start or going to finish off their development, and that's a concern. And what impact would that have to the wildlife, right, because you now have flies in the area. So it's all still a little concerning, obviously, because of the fact that we don't have full control,

Lynsey McAnally (48:36):

We all need to take into account that if it were to cross into the United States, we need to be prepared. So have we forgotten anything when it comes to either the three fly species we've talked about at the beginning of this conversation or New World screwworm that you'd like to mention?

Sonja Swiger (48:52):

What I do want to point out though is that we've talked a lot about how it has an impact on livestock, but it's a huge, huge, huge impact to wildlife when we talked on that too, but also domesticated animals or wildlife in urban areas. So over the years since it's been eradicated, anytime it's ever been brought back to the us, it's been in dogs. Dogs are another heavily impacted group of animals from this fly. And you talked about how the stable fly attacks the dogs, well, that's just an opening wound for this flight attack, the dogs too. So I do want that to be brought up because I think some people who think, well, I don't deal with livestock if they just happened on your podcast and want to listen to it today, but they should know the dogs are a problem, are an issue as well.

Or if you live next to somebody who has no livestock, but they have dogs, they need to know that they can also be a target for this. And I think that's important. And when they had the outbreak in Florida, they actually found an infested pig, which I'm sure was a pet because it was the Florida keys and then an infested raccoon. There are other animals that will also be utilized by the fly. It's just that we see the biggest impact to the livestock, mostly the cattle industry, but also horses are susceptible, goats and sheep and all of these animals. It doesn't matter what you are if you're a warm-blooded animal, and you could be humans as well.

Lynsey McAnally (50:14):

So out of curiosity, and nobody else may find this to be a question of concern, but you know what I do. You said warm blooded animals. Do we have to worry about this in reptiles of any sort? Not that I necessarily worry about, but I'm just thinking from a lifecycle continuation standpoint. Do we see predation of or infestation of reptiles?

Sonja Swiger (50:39):

Yeah, that's a great question. I have not seen anything regarding reptiles. Now I'm going to have to go look. I mean, obviously the water ones, anything that's in water, even if they got on them, they're going to go underwater. But I haven't seen any of the lists. I have a couple lists I follow from other countries, and none of them have reptilian species listed on there. But that doesn't mean it isn't, it just means they're not being identified. I'm seeing now it's a no to the reptiles.

Lynsey McAnally (51:15):

Thankfully, well, that's not bright spot. Well, Dr. Swiger, I might have the heebie-jeebies now, which is not a bad thing. I think that it's definitely something that we all need to be aware of, it being New World screwworm and flies in general. So thank you for enlightening us on fly control and this new concern that we definitely need to be aware of to the south of us. But with all the uncertainty and negativity in the world right now, I have one question that I always like to end Angus at Work on: what is one thing happening in your life - personally or professionally - that you are thankful for?

Sonja Swiger (51:56):

I like that. So ... let's see, what am I thankful for? Oh, I'm thankful for my family. So mom of four kids that keep me very, very busy. I was asked recently, what is your hobby? I don't have hobby. I have four children that I take everywhere because only one can drive. The other three all need to be driven, and they all play sports, but I'm thankful for them because that's really, at the end of the day, I love being an entomologist, but actually that's what I'm here for is for them.

Lynsey McAnally (52:25):

That's awesome. Well, thank you so much for joining us, and I know that our audience is going to really appreciate your insight into fly species in general, and then what we need to be aware of when it comes to New World screwworm.

Sonja Swiger (52:40):

Thank you so much. I appreciate being here.

Lynsey McAnally (52:47):

Listeners, for more information on making Angus work for you, check out the Angus Beef Bulletin and the Angus Beef Bulletin EXTRA. You can subscribe to both publications in the show notes. If you have questions or comments, let us know at abbeditorial@angus.org and we would appreciate it if you would leave us a review on Apple Podcasts and share this episode with any other profit-minded cattlemen. Thanks for listening. This has been Angus at Work!