Screwworm: Texas declares disaster over deadly infestation

Added: 2026-06-07

[00:00:00]Welcome back to the live now from Fox.

[00:00:01]I'm your host Anna Marcic. An insect has been been making headlines this week.

[00:00:06]This insect lays its eggs and it hatches larvae that feed on flesh. Take a look at this expose coming from Bloomberg.

[00:00:13]Screwworm was eradicated from Texas in the 1970s, but this week it returned.

[00:00:20]For the first time in nearly 60 years, a devastating agricultural insect has entered the United States. The USDA has confirmed the first domestic case of this flesh-eating New World screwworm in a South Texas calf, which has triggered an emergency 12-mile quarantine zone in that Texas county. And this is putting the state's $15 billion cattle industry on high alert. So, joining us to break down what exactly the screwworm is and its threat to livestock and pets is Dr. Sonya Swiger. She is a veterinary entomologist with Texas A&M University.

[00:00:56]Thanks so much for joining us here on live now from Fox.

[00:01:00]>> Thank you. Happy to be here.

[00:01:01]>> So, first of all, let's just break down what exactly this New World screwworm is and the threat that it poses to livestock.

[00:01:09]>> Yeah, so like you said earlier, it is a fly and it's a parasitic blowfly and it lays eggs on wounds of animals or any type of opening or orifice that it has access to and then those larvae will hatch off and start eating on the flesh of that animal.

[00:01:27]>> And when it eats this flesh, I I mean, like does it just eat away at the whole animal?

[00:01:32]>> Well, I mean, since it's fly larvae, it is a little tough for them to eat and consume an entire animal, but they will feed on it and make wounds very grotesque in the sense. And And what really ends up happening is the animal doesn't survive these infestations. So, normally the animal will pass before full consumption by the larvae, but the impact is severe while they're there and while they're feeding.

[00:01:55]>> So, on your screen right now is a a video, a picture of this screwworm. And we noted that it's a fly, but it's called a screwworm. Why why is that?

[00:02:07]>> Yeah, you know, that was a term that was given to it back in the you know, probably 50s, 60s. I'm not 100% sure when they started calling it that, but it's because of the appearance of this maggot, so to speak, right? So, um it has these unique striations, which are actually spines that circulate the body, and then the way it feeds with the mouth hooks down, they kind of have a screw-like appearance in a pattern by the way they're feeding in the flesh.

[00:02:31]>> So, we know this first case was just recently confirmed in Texas. How did this screwworm come from Central America into the United States?

[00:02:39]>> Yeah, unfortunately, it began moving out of South America through Central America and up into Mexico um a couple years ago, right? We've been watching it since 2002 22 or 2023.

[00:02:51]Um but most of that movement is due to moving of animals that were infested with these larva. Um and when you move those animals without treating them ahead of time, it can lead to further infestations in other areas.

[00:03:04]>> What do we currently know about the scope of this South Texas infestation, and what exactly are veterinarians there looking for inside the quarantine zone?

[00:03:14]>> Yeah, you know, I'm I'm not there on the ground with the folks because I do work for A&M, and we're more educational on our side, but the the agencies in charge, which is Texas Animal Health Commission, are implementing what was put into the playbook by USDA-APHIS. So, there's partnership between both of those agencies, and they're currently conducting quarantines and restrictions and animal inspections, which is the surveillance part of it, in addition to searching and looking for adult flies as well outside that quarantine zone, and also releasing those sterile flies to hopefully eradicate very quickly back out of Texas.

[00:03:50]>> And releasing those sterile flies is essentially how screwworm is treated, right? What's the science behind that?

[00:03:57]>> Yeah, you know, that it's a really cool story because it's started so long ago.

[00:04:02]But previous entomologists, way before my time, Dr. Niplin, Dr. Bushland, developed this procedure in which we sterilize the males in a sense with the radiation. And then when we release them, they were they mate with the wild females and it prevents them from being able to lay fertile eggs. So, they basically lay unfertilized eggs and that approach leads to the decrease of the future generations of those flies that we would have from them.

[00:04:27]>> So, how quickly does the screwworm spread among cows that are impacted?

[00:04:34]>> Um that's I love that question. I'm not sure if I really know the full answer because, you know, I have personally never dealt with screwworms in my lifetime cuz they've been gone longer than that.

[00:04:44]Um but, you know, it it really depends on the population size of the adult stage. So, the infested animal that was identified can't share that to another animal. So, you're not getting infestation sharing between maggots.

[00:04:56]It's just whether or not adult populations get a chance to basically take hold in an area and then they'll start laying their eggs after a few they're a few days old and then it can get more problematic if we don't react to it.

[00:05:10]>> And, you know, as we just saw the return of screwworm this week, um is there a need to be worried across the United States that this can spread and become a bigger issue?

[00:05:20]>> Um you know, there's a need to be concerned and understand that this is something that's happening. Um I wouldn't panic. I wouldn't get too, you know, too out of normal behavior for most folks, especially if you're in northern states. Um but, we definitely, you know, people in Texas, anyone that's closely to close to the border near Mexico, uh we want them to, if they're not already, start looking at their animals on a more regular basis to prevent any infestations to go unrecognized, but if you're in other states, it's more right now just learning about it and understanding what this impact is just in case, but hopefully it doesn't get to that point that we have to worry about in other states.

[00:05:59]>> And why is it so fatal if it's left untreated?

[00:06:03]>> Um cuz the maggots don't really care if the host doesn't survive, which is a rare thing for most parasites anyways, but they'll start feeding and a lot of times that feeding is occurring in parts of the body that are very problematic, right? So, we've had incidences that this one was related to the umbilicus and when you go up the umbilicus, that's a direct shot to the abdomen of that animal. Um there's also incidences of infestations in the in horns when after dehorning and that's of course, you know, going to be a straight shot to the head, which as you might imagine is very problematic. Um so, that's why it can be very impacting, but on top of that, there could be a secondary infection that comes in, maybe toxicity to the feeding process or sepsis. So, there are other ways the animal can succumb to these infestations.

[00:06:46]>> Let's talk about pets. There are a lot of dog owners out there, a lot of cat owners out there. Do they need to be worried? Can this impact their pets?

[00:06:54]>> Uh definitely. Um especially if you're in an area, um if you know, I don't know if we have anybody listening from outside the United States, but if you're in an area, you definitely need to be concerned if the screwworms have returned in that area and in that area of Texas right now, we do want to watch our pets. We want to look at them just as much as we would our livestock because yes, they will infest animals.

[00:07:13]Uh dogs seem to be high on the list right now out of Mexico, not as high as cattle, but still over 5,000 have been um identified as having infestations and that's a large number.

[00:07:23]>> What are the signs and symptoms that pet owners can look out for um if they're worried that their pet pet might be showing signs of illness?

[00:07:31]>> Um I mean, obviously it would have to be in an in an area where it's at, right?

[00:07:34]But if you do see maggots, it's the same thing with livestock. You're going to see the maggots feeding on a wound on the animal and any maggot feeding on an animal is never a good idea and never a good thing to have happen.

[00:07:46]>> Is this Does it pose a threat to humans?

[00:07:51]>> Yes, even humans have to be concerned.

[00:07:53]It is rare in humans and even rarer in birds. We get asked a lot about that, too. Right now it's like a 1% or so or less of the population of the cases they've recorded that impact humans, but we still we want humans to be aware it is a possibility.

[00:08:09]I wouldn't put high on your list, but we still want them to realize that it is it can happen. We've had cases of it over the last several decades of travelers going to places where they still can get into where they still find new world screwworms and then coming back to the United States with infestations.

[00:08:28]>> And just talking about the spread, screwworms can't fly more than 12 miles on their own is what I read, but they can cover huge distances if they're inside a host. How does that maybe complicate the the quarantine and the containment strategy?

[00:08:43]>> Yeah, that's why most of that quarantine and containment is around animal movement. And that's the first part of it is you want to go and inspect those animals. You don't want them to get out of that area prior to an inspection and treatment because that's the fastest way for them to move. And yes, flies can can fly, right? That's why they have wings.

[00:09:03]But that definitely would not be as long of a distance as we can move an animal in just a few hours. So >> And as we know, there has only been one reported case so far in the Texas calf.

[00:09:14]Do you see this becoming something bigger? I mean, what are what are things that the researchers should be looking out for right now?

[00:09:21]>> Yeah, I mean, yes, only one case so far has been reported.

[00:09:25]You know, we hope that that will be the only one and that all the efforts that are on the ground right now and with the release of the I believe it's 8 million sterile flies right now are being released in that area.

[00:09:36]That hopefully will put this at bay and we won't see many cases outside of this one if any at all.

[00:09:43]>> Awesome, Sonia. Thank you so much for your time and your expertise here on live now from Fox. We really appreciate your time.

[00:09:48]>> Thank you so much.