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Hosted by members of the University of Minnesota Extension Beef and Dairy Teams, The Moos Room discusses relevant topics to help beef and dairy producers be more successful. The information is evidence-based and presented as an informal conversation between the hosts and guests.
Welcome to The Moos Room. It's a lovely day in Western Minnesota again. We've actually been getting some rain, which is definitely a blessing. We had some early drought, and I was worried about how the pastures were gonna grow. But now, of course, like usual, they're out of control. We got so much grass.
We're probably gonna bale some of our pastures just to keep ahead of it. You know, we've been
Our cows are being supplemented this summer. Kind of made the decision to decide to do some supplementation on our organic cows on pasture. We used to go kind of grass-fed for the whole summer, but I don't know, it suffers reproduction. The cows are a little bit less in body condition score. So our cows are doing well.
They're milking well on pasture, but kind of decided that, well, maybe we need to keep the repro up, and I've probably kept around more cows than what I've wanted just because we haven't been able to get things pregnant in the summer with going all grass-fed. So that's always the challenge. But one thing I wanted to talk about today, and I've not really talked about this on the podcast at all.
I wanted to talk about it briefly is New World screw worm. It was found in the US this past week in Texas in a three-month-old calf in Zavala County, Texas, so along the Texas-Mexico border. And it was, uh, identified in the umbilical area on this calf. And so I wanted to talk a little bit about what it is, how to identify it.
I know at least those of us that listen up here in, in the northern parts of the US maybe think, "Well, it's not... It's in Texas, we don't have to worry about it." But I think it's one thing certainly to know about and what's happening with it here in the US. So it's endemic in some states and countries in South America.
It's endemic in Cuba, Dominican Republic, and it's been in the US before. And they used some sterile insects in the 1960s, and it was eradicated from the United States in 1966. So 60 years ago, or well, 70, 80 years ago, it was, uh, eradicated. But it did come to head in 2017 in Florida in the Keys. So way on the southern tip of Florida, there was a small outbreak there, but it was successfully eliminated with these sterile flies, and we'll talk about the sterile flies as well.
But wanted to talk about some things to look for and what, what to think about
So I think the thing is, is that it's not really just another fly. Obviously, it is flies, and we've talked about eradicating flies on this podcast many times. But the problem with this fly is this New World screw worm in the larval stage of the fly actually burrows into live tissue, and that's what really makes it a threat to other livestock and even people.
So this fly is about the size of a housefly, so
we would recognize it as just another fly that we see. But really, this fly or pest can really spread through the movement of livestock or wildlife, pets, vehicles, and maybe even people. And I think the problem that has come about with this is that it's really difficult to identify in early stages, so that's been the challenge and why it's been difficult, uh, to help find and eradicate.
So how can you identify this? Well, if you really wanted to look at flies, and I've done a lot of looking at flies around in our pastures and can actually do pretty good about identifying some of the flies, uh, that we see in our pasture. So here, this New World screw worm, they ha-- as a fly, they have red eyes, they have a shorter center stripe down their body, and they have a metallic blue-green body, and have a yellow-orange face.
So that's how you can maybe identify it a little bit more with definite red eyes and kind of a yellow-orange face. But the larvae is tapered at both ends. It's pale with kind of dark spine bands that you can see, and it has a dark rear at the, at one end
So why is this screw worm a little bit different? So it's kind of unlike other flies that feed on manure or spilled feed or other rotting tissue. These female New World screw worm flies, they target live animals. So they lay their eggs around wounds and other vulnerable areas and lay about two to three hundred eggs at a time.
So kind of like this calf that was found in Texas, a vulnerable area, umbilical cord areas, it can lay its eggs there. So within twelve to twenty-four hours, these eggs hatch into larvae that actually burrow into the living tissue and begin eating it. So the larvae actually have kind of hook-like mouth parts, and they tunnel deep into the tissue, which creates severe wounds as they grow.
So obviously, as the, these larvae feed, the wound gets much bigger. It starts to smell a lot. It can get really infected, cause severe inflammation and pain for the animal. So other people have described it as being very painful to an animal because it creates abscesses when they're burrowing in, when the eggs hatch and the larvae start feeding
So this New World screw worm is kind of considered an infestation rather than an infectious disease. It doesn't spread directly between animals, and it's not really considered a food safety concern. So it's, it's not contagious and doesn't really pose any issues. But it spreads when a screw worm fly lays its eggs in a wound and not really through the meat, dairy, or poultry products
So what are the signs that maybe some producers we shouldn't ignore? Obviously, it's difficult. It can be difficult. Some of the same symptoms that you see. So it's actually you have to observe it. If you're checking your animals every day, you might think about a heightened awareness for some specific signs.
Some of these warning signs include an animal that's uncomfortable or agitated, they're head shaking, tail swishing, kicking at the body. Obviously, these animals are gonna isolate themselves from the herd because they're not feeling well. You know, their flesh is getting eaten by this larvae. They have open wounds or sores that kind of worsen.
They get bad really quick, and they start to smell. So you start to get these foul-smelling lesions that get much larger very quickly. And then you can see some abscesses around rather than one signal wound, because the, as the larvae eats, they're creating abscesses. And you might be able to see a visible larvae within the wound.
I think that's probably the true tell sign is you can see these larvae within a wound, and you'll see lots of different abscesses that they create. And they can be from small pea-sized or large ones. And you'll usually see more than one And really the first 24 to 48 hours, so one to two days, can be challenging because the larvae can be hard to detect.
But as they grow, you'll be able to see that
So APHIS, or the Animal Plant Health Inspection Service at USDA, has put out some fact sheets on New World screw worm. Obviously, the current risk is very low, but they have a nice fact sheet out that addresses some of the myths and misconceptions about New World screw worm, and we can talk about them. I think one of the big things is that the myth is that it can spread from animals to people and person to person And it's not contagious.
It doesn't spread directly from animals to people or from person to person. So the infestation begins, like I said before, when the female fly lays eggs in a wound. The eggs hatch into larvae that burrow deep within the wound and start feeding on the living tissue About seven days later, the larvae drop to the ground, burrow into the soil, and then you get a pupa, and then a new fly emerges from the soil about seven to 54 days, depending on temperature and humidity.
So these female flies mate after three days, and the males can mate within 24 hours of maturation, and the cycle continues. So this is why it's very important to find the infestation if, if you suspect it or if you're in the southern US to be watching for this
Another myth is that if you find infested animals, the whole world
Another myth is that if you find an animal that's infested, the whole herd must be culled, and that's not true. So culling is not going to be used to manage herds in which cattle are infested
So obviously if there is a suspected case, the herd will be placed under a hold order and not allowed to move animals until they're examined for New World screw worm. So the cattle will be treated or animals will be treated and quarantined until all wounds heal and there's really no evidence of reinfestation after 21 days.
So it's basically quarantining animals and making sure they get, and treating them and making sure they get over this Another myth, infested animals must be destroyed and can't enter the food supply. Well, that's false. Animals that have recovered from an infestation can enter the food supply if they meet all regulatory requirements, just like any other animal has with quarantines and no residues in the product
Another one is that New World screw worm does not cause respiratory illness or coughing. Obviously, we're looking for open wounds, foul smells, and irritated behavior on the animals, and we see that in lots of different cases
So here's another myth. It says that it would spread rapidly through the United States like it seems to be moving in Mexico. Well, the fact is, New World screw worm does not spread rapidly and would not spread rapidly in the United States. And why th- might that be? Well, screw worms thrive in tropical and subtropical climates.
They don't tolerate prolonged periods of very dry, hot or very cold weather, and it doesn't spread between animals, and infestations are easy to recognize. So rapid spread in a country due to humans moving infested animals could happen. So I think trying to find it and treat it is one of the big things to do first.
So in the past, they used sterile insects to fight New World screw worm And it's a proven method pr- preventing the spread
So they have female New World screwworm flies that only mate once in their lifetime. So when they mate with a sterile male, they lay unfertilized eggs that don't hatch. So you release sterile flies outside of the affected areas and hope that they would go in and m- mate with them, and then they have eggs that never hatch And the sterile insects is safe.
It's happened before. That's how they've eradicated it in the United States 50 years ago
So there are some other treatments that can be used, especially from an emergency situation. Ivomec or ivermectin is, can be used in an emergency sit-si- in an emergency situation to treat them. Dectomax can, Negasunt powder. So there's a few things, and especially Ivomec and Dectomax, we know quite well within the cattle industry, they can be used in an emergency basis to treat them
But really treatment includes cleaning and getting rid of the larvae in the wounds, and then using some conditionally approved and emergency use products, which can limit the damage as long as producers know how to use them. And then obviously inspecting animals throughout every few days to be able to look at that
There's no vaccine that's out there to prevent these flies, but obviously, you know, we've talked about our horn fly vaccine before. I think MedGene is trying to develop a vaccine that can be used for the control of, of these New World screw worm flies to help prevent the life cycle from happening. So I think there's a lot of work happening with this, and only the future will tell what, what might happen.
Obviously, it comes down to a lot of surveillance and trying to track animals and quarantining animals and treating animals, and early detection and reporting and treatment will be critical in kind of keeping this pest contained. And obviously, we're trying to do everything that we can to help prevent more spread here within the US.
So anyways, hopefully you learned a little bit about New World screw worm and what it is. I know I haven't talked about it before, but I thought I'd just give an idea, quick idea to people about what it is and what it may be happening here in the US from that standpoint. So with that, if you have any comments, questions, scathing rebuttals, uh, feel free to contact me at The Moo's Room.
That's T-H-E-M-O-O-S-R-O-O-M @umn.edu or contact me on the web, University of Minnesota Livestock Extension or UMN WCROC Dairy. And with that, hopefully you have a good week. Bye.