New World screwworms (NWS) are now only dozens of miles from Texas’ southern border.
DALLAS — Because Collin County rancher James Foster has 200 head of cattle, his eyes are glued on the southern border with Mexico, watching the slow, northward advance of a parasitic pest that could devastate the livestock industry in Texas.
“We’ve got some place where we have cattle that have a lot of brush on them, some larger acreage places. And there are some cattle, we may not see them for a few days. And if that was to get started, they multiply so quickly, and they do so much damage so fast that you could actually lose livestock to it,” Foster explained on Y’all-itics.
New World screwworms (NWS) will feed on any mammal, even pets and humans. But they prefer livestock.
NWS flies lay eggs in open wounds. Those eggs then hatch into larvae, aka maggots, which feed off the flesh with sharp hooks in their mouths. And that’s what makes these flies different. Typically, maggots will consume dead or dying tissue. NWS prefers live tissue.
It sounds horrific, and that’s why ranchers and the Texas Animal Health Commission (TAHC) are taking the threat very seriously.
“What we’re concerned about is that this is a foreign animal pest of great economic concern. Not only does it cause pretty significant detriment to the animals, but it causes a lot of economic loss not only from potential death loss, but increased production costs associated with inspection and labor and treatment costs,” Dr. Thomas “TR” Lansford said.
Dr. Thomas “TR” Lansford is TAHC’s deputy executive director and assistant state veterinarian.
When Texas last suffered through an NWS infestation in the early 70s, the impact was substantial. Lansford tells Y’all-itics that, in terms of today’s dollars, it costs the overall Texas economy around $1.8 billion.
An outbreak can spread fast if it takes hold, and that’s because infected animals can move long distances over short periods of time. And NWS is currently marching north from Mexico.
TAHC says the current closest case is around 79 miles from the border. The closest it got over the past several weeks was 62 miles, but that case is currently inactive.
The number one way to address an NWS infestation is by fighting the flies with… more flies, sterile flies to be precise. Texas, along with the U.S. Department of Agriculture, built a sterile fly dispersal facility at Moore Air Base in Edinburg, Texas, earlier this year.
Sterilized male flies are released from the facility to mate with females. And that’s the key. Female NWS flies only mate once in their lifetime, and after breeding with a sterile male, they’ll lay nonviable eggs. That will naturally decrease the population over time.
The big problem now, however, is that the Edinburg facility won’t be fully operational until November 2027, when it’s expected to produce 300 million sterile flies per week. Until then, the USDA is producing sterile flies in Panama.
Meantime, TAHC is taking a “three-legged stool” approach that includes surveillance, trapping efforts along the Texas-Mexico border, and movement controls.
“It’s not that we are not going to allow any animals to move, it’s just that there’s going to be a process that includes inspection, treatment, identification, and permitting just so that we know that they have been through the process and we’re doing everything we can to not move infested animals,” Dr. Lansford from the TAHC explained. “But given the situation in Mexico, we expect to have to deal with New World Screwworms at some point. Now, when that is, I can’t guess that.”
In the meantime, James Foster, the Collin County rancher, tells us the best way Texas ranchers and animal owners can prepare and protect themselves.
“You’ve got to be very diligent in inspecting your animals. And you just have to really keep an eye on things. And if you do see something, you need to report it. Take a sample and report it,” Foster said.