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Michael Dunne: Whether you're a voracious carnivore or a dedicated vegan, you're still affected by the national and state cattle industry, given its impact on so many aspects of our society. Today on the show, you'll hear from the person in charge of keeping Oregon cattle free of a re-emerging parasite that, left unchecked, could wreak havoc on cows in every corner of the state. Dr. Ryan Scholz is Oregon's state veterinarian. Thanks so much for coming on and talking with us.
Ryan Scholz: Absolutely. Thanks for having me.
Dunne: Let's start with this: Describe what New World screw worm is and what it does.
Scholz: Yes. New World screw worm is a parasite that infects livestock, or really any warm-blooded animal. In its most basic sense, it's the larva of a fly. It's commonly called a maggot, but it's a fairly unique fly. It's native to South America. It was once present in the U.S. We eradicated it as a country back in the late 1960s, and then over the next 20 to 30 years progressively pushed it south through Mexico and Central America and back into South America. A control program was established in Panama, and since then we've been free of it. Now it's making its way back. The unique thing about this maggot, or screw worm, is that instead of consuming dead tissue, which is what most of the bot flies and maggots we have here natively in the U.S. do, it consumes live tissue. The flies lay their eggs on the edge of wounds, and the larvae essentially screw, or burrow, into the tissue and can cause fast tissue destruction. They can create very large wounds very quickly.
Dunne: If an animal is infected with this parasite, can it be fatal?
Scholz: It can, if it's not treated. The thing to remember is that this is a parasite, not a virus, so it's treatable, and it's fairly easy to treat if it's caught early. That's one of the reasons we're trying to get the word out: so everyone keeps it in the back of their mind, and if they see something, they say something. That way we can get it diagnosed, start treatment and save the animal, and prevent further infestation in other animals. The last thing we want is for those larvae to complete their life cycle, drop off the animal, pupate and create more flies that lead to more infestations.
Dunne: What would the symptoms be? How would someone know if livestock they own has it?
Scholz: Often it's wounds that progress quickly. It's an animal that looks off and is declining fairly rapidly. These wounds often progress over three to five, maybe seven days. They develop a strong odor and become very large, and the animal looks like it's in a lot of pain. A lot of what we've seen out of Texas, and previously in Mexico, involved umbilical lesions. So in newborn calves or other livestock, the larvae get into the umbilical cord, and you'll see a calf that's doing really poorly, with a swollen abdomen. That smell is something we rely on in veterinary medicine. You can often smell that something's wrong before you can see it, and that's the case with a lot of these infections too.
Dunne: How quickly can it spread through a herd?
Scholz: It depends. Right now it's confined pretty much to an area of South Texas, plus one case in New Mexico, right on the Texas-New Mexico border. Even within that area, every one of those cases, and there are 12 at this point as of when we're talking, has involved a single animal in a herd. If you catch it quickly, you can stop it in that animal, because this isn't a disease, it's a parasite, and it has to complete its life cycle. Depending on climate, that life cycle takes about 18 to 21 days, from when a fly lays its eggs to when those eggs mature into adults that can lay eggs themselves. So if you catch one infested animal quickly, we can stop it there. If we don't catch it, that's where it can perpetuate and become a much bigger problem. That's what a lot of this response is about: it's here in Texas, we know it's there, but we're working to stop those infestations quickly so they don't multiply and spread further.
Dunne: You mentioned it can affect other warm-blooded animals. Could humans be affected by this too?
Scholz: They can, and they have. The first case associated with this outbreak in the U.S. was actually a human, several months ago. That person wasn't infested in the U.S.; they came from a country where the infestation is endemic. But yes, humans can be affected. The major difference is that people tend to notice something crawling in a cut faster than you might notice it on a cow roaming a couple hundred acres. Most of the time when people are infested, they notice it quickly, get treatment quickly, and it's taken care of right away. With animals, it can often get missed in the early stages.
Dunne: Could it spread to native wildlife like deer and elk?
Scholz: They haven't found it in any deer or elk in Texas right now, but in Mexico and South America it's very common in wildlife. Part of the theory behind why we're seeing it spread as much as we are is that it's likely affecting some wildlife species down there, and that's probably contributing to the spread.
Dunne: If you're just joining us, we're talking with Dr. Ryan Scholz, the state veterinarian here in Oregon, about the New World screw worm. How do you stop the spread? What steps are necessary?
Scholz: The biggest thing, and the way we eradicated it as a country back in the 1960s, was through what's called the sterile fly technique. Most flies, and this one in particular, only mate once in their life cycle. So the idea is that if you flood an area with sterile males, the overwhelming likelihood is that wild females will mate with a sterile male during their one-time mating, and then lay eggs that are sterile and don't hatch. It's a long-term control method, and it's what the USDA is doing a lot of right now in Texas: releasing large numbers of sterile flies. You may have seen some of the news coverage; there's a facility being built and converted at the top of Mexico, and an Air Force base in Texas is being converted into a facility for sterile fly production, so they can produce the numbers needed to control this outbreak. Beyond that, at a more localized scale, it's more about control than eradication. The only way to actually get rid of it is through sterile flies, but we can control it until we get to that point. For individual owners, that means surveillance: keeping an eye on your animals, and if you notice something's off or something seems wrong, contacting your veterinarian to come examine it, and letting us know so we can investigate and treat it if needed. On a more local scale, if we have a case here in Oregon, we have a state response plan that involves state and federal agencies coming in to treat the animals on that farm. This is an infestation, not a disease, so we can treat it. We'd also put movement restrictions around the area and do surveillance to make sure we don't have more cases nearby, and control any additional cases we find.
Dunne: You said we'd eradicated it back in the 1960s in this country. Any idea how it came back?
Scholz: This is something we've been watching and preparing for over a number of years. The control program established after it was eradicated, which pushed it down through Panama, was maintained over the Darien Gap, the narrowest part of the Panamanian isthmus, where sterile flies are consistently released. There were probably some illegal livestock movements through that area, and that breached the control zone, which was really established to control natural encroachment of the fly. There are checkpoints and other measures the U.S. and Panamanian governments collaborate on, but they're not perfect. Once it got past that point, it moved into larger areas and has been slowly encroaching north, through natural spread and the movement of livestock. Frankly, we've been expecting this for a while. A lot of us thought we'd see it in the U.S. sooner than we did, which means we've had more time to prepare. Response plans at the state and federal level have had more time to mature, and we have a lot of those resources available now, including the sterile flies, which are already in process and well underway.
Dunne: Any impact to the food system? I know it's still small in Texas right now, but is that a concern?
Scholz: No. This is an external parasite, and it's something we can treat easily. It's not a food safety issue. Food remains safe, even from an affected animal. After treatment and the required withdrawal period, an infested animal can still be used for food production.
Dunne: There have been reports about funding cuts throughout the federal government. Has the Department of Agriculture been affected, and does that raise concerns for you, at the state level, about funding to help eradicate this?
Scholz: Funding is always going to be a big part of any disease response. There's actually been a lot of funding dedicated to this response specifically, so it's happened somewhat outside of the other political issues at the federal level. I'm not involved enough in that to speak to it in depth, but what I can say is that real resources have been poured into this response at the federal level. A lot of work has been done, a lot of people are dedicated to it, and a lot of funding has gone toward it. So no, I don't think funding cuts have had a significant impact here.
Dunne: As the climate has changed and gotten warmer, are conditions now better for the screw worm? Does that mean our climate here in Oregon is more conducive to it than it might have been 50 or 100 years ago?
Scholz: Maybe on a small scale. This is a tropical fly, and its home range is in tropical areas. If you look at the historical eradication maps, the northern half of the U.S. was never really listed, because we eradicated it every winter, as soon as we got a hard freeze. This is a tropical fly; it doesn't survive hard freezes. So I don't think it significantly changes the picture for New World screw worm. There were cases of it in northern climates, including Oregon, but we never had sustained populations because of our hard winters. On a national scale, the line marking where we'd eradicate it every year versus where we do now may have shifted north somewhat. The USDA updated some of the plant climate zones in the last couple of years to reflect that. In individual years, winters that are colder or warmer than historical norms could affect whether we get rid of any infestations in a given year. If this had happened a year ago here in the Willamette Valley, given that it didn't get all that cold this past winter, we might have seen a few more cases survive the winter than we normally would. But on a grand scale, I don't think we can say we're definitely going to have a worse problem just because it's a few degrees warmer than it was 50 years ago. It can survive during this time of year pretty much anywhere, if it's transported there.
Dunne: Doctor, my last question for you: What signals from Texas would tell you the challenge has passed? Is the hope that they'll simply find no more cases, or is this more of an ongoing effort, regardless, to keep cattle herds safe?
Scholz: Unfortunately, Texas is kind of the tip of the iceberg right now. If you look south from Texas, this has been slowly encroaching through Mexico, so even if Texas can eradicate it by flooding the area with sterile flies, we'll still have cases happening just south in Mexico. We're going to continue seeing these encroachments. It will really take a concerted effort by U.S. states, the federal government, the Mexican federal government and Mexican state governments working together, the way we did back in the late 20th century, to push this worm back down past the Darien Gap. This is something we'll be dealing with, at least in the back of our minds, for quite some time, until we can produce and release enough sterile flies to push it back south. Whether that means seeing expanding cases here in the U.S., or holding it to just Texas with occasional encroachments, I don't know. But I think this is going to be a long-term, slow-simmering response, at a minimum.
Dunne: That's Dr. Ryan Scholz, the state veterinarian here in Oregon. Doctor, I really appreciate you coming on to talk about this important issue.
Scholz: Absolutely. Thank you for having me.
Dunne: Now let's check in with our reporter about the McKenzie River floodplain. Karen Richards is a reporter here at KLCC. Karen, great to see you. Thanks so much for coming in.
Karen Richards: Absolutely.
Dunne: I really enjoyed your story about the McKenzie River floodplain. What did you learn? Talk about it.
Richards: What I found interesting was a couple of things. I'd only started hearing about it after the Holiday Farm Fire, because after that area was burned and devastated, you'd see the heavy machinery off to the side, and I heard the first stories about what crews were trying to do there. But this project had actually been in progress well before that. In fact, they learned things from the fire that they hadn't anticipated: some of the projects they'd already been working on, widening the river and creating more wetland area, actually helped slow some of those fires in ways they hadn't expected.
Dunne: That's one thing I learned. Can you explain, for folks listening, why they're doing what they're doing?
Richards: It all started with a paper. I don't remember the exact year, but this is all fairly new territory. Researchers had learned there was a theory that if you restore rivers closer to what they were before people narrowed them, for industry and to put roads alongside them, since you don't want a river carving its own course and covering a road every so often, the system becomes healthier. People made these rivers very deep and narrow, but that's not how rivers want to be. So if we widen some of the channels that feed into the McKenzie, the McKenzie itself stays as it is, but the tributaries feeding into it get wider and can chart their own course during a storm or other high-water event. That's healthier for everything, from water quality, since the water can filter through silt, to the fish, which now have places to hide instead of being stuck in a deep, fast torrent. It's been an ongoing effort across several locations. I was able to see a few in different stages of construction, which was fascinating, and it seems to be working.
Dunne: I know you're not a construction expert, but how are they doing it? You mentioned massive machinery out there. Is it basically just moving a lot of earth and restoring a path for the water?
Richards: Right. It's what they call cut and fill: they cut out some of the dirt and fill it into other places to create the new contours where the water will find its way around. They've left some trees standing, though the fire did go through there, so crews had to take out a lot of trees. There was a campground in the area that the Forest Service decided wasn't worth reopening, so they're using that whole site and turning it into a basin. Yes, it's a lot of heavy equipment, and a lot of people question whether that's environmentally unfriendly, but the theory is that over time, any fuel used or short-term damage the trucks cause is outweighed by the benefits that come from the project.
Dunne: I imagine it's not just a matter of moving a lot of dirt. This is a pretty complex project, isn't it?
Richards: Oh, absolutely. There's all kinds of engineering involved. They have to widen some of the bridges that currently span these narrow bits of water, because if the channel is going to spread out, the bridge needs to span a larger area. They did one like that at Quartz Creek, and it'll be the same at this new site I mentioned. So there's major construction, a lot of engineering, and a lot of on-the-ground decisions, like leaving a particular spot alone because there's a thriving little ecosystem there, or a beaver they don't want to disturb.
Dunne: Did the fire, in some ways, make this project easier, since a lot of trees got burned and out of the way? Did that create a bit of a path for them?
Richards: A pathway, maybe, but it also gave them a lot of logs to build the log jams that help the water find crevices and pools. They needed a huge amount of material, and for good or bad, the fire gave them plenty of it. Even a burned log works fine, and it leaves carbon in the system. That material was something they would have had to source from somewhere anyway, so the fire ended up providing thousands of logs for these projects.
Dunne: Karen, my last question for you: From talking with the people doing this project, do you have a sense of how different it will look if we're driving up Highway 126 in five or 10 years?
Richards: From Highway 126 itself, it might not look that different. But if you take a couple of the side roads up to some of the creeks they've been working on, on the way to Cougar Reservoir, and look at one today versus in five years, it'll be very different. It'll be more like a wetland. At the one we visited at Finn Rock Reach, we had to walk quite a way in to reach an island in the middle of the area, and there are already willows towering tall after just three years, along with all kinds of other evidence of change.
Dunne: Interesting. That's fascinating. Karen Richards, reporter for us here at KLCC. Thanks so much.
Richards: Absolutely.
Dunne: That's the show for today. All episodes of Oregon on the Record are available as a podcast at klcc.org. Tomorrow on the show, we'll learn about new ways to help veterans dealing with PTSD. I'm Michael Dunne, host of Oregon on the Record. Thanks for listening.
