Ranchers are anxiously watching for news on the New World screwworm, a parasitic fly that was a major pest in Texas the 1960s. The screwworm lays its larvae in the wounds of live mammals, which then burrow down into the host. These wounds are painful and can even be fatal.
By the 1970s, insect experts pushed the flies all the way south to Panama. But in recent years they’ve started to head north again, and are now about 370 miles from the southern border.
The U.S Department of Agriculture is investing millions to fight the advance of the fly for the sake of the state’s ranchers. But of course it’s not just livestock that are at risk – the parasite could pose problems for wildlife, too.
Marcus Blum, assistant professor and wildlife specialist at the Texas A&M AgriLife Extension service, spoke to the Texas Standard about the potential impact on wild animals.
This transcript has been edited lightly for clarity:
Texas Standard: Can you give us some examples of wildlife that might be particularly susceptible to the New World screwworm?
Marcus Blum: Absolutely. I think the most obvious one, or the one that people are going to think about the most, is going to be white-tailed deer. But not just white-tailed deer, predator species. In reality, it’s any warm-blooded animal, although mammals seem to be the particular focus of this parasite.
At this point, is it assumed among people in your field that the screwworms will get here, it’s just a matter of when?
I don’t think it’s assumed. USDA and Mexico are working really hard, and other groups are working diligently, to keep the fly from continuing to spread north.
So at this point, we’re not assuming that it’s going to get here. We’re just trying to prepare everybody in case it were to get here to think about the potential impacts.
Well, let’s talk about those potential impacts, because I think the focus started on the beef and the cattle industry because of its economic importance. But an economic impact could happen from a wildlife perspective, too. What might that look like? I guess, worst-case scenario.
Yeah, so a recent study by Natural Resources Institute, Texas A&M, and AgriLife Extension found that just the white-tailed deer industry alone in Texas is valued at over $9 billion.
So, I mean, it really just depends on the reduction in populations that we see across the state for how much that might be reduced. But, I mean, it’s realistic to assume that it could be millions, even billions of dollars.
Again, that really depends on just how much of populations are hurt, and that it’s going to expand into other wildlife species as well, including predators, non-native wildlife like exotics, which is a $2 to $3 billion industry as well. There are pretty large or pretty significant impacts that can occur here.
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I guess if we’re thinking about the biological landscape in Texas now versus when screwworms were last here 50 to 60 years ago, is there a big difference, or what are you thinking about?
I like to go to whitetail because that’s going to be one of the species that’s mostly on people’s minds. But we were probably a little less than half of our current population – we’re over 5 million whitetails deer estimated in Texas, and in the ’60s, it was probably around a little over 2 million deer.
So one, we have a lot more deer on landscape. We have a lot of more exotics on landscape as well.
But it’s not just the number of mouths on the landscape for the flies to infect, but also these animals are facing increased challenges from habitat fragmentation all across the state as people move out of urban environments and into more rural; everybody wants their little ranchette in Texas.
And so we’re seeing increased fragmentation. So there’s a lot of new challenges on the landscape for wildlife.
I imagine, for cattle owners, they’re checking on their herds regularly. But what about for landowners and wildlife? Is there anything they can do to help monitor for screwworms?
Absolutely. You kind of hit it on the head right there: It’s about monitoring regularly. And so what we’d ask people is to try and monitor wildlife regularly.
And there’s a lot of ways we can do that. Hunters are going to be extremely helpful during this for Texas Parks and Wildlife and other agencies. But aside from hunters, we can use trail cameras, and those don’t even have to be during hunting season.
You could use security cameras for urban environments. People watching wildlife in their backyard at feeders and things like of that nature – lots of opportunities there. If you have high quality optics, that’s always going to be the best way to observe wildlife.
Don’t get too close. We will practice safe-viewing distances. But yeah – cameras, trail cameras, optics, those are all great. Doing your wildlife surveys, if you’re involved in any wildlife management plans with Texas Parks and Wildlife, that’s always going to be super helpful as well.
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