Ep. 121: New World Screwworm – How It Spreads, What to Watch For & How to Protect Your Horse and Other Livestock

Episode Notes

**Statistics provided by Dr. Kaufman during this episode were as of the end of July 2026** 

On this episode of the Beyond the Barn podcast, host Katy Starr has a conversation with two experts who bring different, and equally important, perspectives to this growing concern. 

Dr. Phillip Kaufman, Professor and Head of the Texas A&M University Department of Entomology and Chair of the Texas A&M AgriLife New World Screwworm Task Force, explains the biology behind this destructive fly, how it spreads, what really puts animals at risk, and where hay and forage fit into the conversation. 

Then, Equine Veterinarian Dr. Neil Gray shares firsthand experience treating New World Screwworm in horses throughout Central and South America, including what these infestations can actually look like, and the signs owners may easily overlook. 

In this episode you’ll learn: 

• Why this fly is so different from the maggots you may have encountered before and what makes it so destructive
• What should happen if discover suspicious larvae in a wound, and why what you do next matters
• Does hay, standing forage, or transported forage create any risk in New World Screwworm transmission? 

Whether you own horses, cattle, sheep, goats, or other livestock (even dogs!), this episode will help you better understand New World Screwworm, separate fact from misinformation, and know what you can do to protect your animals. 

🎧 Listen now on the Beyond the Barn podcast 

Have a topic idea or feedback to share? We want to connect with you! Email podcast@standlee.com 

______________________________ 

Keep up with Dr. Kaufman and up-to-date information about New World Screwworm:

• Texas A&M AgriLife Extension New World Screwworm Website
• USDA APHIS Screwworm Website
• AAEP Infectious Disease Guidelines: New World Screwworm
• New World Screwworm: Prevention and Treatment Options 

Keep up with Dr. Gray and the Equitarian Initiative:

• Equitarian Initiative Website
• Facebook - https://www.facebook.com/EquitarianInitiative/
• Instagram - https://www.instagram.com/equitarianinitiative/  

______________________________ 

*Views and opinions expressed by guests are their own and do not necessarily reflect the view of Standlee Premium Products, LLC.* 

_______________________________

Read full episode transcript

Katy Starr (00:00:01): 

Hi, I'm Katy Starr, and you're listening to Beyond the Barn. Join me on this journey as we bust equine and livestock nutrition myths and sit down with some of the most intriguing experts from across the country. We'll also take you behind the scenes of how premium western quality forage is grown and brought to your favorite farm and ranch retail store. I'm so glad you're here. 

 

Katy Starr (00:00:27): 

Welcome back to another episode of Beyond the Barn. For decades, the New World Screwworm was something most US horse and livestock owners never had to think about. Today, it's back in the conversation. As questions spread online, so has misinformation. Can it travel in hay? What does it actually look like? What should you do if you find it? To answer those questions, we spoke with two experts who bring very different but equally important perspectives on the Beyond the Barn podcast today. Joining me first on this episode is Dr. Philip Kaufman, professor and head of Department of Entomology at Texas A&M University and chair of the Texas A&M Agrilife New World Screwworm Task Force. He has spent decades researching insects that affect horses and livestock and developing science-based pest management strategies to protect animal health. As concern over New World Screwworm continues to grow, Dr. Kauffman has been helping lead research and outreach efforts to better prepare veterinarians, livestock producers, and horse owners. 

 

Katy Starr (00:01:40): 

So, thanks for joining us on the Beyond the Barn podcast today, Dr. Kaufman. 

 

Dr. Kaufman (00:01:45): 

Yeah, thank you for having me. I appreciate the opportunity to share this information. It's quite important. 

 

Katy Starr (00:01:50): 

Yeah, it is. So, just a reminder for any of our listeners before we get started, any of the topics that we cover on the Beyond the Barn podcast are more generalized and not specific to any individual horse or any specific situation. Be sure to always work with your veterinarian regarding any medical concerns or before making decisions about your horse or other livestock animals' health. So, Dr. Kaufman, just before we get started, so we can get an idea a little bit about you and your experience and knowledge, can you tell us a little bit about your background in agriculture and where you grew up? 

 

Dr. Kaufman (00:02:27): 

Certainly. I grew up in Northern Illinois. At the time it was about 70 miles southwest of Chicago. Now it's about 30 miles from Chicago as that city has grown. It was a small town and during my youth, I was in 4-H and FFA. And it was during that time that I really began to enjoy working with livestock. And then as I grew, I worked on a number of different types of farms. And then when I entered college, I was actually an animal science undergraduate where I learned all about production agriculture and all of those sorts of things. But my graduate training shifted into entomology. And eventually I graduated with my PhD from the University of Wyoming and then had academic appointments at Cornell University, the University of Florida. And then in 2020, I moved over here to Texas A&M to take up the leadership role at the Department of Entomology. 

 

Dr. Kaufman (00:03:24): 

But we still have a research program where we study the pests that impact livestock and companion animals and even wildlife. 

 

Katy Starr (00:03:32): 

That's awesome. I love that. Okay. So, entomology, actually I'm curious, what shifted for you? What was that shift that took you to entomology? 

Dr. Kaufman (00:03:42): 

Well, it was kind of an opportunistic thing. As I was going through my undergraduate, I thought I knew what I wanted to do, but like a lot of students, you discover a lot more about the world as you go through college, which is one of the great things about college. And I had taken a summer job after I graduated, and that was with an internship up in Wisconsin. And in that internship, I did a lot of entomology and weed science and plant pathology and really liked the entomology, which I had done as a kid. And as I did my master's degree, I learned a lot more about entomology. We kind of consider ourselves a discovered science. A lot of kids don't grow up realizing that they can have a very good career as an entomologist. And as one of my former department heads in this department said, entomologists are biologists with jobs. 

 

Dr. Kaufman (00:04:38): 

And we have a lot of opportunity in entomology. I found my path and was able to bring my animal science and desire to work with livestock together with entomology to help with animal health protection. 

 

Katy Starr (00:04:50): 

That is wonderful. And it is such an important aspect of animal ownership. It's like one of those little pieces or tools in the toolbox for livestock owners that's really important, especially for the topic that we're going to discuss today. So, can you explain to us what the New World Screwworm actually is and what kind of threat it poses to the horse and livestock industry in the United States? 

 

Dr. Kaufman (00:05:15): 

Certainly. So, the New World Screwworm is not some mystical animal. It is a type of blow fly. And most people in the world have seen blow flies. There's those big metallic flies. They're often brightly colored and shiny. But this one is a little different. So, most blow flies that you will see will either be on or around garbage cans, or you'll see them on dead animals that you may see on the side of the road if you care to look at them. Blow flies play an important role in decomposing organic matter, such as when a deer gets hit on the side of the road, the blow flies are the ones that do most of the consuming of that carcass. This fly is a little different in that this fly millions of years ago, its ancestors made a switch in their biology, which is actually pretty interesting in that they decided or they became adapted to feeding on living animals rather than dead animals. 

 

Dr. Kaufman (00:06:15): 

And that adaptation switch was so powerful that right now the New World Screwworm can only survive on living animals, which is bad for us and our animals, but for them, it's how they survive. And we call those organisms obligate ectoparasites or obligate parasites. They have no other way of surviving than consuming a living animal. 

 

Katy Starr (00:06:39): 

Okay. And so how does that impact our industry here in the United States then? 

 

Dr. Kaufman (00:06:44): 

So, this fly is also so damaging because as it feeds, it gets bigger and bigger and causes a small wound to become a very large wound. And in many cases, while they're feeding, they're actually killing quite a bit of the tissue in the wound. So, if you think of you have a cut on a muscle area, the fly is in there eating the muscle and the fat and the other tissue. That wound instead of healing gets larger and larger. And as they feed, they're killing that living tissue. And the part that they don't eat has died and it starts to rot. That creates a bacterial soup that if it gets bad enough, enters the bloodstream. And that's what we call when the bacterial infection goes septic. And it's actually the bacterial sepsis that often kills animals. And it's incredibly painful as well. So, this is not something we want to ignore. 

 

Dr. Kaufman (00:07:38): 

It's something we need to address as part of an animal health issue. We need to identify these flies in the animals, treat them, get those maggots out of the wound and kill them. Because although this is a native fly to the Americas, it's one that we eradicated from the United States and eventually Mexico and most all of Central America 25 to 50 years ago, depending on where you're at. Because it was so damaging. It's estimated that this fly killed 80% of the white tailed deer fawn crop in Texas every year while it was here. And it is not something we try to manage. It's something we are trying to eradicate. We want to get rid of it so that our animals stay safe and our agricultural economy doesn't suffer from that. 

 

Katy Starr (00:08:27): 

Right. Okay. So, so far in this, what would you say is maybe the biggest misconception that you've heard or experienced about the New World Screwworm that you kind of like to just set the record straight about with our listeners today? 

 

Dr. Kaufman (00:08:43): 

So, there are a couple. One of them is that if an animal is infested with New World Screwworm, that that animal can no longer be consumed. And that is false. Certainly an animal that presents at slaughter with Screwworm larvae on it is directed differently in the process. It may not even be slaughtered. It may be removed from that process and sent for recovery. But this is not a disease. This is a parasitic infection and it's just like any other infection that if we treat it, the animal recovers, then that animal is safe to consume. There is absolutely no danger to the food supply. And people do not need to be concerned. They will never see one of these larvae in any beef products or other animal products that they may buy at the store. 

 

Katy Starr (00:09:37): 

Okay. That's good to know. 

 

Dr. Kaufman (00:09:39): 

The other is that we have groups that believe that in the past, the Screwworm would move up into the Great Plains state, Oklahoma, Nebraska and Kansas. That movement was not because the adult fly flew up into those areas and established. It's because humans moved animals with infections during the summertime up into those states. And they didn't understand that they were actually moving and transporting the animals up there. This fly is actually quite rare in nature and it is not like a swarm of locusts. There were groups that though that when the fly came across the border, it would be a mass movement of flies and you would see them all over the place. This fly is quite rare in nature. And the average person is probably never going to see an adult fly. And we have had a number of people, and we're happy to take those pictures, send us pictures where they believe they have seen a New World screwworm. 

 

Dr. Kaufman (00:10:40): 

In fact, there's a second Screwworm in the US that does not feed on live animals. And it's actually quite common. And it's the fly that they're most likely encountering called cochleamaya masilaria. Whereas the New World Screwworm is cochleamaya hominovorax, which means man-eater. 

 

Katy Starr (00:10:58): 

Yeah. 

 

Dr. Kaufman (00:10:59): 

And the last misconception is that we are not doing appropriate management to eradicate this pest, that we rely on the sterile insect technique or SIT to do the eradication. History tells us that SIT works. SIT is, and we can discuss that a little later, but SIT is a practice where we used sterile flies to find those wild flies and help us eliminate them from being able to propagate in the wild. And so we eventually crash that population. SIT works. We used it in the original eradication. We used it in Florida in 2016 to eliminate that Florida key deer population outbreak. And it will be what we use to eradicate the pest. And we are gaining additional flies every week because we just opened a plant in Southern Mexico that is adding flies to this. What we lacked was the number of flies we needed to push the population back south, but those challenges are being rectified now. 

 

Dr. Kaufman (00:12:11): 

We are producing more flies. And as time goes on, we will add more and more flies to this outbreak that we're having. 

 

Katy Starr (00:12:20): 

Yeah and I will say, you had mentioned this in some of our pre-discussions for this episode as well, that we're living in a time now where we have a lot better access to different technology and resources than we did decades ago when this was eradicated previously, right? 

 

Dr. Kaufman (00:12:39): 

Absolutely. So, your older audience may remember the little boxes that used to get tossed out of the airplanes to disperse the flies. And that is not what we do anymore. We actually have the flies in airplanes. They're chilled down as adult flies. And using GPS technology and knowing the habitat that the fly lives in on the ground, they will fly a pattern, kind of like a grid, just back and forth over an area. And they have computer aided technology that augers the flies out of the back of the airplane so they're not dropping boxes of flies. They're actually releasing the fly itself. And as it falls to the earth, it warms up and then it flies off. It knows where it should be looking for its mates. And it's a great advantage because it's making better use of those limited flies that we have available. 

 

Dr. Kaufman (00:13:34): 

We also have much better animal health products. A lot of the products that we have now were not available in the 1970s and 60s when we had this the last time. Yeah. And we understand better the animal movement implications of how and why Screwworm moved out of Texas every year. And we don't do that anymore. And it's because we understand we were, in a sense, our own worst enemy in helping this fly move around. 

 

Katy Starr (00:14:01): 

Yeah, absolutely. Okay. So, why don't you talk to us a little bit about the life cycle of the New World Screwworm and what that looks like? 

 

Dr. Kaufman (00:14:10): 

Yeah. So, a normal blow fly will lay its eggs on a dead animal. This fly will not lay its eggs on a dead animal. The female fly will only lay her eggs in an open wound. So, if you have a wound site on an animal and it can be as small as a tick bite, the female senses something in that wound that says, "This is a great place for me to lay my eggs so my offspring can survive." Right. So, she'll fly and seek out that animal, evaluate that wound to see if it's suitable for her offspring, and then she will lay eggs in the wound, along the edge of the wound. If she's left undisturbed in 15 to 20 minutes, she can lay anywhere from 200 to 400 eggs. Those eggs hatch in about 10 to 12 hours, and those larvae hatch and immediately crawl into and start burrowing into the wound. 

 

Dr. Kaufman (00:15:03): 

Most of the time they're not up at the surface. They're down in a pocket down further where they start to feed. And over about five to seven days, they grow through three larval stages that are progressively bigger. And you eventually get this very nice sized maggot that when it's finished eating and is at full size and they have kind of stretch receptors that tell them, and then hormones that dictate their behavior, their behavior changes. They stop eating. They crawl up to the surface of the wound and fall out of the animal and fall onto the ground wherever that animal may be standing. Those larvae then burrow into the soil. They become photophobic, so they don't like light anymore. And they try and find a place without light. That often means they burrow into the soil or underneath leaf litter. They then transform into a pupa and that pupil stage is kind of like when a caterpillar transitions into a chrysalis that then becomes a butterfly. 

 

Dr. Kaufman (00:16:03): 

That's what happens with blow flies is they go into that pupil stage, transition from the larval form to the adult form. They push the end of the cap of the pupil case off and then they crawl up through the soil as an adult fly. And then after five to seven more days, that female starts looking for a mate. And that's when the male flies will meet with the female. And then she develops eggs over the next five to seven days. So, about two weeks after she comes out of the soil, she is ready to lay eggs and start that process over. The whole process takes about a month, but it's, they're cold-blooded animals, so it's all temperature dependent. And this is a tropical fly. It does not like cold temperatures and it does not like really hot, dry conditions either. And that's why it dies back every winter. 

 

Dr. Kaufman (00:16:52): 

So, it dies back to the Southern Texas or Northern Mexico every winter. And that's where we're hoping to get ahead of it and maybe push it further away from the border over this winter. 

 

Katy Starr (00:17:03): 

Okay. Yeah. No, that is actually great to hear. So, I guess our biggest worst enemy in that case is if we're not paying attention and we're actually transporting the horses or livestock that may be infected. That's what's really going to push it out rather than the New World Screwworm itself actually getting further along. 

 

Dr. Kaufman (00:17:25): 

Right. And to a certain extent, we may have witnessed some of that with the current outbreak. So, back in early June, the fly, we found initial cases of myiasis or live larvae in a live animal is what myiasis means. That was found in, I think June 2nd, June 3rd in Southern Texas. And then very quickly we found cases in some of the other counties down near there, but not adjacent to it. And that's indicative of people probably moved animals without recognizing that the fly was a threat, which is why we want people to very often put eyes on their animals and check them. Right? If we can find those myiasis cases, those larval cases early enough, we can very, very effectively treat those, remove them, treat the animals to make sure that any we might have missed are killed. And then that animal has a chance to be protected and heal up so that they don't keep getting new eggs laid on them. 

 

Katy Starr (00:18:31): 

Okay. So, you mentioned early June this year, that's when we first discovered it back here in the United States. So, what protocols have been put into place to help mitigate the spread further into the United States? 

 

Dr. Kaufman (00:18:47): 

Several things. So, we have been working on these response plans for over a year and a half. Mm-Hmm. So, since November of 2024, the Screwworm groups in Texas have been getting together and developing plans in coordination with USDA APHIS. So, in the United States, the New World Screwworm is considered a foreign animal disease pest. And even though it says the word disease, it's not a disease. It's a parasitic infestation. And we work together kind of poking holes in each other's plans to make sure that we identified all the routes of movement and everything else. What happened in Texas is we have a fantastic state agency called the Texas Animal Health Commission. That agency was named by Governor Abbott to be the lead state agency for the response to the New World Screwworm in collaboration with Texas Parks and Wildlife, the state agency that governs wildlife in the state. 

 

Dr. Kaufman (00:19:46): 

And those groups worked with a number of the other groups of us, including Texas A&M AgriLife to develop these plans. And what happens in Texas is when they find flies and someone reports, and that's absolutely critical that people report, is we tell people, if you tell us you have this fly, you will get sterile flies dropped on your property within 48 hours. And USDA APHIS has been fantastic about that. They are currently dropping four million plus flies on every one of these infested zones that we have in Texas. And that's really done to suppress those wild flies that we can't get to because once they're an adult fly, they're very difficult to address, right? Because they have wings and they can move around and they hide. And they're not easy to identify. So, what protocols we have is when an infestation is found at a site; Animal Health Commission essentially drops a pin on that ranch and then goes out six miles in every direction and draws a circle. 

 

Dr. Kaufman (00:20:48): 

That area is called an infested zone. They sometimes use the word quarantine, but quarantine is just a legal term that gives them some administrative privileges for doing animal inspections and stopping movements. It really is not an, a true quarantine because in this case, that infested zone has animal movement restrictions. And initially there's a 72 hour moratorium on any animals moving out of an infestation zone. And that's done to enable Animal Health Commission to position their people in and around that area because they need to go and talk to the property owners or the ranchers, the homeowners, the pet owners in that area. They need to go talk to those individuals to share information on New World Screwworm and to identify and see if they can assist with animal inspections on those ranches. Because after the 72 hours, if you have a ranch in that area and we want to make sure that business can continue, you can ask for an animal inspection to occur. 

 

Dr. Kaufman (00:22:01): 

And an animal inspection is if I have a bunch of calves that I want to send to a feedlot, I contact them. They send a certified inspector that they have trained who will come and work with my team to examine my animals. And then depending on where I'm going to move those animals, there are treatment protocols. They may, that in different cases, there are going to be different pesticides or animal drugs that they will require you to treat the animals with. We have several that are available now. Some of those require that the animals be held for 48 or 72 hours. And that's simply because that's the amount of time those drugs take to get distributed in the body. So, that we make sure that when we put cows on a trailer and we send them 300 miles away, that we're not moving maggots 300 miles away. 

 

Katy Starr (00:22:54): 

Right. 

 

Dr. Kaufman (00:22:55): 

It has worked very well. They've been able to cover the requests that people have made. I missed the number this morning, but I believe they have inspected over 25,000 animals in Texas so far and issued over 900 movement permits. And so we are able to keep animals moving. The livestock markets in the state are still open and several of those sit inside these infestation zones. We're up to 18 infestation zones in Texas now and 42 total cases since the outbreak started. 

 

Katy Starr (00:23:28): 

Have those all been cattle? 

 

Dr. Kaufman (00:23:29): 

No. I don't know the specific numbers, but I would say about half have been cattle. And nearly all of the cattle infestations have been newborn calf with calves with umbilical wounds that have been attacked, which is a favorite site for this fly. There have been a number of goats and sheep. The goat and sheep infestations probably most frequently have been castration sites or tail docking. There have been a few where there've been some mammary gland issues and there have I believe been two or three total dogs. 

 

Katy Starr (00:24:02): 

So, no horses yet, which is good? 

 

Dr. Kaufman (00:24:05): 

Oh, that's very good. And so to my knowledge, they've not identified any issues in horses. And horses are still certainly a very important part of the Texas agricultural group of animals and they are susceptible as well. 

 

Katy Starr (00:24:20): 

And so previously you mentioned a little bit about the sterile insect technique. Was there anything else you wanted to add with that as well? 

 

Dr. Kaufman (00:24:27): 

Yes. So, just I can try and quickly explain it. So, sterile insect technique is a, an idea, a concept that was developed almost 100 years ago by one of the graduates of my department, which I'm very, very proud of. Edward Nippling, who went on to a fantastic career in the USDA. He and then some other colleagues that he worked with kind of came up with the concept. And the idea is that if we can, it's called area-wide pest management. Instead of treating an individual animal with a fly that has a wide distribution, you can, let's let the flies themselves help reduce their population. It works in this case because the female sterile fly mates only one time in her life. So, if she mates with a fertile male, she gets the sperm from the fertile male and she holds onto it. And then as she lays eggs, she releases sperm onto those eggs. 

 

Dr. Kaufman (00:25:23): 

It gets fertilized and then it produces an offspring, an embryo or a maggot later. If we can get her to mate with a sterilized male, she thinks she has mated with a male that provided her with sperm when in fact he didn't. And she goes on and lays eggs, thinks that she's fertilizing them, but in fact they're not fertilized and so those eggs will never hatch. We can do this because they develop techniques to rear the fly on an artificial diet. So, the flies are not raised on live animals. There are animal products that are used in it like dried blood and egg that are part of that mixture, the larval media. And then we can raise these flies by the hundreds of millions in factories. There's currently one production factory in Panama that produces about 100 million flies a week. So, about 17 million flies a day. 

 

Dr. Kaufman (00:26:17): 

When we mass produce those and it's all very temperature and timing controlled, you'll produce say 17 million flies that when they get to the pupil stage, they let them age to a certain time. I think it's about four or five days. And inside that pupil case, the adult fly has done all of the development it needs to become an adult. They then take those flies, put them into a canister that's kind of like the size of the giant coffee canisters you might buy at Costco or Sam's. So, it's about seven liters and they set that next to a radiation source called Cobalt 60, which emits gamma radiation. So, essentially waves that penetrate the fly pupae and break apart their chromosomes. And they do it in such a way that the chromosomes, you normally have DNA that repairs. In this case, they damage the DNA so much it can't repair itself. 

 

Dr. Kaufman (00:27:18): 

And the cells are alive, but they can't reproduce anymore. And you've killed all of the sperm and all the eggs in those flies. They then let the fly emerge. It looks and acts just like a regular fly. We fly those pupae up right now from Panama to Southern Texas and Northern Mexico. They're broken into different size groups. We put them into a container that coats them with fluorescent dye. So, powder that when you put it under a black light glows, they use green and red. And they do that so that if they catch those flies on the traps later, they just have to put a black light on them and they can tell that they're a sterile fly and they don't have to dissect them. So, they let them emerge. They get 17 million of them out in a day. They put them on the airplanes or they have ground release stations where they take the pupae and just put them in the field and they release those flies into the environment. 

 

Dr. Kaufman (00:28:14): 

Those male flies now just zip around, find the females in the wild, mate with them. And that female, although she's still alive, she will never contribute to more offspring. And so, you eventually, you kind of collapse the population because you can't, they don't have enough of them in the wild to continue you know, developing. Because if you think about it, I said the fly's quite rare in nature. If you have a male and a female that produce offspring and they, most of these insects will produce maybe two successful offspring, that gives you a stable population. If they produce three or four, your populations go up. If they produce less than two, it crashes. And so what happens is over, over several weeks, that population in an area crashes. And so you see fewer and fewer real cases of myiasis, and eventually you've eliminated the fly from the area. 

 

Dr. Kaufman (00:29:13): 

And it works because we can produce, mass produce these flies. They just opened a plant in Matapa, Mexico. And just this week they produced three to five million flies themselves that are adding to the fly, the hundred million flies from Panama. And within a few months, Mexico should get to hundred million flies themselves. And we're building a plant in Edinburgh, Texas that will add eventually three-hundred million more flies. So, we will end up with five-hundred million flies. And with that number slightly less, we'll be able to start pushing this fly back down to Panama where we had it contained for 20 years. 

 

Katy Starr (00:29:52): 

No, that's amazing. So, what can horse and livestock owners themselves do to either prevent or reduce the risk of their animals contracting this? 

 

Dr. Kaufman (00:30:04): 

So, the best thing anyone can do for their animals is to put your two eyes on your animals. Look at them, evaluate them, watch them. Because you can't prevent the fly from coming and laying eggs, but you can prevent that wound from getting worse with maggots in it if you, particularly if you know there's a wound on that animal, you need to treat it in a way that you create a physical barrier, right? The vet may put a bandage on there and that's fine. There are some other products, some materials you can spray that kind of create a cover on it. Now, a lot of animals will lick that off, but if you know you have a wound, check the animal every day. And if you find maggots, have your veterinarian come out. Veterinarians are critical to this process because some of the best chemicals that you can use on your animals, including for prevention, can only be used by a veterinarian. 

 

Dr. Kaufman (00:31:02): 

And your veterinarian has a lot of options, or I should say a number of options that you don't have. So, the best thing, two eyes, the second thing is to get a veterinarian who you have a relationship with so that when you call them, they are able to do that because they can't just walk on a farm and treat an animal. They have to have what's called a veterinary client relationship for them to do work with you, especially when they're going off label with some of these products that they're allowed to do that with. If you know you're having newborns being delivered, you need to pay extra special attention to them. So, the newborn animal is probably the animal at the greatest risk of infestations. And again, look at the maps that are on the Texas Animal Health Commission website. It shows you where they know Screwworms are active. 

 

Dr. Kaufman (00:31:52): 

If you are in one of those infestation zones, you really, really need to take this, especially seriously. If you're 200 miles from that, it's still a good idea to check your animals, but the likelihood that you would have Screwworm is quite small. And so it's all risk management and being the best steward of your animal's health that you can. You know, there are some products that you can use as preventatives. We have a lot more of those with the companion animal side than we do with the livestock, because with livestock, especially the livestock that we eat, we need to be very careful that we aren't treating them with products that we then don't want to enter the food stream. And we are very careful with that. 

 

Katy Starr (00:32:37): 

So, we have heard some questions from horse owners about some of the next few questions. So, I'm hoping you can help us understand this a little bit better. But can horses or other livestock, I mean, you've talked a little bit about how the New World Screwworm, it travels and what it does to kind of take on to an animal and everything. But can they get the New World Screwworm from hay at all? 

 

Dr. Kaufman (00:33:02): 

Absolutely not. This fly will only lay her eggs in an open wound. She could care less about hay and she won't even sit on a hay bale or hay bales. They don't go in buildings. Yeah, so there is absolutely no worry about them associating with hay. The only risk is if, if the feed is going to cause a wound, then they're opening their animals to a wound, but that's not likely with, with feeding hay or having hay in the property. 

 

Katy Starr (00:33:33): 

Right. Right. And so I know probably what your next answer will be as well, but just to kind of, you know, ease some concerns, so it wouldn't even, It's not going to lay eggs. It's not going to cause any problems with any standing forage before harvest or anything like that as well. 

 

Dr. Kaufman (00:33:50): 

No. Oh, no, no, it will not. So, what they're probably thinking of are things like blister beetles that often will show up in alfalfa type hay. When they cut the hay, they kill the beetles and then they're stuck in the hay and, and that can sometimes cause some problems. But this is a whole different insect with a whole different biology. 

 

Katy Starr (00:34:11): 

Yep. Yep. Oh, that's excellent. You're right, actually. That's probably where, especially some of the folks that are there kind of in that Oklahoma, that region over there, I know that can be of some concern with the hay there. And so that's actually probably where they're thinking about that. So, we also have horse owners, obviously, that travel. And so we have some concerns about, like, could the flies or the larvae be transmitted in hay bales or something like that? So, again, I think I know what your answer's going to be, but transported hay shouldn't be considered a risk in this case. 

 

Dr. Kaufman (00:34:49): 

Absolutely not. And it's important to understand that the fly larvae are not going to leave. If you have two horses, say that are stalled next to each other or even in the same stall. If you have maggots in one animal, even if there's a wound on the adjacent animal, those maggots are not going to crawl out and go to the other animal. They develop where mom dropped them as eggs. And that's the only place. They don't even move from a one wound on an animal to a different area on that animal. They stay in that spot. They're kind of stuck. 

 

Katy Starr (00:35:21): 

That's excellent. I think our listeners will be really glad to hear some of that information about that, because that's, that has been a concern for some of them, and so I'm glad we can discuss that a little bit more. And so from your perspective, , what are the chances then of us being able to get a handle on the New World Screwworm and eradicating it from the United States again? 

 

Dr. Kaufman (00:35:43): 

I am 100% positive we will re-eradicate this fly from the US. We've already seen, if you, if you track the numbers of cases in Texas, we've already seen those case numbers start to drop, which is what we often see with Screwworm when we do sterile insect technique releases. And this is a huge kudos to the ranchers, all of the animal owners in that part of Texas, is they are taking this dead serious. They are following the rules and regulations that we worked so hard the last year and a half to develop in the plans. And it's only going to get better as we bring more flies online. And then as, as temperatures drop, those colder areas, areas that where sustained temperatures are below 59 degrees, the fly will eventually die out in those areas if we weren't able to get rid of it before then, but I think we'll probably be rid of it before we even get to winter. 

 

Dr. Kaufman (00:36:41): 

When you have an infestation in an area and they start releasing the sterile flies, they release them for 90 days after the last Screwworm case was found. And that's intentional because they're trying to get past more than two potential generations of the fly. And all the models that we have in history tells us that if we do it for that length of time, we essentially quash those populations and we are safe. And I think, you know, when we look at that, if we're looking now at the very end of July, the case that just was announced yesterday, so they'll release flies there to the end of August, September, end of October. And by that time, we're going to be getting into the cooler areas. That particular part of the state doesn't get especially cold usually, but it probably will get cold enough that even if we miss some, they'll likely die out. 

 

Katy Starr (00:37:30): 

And so from your expert perspective and experience, we've had a really good discussion today on the New World Screwworm, but what key takeaways would you like to leave our listeners with about the New World Screwworm? 

 

Dr. Kaufman (00:37:46): 

We defeated this pest not just once, but multiple times. We eliminated it the first time from all of the US in a matter of years. The last cases we had in the US were in 1982 in South Texas. And after we pushed it further south in Mexico, we were done with it. And that was 44 years ago. When it showed up in the Florida Keys, APHIS dropped in very quickly. They eradicated the pest again. We've eradicated it from Curacao multiple times. We've eradicated it from Libya. Sterile insect technique works. What we lacked when this started was sufficient numbers of flies to be able to have stopped it further south, but those flies are now becoming available. We have a genetically modified fly that is likely to be added to the mix, which will, in all intents and purposes, double our fly production. So, instead of the targeted 500 million flies that we plan to have, we may have on the order of an equivalent one billion flies to release every week. 

 

Dr. Kaufman (00:38:51): 

And that gives us a lot of other opportunities to maybe make this eradication happen faster, right? Right now, all of Central America is, is suffering from this because they're not getting any of these sterile flies. But we have a very well-trained set of personnel and, you know, all kinds of websites with updated information. People can find information as they want. And I'm very positive that we are going to see that we are ahead of this. And I think next summer, even if it were to make an appearance in Texas, we will have a lot more flies available and we can, can get on top of this even faster than we were this year. And perspective, we had similar conditions in 1972 in Texas. We had a very low year in 71. Great winter for the flies, bad for us over 71, 72. 1972, we had 91,000 cases in Texas. 

 

Katy Starr (00:39:49): 

Oh, wow. 

 

Dr. Kaufman (00:39:50): 

Over the whole summer that were reported. We have had 42 to date. We are doing so much better than we have in the past. That's because we learned from the past and the ranchers and the horse owners and the pet owners are listening and following instructions. And as long as we all stay together and keep doing this, we'll be okay. 

 

Katy Starr (00:40:11): 

Work together. Excellent. So, Dr. Kaufman, how can our listeners stay connected with you after this episode to kind of keep up with all that's going on with this topic? 

 

Dr. Kaufman (00:40:21): 

Certainly. So, you know, we have a Texas A&M Extension New World Screwworm website. And anyone can go into Google Search and just type AgriLife Extension Screwworm or Extension Screwworm, and it should pull up our website. We keep adding new information. We just did, recorded a Spanish language webinar yesterday that in probably a week or so we have, hope to have posted. The screwworm.gov website is where the most up-to-date information on cases and other things are posted, and folks should be checking that regularly. You know, we keep adding information, but we're also doing speaking engagements all across Texas and in other states. And so check with your local county extension office if you're interested in coming to one of those, because they're all open to the public. And just come on down and listen to it. You'll get a chance to talk with the experts. 

 

Dr. Kaufman (00:41:18): 

I am one of many. There are a lot of us around the state and we're all working together. But if you want to meet any of them, go to one of these county extension programs. The commodity groups are often putting these on as well. And, you know, we love hearing from our constituents and ideas. But again, if you ask your county agent and they don't have the answer, they know how to get the answer. So, don't ever think you can't get an answer to something. 

 

Katy Starr (00:41:44): 

Excellent. Well, we'll be sure to include the links that you shared in our show notes so it's easy for our listeners to find. But other than that, Dr. Kaufman, thank you so much for being on today and giving us such great insight into the New World Screwworm, helping us have a better understanding of how it works, because I do think there's some misinformation out there and misunderstandings. And so I think this was a really helpful conversation today. 

 

Dr. Kaufman (00:42:09): 

Absolutely. Thank you for bringing the topic to everyone. 

 

Katy Starr (00:42:13): 

Understanding the biology is one thing, but what does it actually look like when cattle or horses are affected? That's exactly what I asked equine veterinarian, Dr. Neil Gray, who has treated New World Screwworm firsthand. Joining me on this part of the episode is Dr. Neil Gray, a retired equine veterinarian who spent more than 35 years in private mobile practice before dedicating his time to international veterinary outreach through the Equitarian Initiative for over 10 years. Since 2013, he's worked on projects with working equids throughout Central and South America. On these projects, as part of his caseload, he's seen and treated New World Screwworm firsthand. Today, he's here to share what that experience has taught him, and most importantly, what every horse and livestock owner should know. So, thanks for joining us today, Dr. Gray. 

 

Dr. Gray (00:43:09): 

Good morning. How are you doing today? 

 

Katy Starr (00:43:11): 

Awesome. We're so glad to have you on today to talk about this topic. I know it's kind of becoming a bigger deal. We've been watching it and keeping an eye on it for a while, but we have horse owners and livestock owners that are asking questions and wondering how they can make sure that they protect their herds. And so we're really glad to have you on today to talk about this topic. 

 

Dr. Gray (00:43:32): 

Glad to be here. 

 

Katy Starr (00:43:33): 

So, why don't you just get us started? Tell us a little bit about your background with horses and livestock and where you grew up. 

 

Dr. Gray (00:43:40): 

Yeah. So, grew up in Ohio in suburbia, outside of Cleveland, and started riding at a summer camp as a child. And that's what got me involved with horses. So, I was a pretty typical horse-interested kid. Cleaning stalls at local stables to be able to have horses to ride. My family wasn't into horses and it didn't really have that route open for me. So, found jobs and worked actually at a hunt club in Chagrin Falls in Ohio for the latter part of high school, which is what kept me going with horses. And, and went to vet school in Ohio as well at Ohio State. 

 

Katy Starr (00:44:20): 

So, you kind of just fell in love with horses and that was your draw to become a veterinarian. Did you figure I want to be a large animal veterinarian and work with equines? Was that your initial thought when you got started on that path? 

 

Dr. Gray (00:44:32): 

Yeah. By the time I was really probably about 15 or 16, that was what I wanted to do. I knew I, I always liked medicine. I always found medical ideas and discussions very interesting. And then once I realized that I could put that together with my interest in horses, that seemed to coalesce nicely. 

 

Katy Starr (00:44:50): 

Yeah, that sounds perfect. So, you're here to talk with us today about the New World Screwworm, especially because this is something that you've had firsthand experience with. One of the first things I was hoping you could talk to us a little bit about, we have talked with our previous expert entomologist, Dr. Kaufman, on some things, but I was hoping you could share with us about some of the signs that horse and livestock owners can look for to know if they're dealing with the New World Screwworm. 

 

Dr. Gray (00:45:22): 

So, I did get involved with New World Screwworm based on my travel with Equitarian Initiative, which is a nonprofit organization that travels into developing regions or areas with very limited access to care. Primarily working with working horses, which are communities that depend on these animals for their either livelihood or harvest work, getting goods to market, getting water to their houses. It can be very basic transportation needs or communities where it might take somebody two or three hours to get to someplace where they can get water. And so, their animals help bring jugs of water back to their house, that sort of thing. So, been involved in projects through that in Central and South America, like you said. So, from the history of New World Screwworm, as it was eradicated from the US, the '50s and '60s, I'm sure you talked about all of this with Dr. Kaufman, basically as it was being pushed south and eradicating through the countries in Central America down to the Darién Gap at the southern end of Panama, where the border with Columbia is. And with the release of sterile male flies to try to limit the numbers of adult Screwworms that were able to hatch, and you probably got into all that with Dr. Kaufman, so I don't want to repeat all that. But that program was very successful by the late '80s. It had been pretty well sequestered below that Darién Gap. But as the fly started to escape that borderline, and that was probably due to some animal movement, probably cattle smuggling, probably some animals being transported across those borders, that and the changing patterns of weather in those areas allowed those flies pushing through that border. So, what we were starting to see, I had not been working in Panama at that time, although those were the first cases north of that area came up through Panama. 

 

Dr. Gray (00:47:22): 

And then Costa Rica, which shares a southern border with Panama, started to see cases in early 2024. At that point, because it had been eliminated for a couple of generations, essentially, the horsemen in the area where we were working in the South of Costa Rica had not seen cases very often. So, they didn't really know what was going on. And what we were starting to see there were a handful of cases where the horses were starting to be infested with the Screwworm issue. And those are going to be wounds that may be obvious wounds or maybe less obvious. And the first case that we saw was in a male horse that had an infestation in the urethral fossa where you would normally get a bean in a male horse. And that was actually infested with screwworms. And that was a very, very ill animal. And again, because of the types of horses that we see and the problems that we see in some of these communities, that horse may have had some other illnesses that were debilitating as well. 

 

Dr. Gray (00:48:25): 

But he was a very, very sick animal when the owner brought him to our clinic. And we were able to clean that out, treat him with some anti-parasitic medications and larvicidal sprays and try to get rid of the infestation. I don't think that animal survived that particular episode because he was so severely ill by the time that we saw him. That's not been the most typical. Okay. More typical is an infested wound that we see. So, we had a foal a couple years ago in Honduras with a gash on its rump that was about two weeks old laceration when we saw it initially, and that was just full of Screwworm larvae. So, as I'm sure that the entomologist discussed, what happens is the, the female fly is attracted to the smell of blood. Or the smell of rotting, flesh, any sort of off odors that a wound would produce and lays her eggs next to those wounds. 

 

Dr. Gray (00:49:24): 

So, if there's a small abrasion, if there's a break in the skin for some reason, it probably not able to bury itself into an intact skin. But a very small wound, including what they say is even something as small as a tick bite could potentially create an opening for the Screwworm larva to bore into. And that's what happens is that this patch of eggs, as they hatch, literally bore into the flesh. And unlike other types of maggots, like the types of maggots that are used, in fact, sometimes medically to clean wounds because they only eat dead tissue. The problem with the Screwworm larvae is it's built to be able to burrow itself in. It's got good clenching teeth, and it's got a screw-shaped body with lines around it like you would find on a screw to be able to twist its way into tissue. 

 

Dr. Gray (00:50:16): 

And then it proceeds to eat the live tissue of whatever area of the body that it's been able to latch onto. And so that's what we see, is we tend to see maybe a smaller wound opening. And then as you go to explore that wound to see what's really going on there, you can usually see the larva present inside that wound cavity. 

 

Katy Starr (00:50:35): 

Right. And so I'm wondering, obviously, there's a wound on their animal, right? They're saying that it's important that we are being observant, looking at our animals, checking them over and making sure that they don't have wounds. But aside from that, are there other things like an animal, like the other one that you gave an example of, the first one that you said probably had some other issues going on, obviously, but is there, like, behavior or is there other signs of, I guess, the wellbeing of the animal, of the horse, maybe how they're acting or anything like that, that we should be looking for that has shown that this is something that's commonly seen with animals that are infected with the New World Screwworm? 

 

Dr. Gray (00:51:20): 

Yeah, there's nothing absolute. But what's usually talked about is, like, an animal may appear depressed, painful. Again, because these larvae are attacking live tissue, that tissue tends to have nerve ending. So, it should be an uncomfortable situation for the animal unfortunately. But that also may clue you in that this animal has a problem. So, it, it's not necessarily just a non-healing wound, but it may be a wound that the animal is biting at. It may be an area that the animal's showing some discomfort, a wound on a leg, that the horse may be more lame than you would expect from the size wound that you're seeing. I've seen it in the hoof, which probably had some sort of wound on the bottom of the hoof or severe thrush or something that allowed access for that worm to dig into those tissues. And so I think what I would tell people is that it's, when you see a wound, if you're in an area where Screwworm is now active, you want to be more diligent even than you might otherwise be about small wounds. 

 

Dr. Gray (00:52:20): 

Right. And really checking to see that there's no sign of maggot activity in those wounds. Keeping them covered, keeping them clean can be helpful. In terms of signs, I mean, I've seen cases where there was just blood noticed coming from the horse's sheath or when they urinated, for instance, and that was another horse that had an infestation in the sheath. They, that what they noticed was blood when the horse urinated and they thought the horse had a kidney problem or some sort of problem like that. And as it turned out, the horse had a wound and that was what was infested. So, I think the main piece for horse owners on that is you know your horse. So, if their behavior's different than it should be, just like any other medical issue with your horse, if you're seeing something that seems extraordinary or not typical, in livestock, it may be an animal that sort of separated itself from the herd. 

 

Dr. Gray (00:53:09): 

A, a young animal not staying closer to its mother. Signs that something's wrong. And those would be pretty general. And unfortunately it's not like there's something that, you know, if your horse is doing X, Y, or Z, it must be Screwworm. 

 

Katy Starr (00:53:25): 

Right. 

 

Dr. Gray (00:53:26): 

Fortunately or unfortunately, that's not the case. It's more going to require somebody observing the problem rather than thinking that they can see it from across the barn. 

 

Katy Starr (00:53:36): 

Right. One thing that we talk about quite a bit on the Beyond the Barn podcast is the importance of understanding your horse's normal. So, being able to take normal temperature, normal respiratory rate, like all those things. Knowing what the baseline is, I know it's very helpful for veterinarians when they are able to come out and help you problem solve and see what's going on. But if you're able to also understand and observe and know normal behavior for your horse, because sometimes different horses, they have different personalities, right? Some are quirky, some are a little bit more intense. Like, so just knowing what your horse's normal is, is going to be able to allow you to know when something is abnormal or going wrong. 

 

Dr. Gray (00:54:18): 

Absolutely. I think that's very well said. You know your horse better than the vet does. And you know your horse better than probably anybody else does if you're actually spending that sort of time with your horse. And so obviously an animal in pasture, as we see this fly spread north again, that's what you're wanting to watch for. You're wanting to watch for signs that something's wrong. And then keeping this particular issue on your list of what might be wrong. 

 

Katy Starr (00:54:44): 

Excellent. And so before you first saw it in person, what did you expect? And was there something that kind of surprised you that maybe you weren't expecting to happen when you first saw the initial case? 

 

Dr. Gray (00:54:59): 

I would say that I suppose I was a bit surprised at the severity of some of the infestations that I've seen. 

 

Katy Starr (00:55:07): 

Okay. 

 

Dr. Gray (00:55:08): 

At the sheer numbers of larvae that can actually be present in a wound. 

 

Katy Starr (00:55:12): 

Yeah. 

 

Dr. Gray (00:55:13): 

I find a bit shocking. Because it's not going to be typical for this to be one or two worm larvae. It's a lot. It's much more typical to see dozens or more larvae present even in a wound where you, you know, we had a case with a yearling that had an infestation in the nostril. And again, those mucocuta - what we call in medicine, mucocutaneous junctions where the skin and mucus membranes come together. Nostrils are one of those areas. So, that skin tends to be thinner and certainly if there's a small break in that skin for any reason, those are very easy access areas. And oftentimes a little bit, this particular wound was up inside the nostril. So, when at first glance, that particular filly looked like she might have a respiratory infection or a sinus infection or something because she had some discharge from her nose that was a little bit bloody. 

 

Dr. Gray (00:56:04): 

And then once you started to look into that a little more carefully, then you could see that the wound contained the Screwworm larvae. 

 

Katy Starr (00:56:10): 

I'm wondering, is it the same, like, potentially for the eyes? I know eyes are kind of one of those spots for veterinarians or like eyes are a big deal. Have you seen any in any eyes or is that something that could be a sensitive area for that? 

 

Dr. Gray (00:56:28): 

The only case that I dealt with in an eye, unfortunately, was a foal that happened to have an injury to its eye. And the, the eye was ruptured. And we actually did surgery to remove that eye. And that foal ended up being reported back to us that it did get Screwworm in that wound where the eye had been removed. I don't think the owners followed up with treatments like we'd asked them to do on that particular foal, but I don't know for sure. But we did give them things to treat that wound with and to try to instruct them how to care for it after surgery. But whether they were able to or not, I don't know. But that's the only case that I've seen in an eye personally. And that was really more what I would describe as a wound. I think that foal hadn't removed the eye would've had the same problem anyway because it was not going to heal very well. 

 

Dr. Gray (00:57:21): 

Certainly not heal with any sight in the eye because the eye had already ruptured. But ears, actually, I've seen quite a few cases. Well, I shouldn't say that. That makes it seem very large numbers. I have seen cases in, in horses' ears. Colleagues of mine did have a case like that. It was not a program I was on, but it was in Costa Rica as well. And they did have a case in an ear that they were able to clean up and that did heal nicely. And that horse, again, presented just anything that might have been wrong. A horse standing with his head down, he'd lost weight, wasn't eating well, wasn't, you know, was kind of depressed and, and standing around with his head down more than not. And he had one ear that was sort of drooping. And once that ear was examined, it was pretty obvious what the problem was. 

 

Dr. Gray (00:58:05): 

And that horse did do well with treatment. I was just working with a Native American community in Northern Panama a couple of weeks ago, and we saw several animals there with pieces of their ear missing. A good chunk of ear missing. And those on examination were doing very well. Everything looked clean. Everything looked healthy. But they were missing a big chunk of ear. And the owners told us that those were from Screwworm cases that they had been able to eliminate. So, again, I think one of the hopeful pieces of that for me was I was seeing several animals in that community where they don't have. I mean, they're extremely isolated. That's probably the most isolated community I've ever worked in. It was basically take a boat to get to the shoreline, to drive a car to drop off point, and then a five-hour hike into the community. 

 

Dr. Gray (00:58:57): 

Goodness. Yeah. So, so they've got no access to care for sure. Yeah. Yeah. And yet they're able to stay on top of some of these wounds and get these animals healed that have been infested with the screwworm. So, the takeaway from that to me was this is something, you know, certainly I, I want you to get your veterinarian involved, identifying this as the culprit, because you can't go by looks alone. There are other maggots that can be in wounds. There are, there are other blow flies that have similar looking larvae. They won't eat live tissue. They only eat dead tissue. But it's still important to have these analyzed, especially in the current state of things. This is a reportable disease. We do want people to be contacting their veterinarians. Their veterinarians will be contacting their state and local agricultural representatives so that they can report cases of New World Screwworm. 

 

Dr. Gray (00:59:50): 

We're instructing people that it's important to collect the larvae and the veterinarian, you know, there's several sources available of information now on, in American Association of Equine Practitioners website, on the USDA's website, there's some excellent materials being distributed in terms of what to do if you have a suspect case of New World Screwworm and what the veterinarian should know and do as well in terms of collecting samples. One of the, my big pet peeves is to make sure that the, you know, if you're going to start treating a wound that you suspect has New World screwworm, to make sure that you've got something topically, an insecticide on that wound topically, so that if any larvae do fall to the ground, which is pretty easy to have happen as you're cleaning these wounds, that's what the Screwworm counts on because if those larvae drop to the ground, they go into that next stage of their life cycle where they pupate, they form that little cocoon, and before they turn into flies and grow their wings, that takes place in the ground. 

 

Dr. Gray (01:00:51): 

That doesn't take place in the wound. So, once they've eaten and matured a bit, they drop out of that wound, burrow into the ground, and then mature and hatch into flies. And that process takes some time, and that varies depending on ambient temperature. If the ground, I think it, once the ground is colder than I believe like 40 degrees Fahrenheit, then it's too cold for those larvae to develop. So, winter areas, that should extremely limit the areas where this worm can actually turn into a fly. And so even when, when this was an endemic problem in the US prior to the 1950s, it was primarily confined to the Southern and Southwestern US because of that temperature limitation. And so I think, you know, that's one of the things that I, that I stress with people is if, you know, if you're going to, when you're cleaning these wounds, you don't want more flies hatching. 

 

Dr. Gray (01:01:46): 

So, try to limit that ability so you're collecting and then either, you know, destroying or burning or, or making sure that those larvae are not alive when you're done with them. 

 

Katy Starr (01:01:57): 

Well, and one thing also that I saw when I was doing some research is making sure that you don't just throw the larvae in like a garbage sack or something like that. Because there again, it could provide opportunity, I think, for it to go through that developmental stage and get to - Exactly. Where it's ultimately trying to be. That's so great though. So, obviously working with our veterinarian, like, let's all work together, make sure that we're make, you know, doing this as a teamwork, I guess, to make sure that we can help eliminate the spread of this. And the veterinarian will work to do the correct reporting for you and everything. And so then when we are working with our veterinarian, just for informational purposes, I guess, what does treatment look like? And then how do we kind of keep it from spreading to other animals that are within our herd or neighboring herds? 

 

Dr. Gray (01:02:54): 

Right. So, the fly, again, depending on ambient temperature, depending on weather conditions and all of that, has a limited range it can fly. So, if you're unfortunate enough to be in an area that has active flies, it's that diligence to make, to see that you're examining your animals, examining your herds, checking for lesions, and then treating those. Treatment in horses, there's topical insecticidal sprays for wounds, and those are probably going to be the most effective in terms of locally killing any larvae that are accumulating inside of, of a wound. And then the only systemic treatment that is currently on FDA's list of approved treatments for horses with New World Screwworm is to use a dewormer product that is able to be given as an injection. And so that is another option that can be. I do know some people that are using that orally. That's not the way that the FDA approved it, but we can do some extra label use, but this, and so still having some discussions on different states in terms of ability to move outside of an infested zone to other states, that sort of restricted movement of horses, just like any other disease outbreak, there are going to be some restrictions on moving animals from one area to another if that area is known to be infested with New World Screwworm. 

 

Dr. Gray (01:04:19): 

So, again, your local veterinarian and, and state veterinarians will have more information on what that entails. But in terms of treating your animal, again, what my approach is on these cases is sort of multi-level. I want these animals to have some sort of systemic treatment, meaning usually medications that are typically used for a deworming that do have some activity on the New World screwworm. I don't try to use those as a preventive for the most part. I think that treating wounds, so if I do find a wound and I don't have New World Screwworm, but I'm in an area that has a lot of, or pretty active cases of New World Screwworm, I want to make sure that that wound is being covered if possible to limit that fly's access to that wound. I want to make sure that that wound is covered in some sort of insecticidal spray so that the larvae aren't likely to be able to live, to eat that particular tissue. 

 

Dr. Gray (01:05:12): 

And then in terms of protecting your other animals, if you are in an area that's having New World Screwworm, you're going to have to just be that much more diligent. There's really, you know, because this is a fly, fly control systems, those can be helpful. This particular fly doesn't spend a lot of time on your horse or other livestock. It spends most of its time elsewhere and tends to only be on the animal for a very short period of time to lay its eggs. 

 

Katy Starr (01:05:39): 

Right. Okay. Excellent. So, as we start to wrap this up, and I'd love for you to add in anything else that you can think of if we haven't covered it, but from your expert perspective and experience, what key takeaways would you like to leave listeners with about the New World screwworm? 

 

Dr. Gray (01:05:59): 

I'd say, you know, number one, don't panic. First of all, what we see, especially, , for horse owners in particular, throughout the regions that are now reinfested with this problem, the percentage of cases on horses has been somewhere in the five to 6% range of cases that are being reported. So, the horse doesn't tend to be its most active host. Young animals, in particular, newborns, umbilical problems in newborns. So, that goes across species, again, because that's going to be, have some blood on it. That's going to be an area of exposed tissue that's quite prone to this problem. Anything post-castration is another big concern. And so, you know, if you see wounds, if you're in an area that has this, you know, you want to be more diligent than you were before you heard about this, because that's what that fly is going to take advantage of, are those open wounds. 

 

Dr. Gray (01:06:56): 

And so in terms of what else to be, you want to have, if you are in an area where there are active cases described, you want to have something around to treat your wounds with. Some, some of the larvicidal sprays, and there's a pretty good list on either any of those websites that I mentioned on USDA's website or on AAP's website. There's a pretty good list of products that have been approved for treatment of wounds for New Worlds Screwworm. So, some of those sprays that are insecticidal are what you want to have around if you have a large, you know, a large population of animals, especially if you've got a breeding herd or you've got a cow-calf operation or something like that, that you want to make sure that you've got something around to treat umbilical, you know, you want to treat that umbilicus on, on that newborn with something to try to prevent a problem if you're in an area that's seeing cases. 

 

Katy Starr (01:07:45): 

Right. Okay. Perfect. Thank you. And so, Dr. Gray, how can our listeners stay connected with you after this episode and kind of just keep up with what you have going on? 

 

Dr. Gray (01:07:57): 

Sure. Because now, since I'm no longer practicing, I spend a lot of time on these various projects because I'm able to, which I really enjoy. And it, it's an aspect of the horse world that we often forget about the, the working horses that are out there really, they're amazing and they, there's an unbelievable numbers of people that really do rely on them to make their lives a little bit better and provide an income stream or be able to get their kid to school or get some water to their house. And so I do a fair amount of work with the Equitarian Initiative and our website, which is equitarianinitiative.org, you can sort of see some of our projects on that. We also have a Facebook page and an Instagram page and, and all that. So, I'd say look for Equitarian Initiative on social media and you'll, you can find some of the images of these communities and these horses and that's where I'll be. 

 

Katy Starr (01:08:46): 

Awesome. And we'll be sure to include those links in our show notes so it's easy for listeners to find you guys. But Dr. Gray, thank you so much for your great expertise and insight into the New World Screwworm. And just helping us, especially as horse owners and even other livestock owners, just knowing what to look for. So, we can just, as you said, just stay diligent, make sure that we're doing our part to kind of help prevent it from spreading and just being able to protect our animals. So, we appreciate your time today. 

 

Dr. Gray (01:09:19): 

Happy to be here. 

 

Katy Starr (01:09:20): 

For horse and livestock owners, it's reassuring to know that New World Screwworm cannot be transmitted through hay or forage as current evidence tells us that it isn't a forage-born pest. At Standlee, we'll continue monitoring guidance from USDA, APHIS, and other animal health authorities, but today's recommendations remain focused on protecting animals through good wound care, daily observation, fly management, and prompt veterinary attention, not treating or restricting hay. If you have any questions or concerns that we could help address, please don't hesitate to reach out to our Standlee customer service team. I'll be sure to link that contact information in our show notes. And thanks for tuning in today. Thanks for listening to the Beyond the Barn podcast by Standlee Forage. We'd love for you to share our podcast with your favorite people and subscribe on Apple, Spotify, or your favorite listening platform. Until next time, keep your cinch tight and don't forget to turn off the water.