The Flesh-Eating Fly Heading North: Why Wyoming's Hunting Community Is Watching Texas With Dread
For most hunters who have spent years saving preference points, logging backcountry miles, and booking expensive guided trips into Wyoming's high country, the threat of a parasitic fly that eats animals alive from the inside out sounds like something out of a horror novel. But as of early June 2026, the New World screwworm is no longer a distant abstraction — it's a confirmed, active infestation inside American borders, and the men whose livelihoods depend on the health of Wyoming's elk, mule deer, and bighorn sheep are paying close attention.
On June 3, 2026, the USDA confirmed, in Texas, the first U.S. animal case in the current outbreak of New World screwworm. That single calf in south Texas triggered a chain reaction of alarm across the ranching and hunting industries — and is now sending ripples as far north as Wyoming's Absaroka Range and the Wind River backcountry, where outfitters guide clients into some of the most remote big game terrain on the continent.
What the Screwworm Actually Does
The name alone is enough to make your skin crawl, and the biology behind it is every bit as brutal as it sounds. The New World screwworm, known scientifically as Cochliomyia hominivorax, is an obligate parasitic fly whose larvae invade and consume living tissue, causing myiasis with severe consequences for human health, animal welfare, and agricultural productivity. Unlike scavengers that feast on the dead, this parasite needs a living host — the warmth of a living body is the environment in which the larvae thrive and feed.
The name screwworm refers to the maggots' feeding behavior as they burrow into the wound, feeding as they go like a screw being driven into wood. The flies are attracted to open wounds, including tick bites, where they lay hundreds of eggs. Those eggs hatch into larvae, which feed on living tissue to complete their life cycle. The larvae cause extensive damage by tearing into the host's tissue with sharp mouth hooks, and the wound can become larger and deeper as more larvae hatch and feed on living tissue. Secondary bacterial infections can also occur as a result of an infestation.
Newborn animals, animals that have recently given birth, or animals that have suffered an injury are most vulnerable. The flies may also be attracted to antler bases after shedding and mucous membranes. That vulnerability calendar maps almost perfectly onto Wyoming's fawning and calving season. Newborn fawns and calves are especially vulnerable because the moist umbilical area can attract flies and create ideal conditions for screwworm infestation.
From Panama to Texas: How a Contained Pest Became a National Crisis
The screwworm's return to American soil didn't happen overnight. It has been building for years, fueled by a combination of ecological pressure, inadequate containment capacity, and tragedy. Although eradicated from the United States in the 1960s through the sterile insect technique (SIT) and contained thereafter by a Panama-based biological barrier, the parasite remains endemic in parts of South America and the Caribbean. That eradication was one of the great triumphs of American agricultural science — but it required constant, active maintenance to hold the line.
In 2023, outbreaks of NWS began spreading north through Central America and Mexico again. Cases quickly increased in Central America, expanding to Costa Rica, Nicaragua, Honduras, Guatemala, Belize, and El Salvador. In November 2024, NWS was detected in a cow at an inspection checkpoint in Chiapas, Mexico, and progressive northward spread has been confirmed in Mexico since that original detection.
The sterile insect technique — the primary weapon against the pest — works by releasing massive numbers of factory-reared, sterilized male flies into the wild. Because female screwworm flies typically mate only once, a mating with a sterile male produces no viable offspring, eventually collapsing the wild population. A facility specially designed to breed and sterilize screwworms in Panama releases 100 million sterile flies every week, but more factories will be needed to stop the spread as the parasites continue to migrate north through Mexico. Then came a devastating setback: the NWS prevention program suffered a tragic blow in June 2025 when a plane carrying sterile flies crashed in southern Mexico. Both Guatemalan pilots and a Mexican agronomist engineer were killed.
To prevent the infection of cattle in the U.S., cattle imports from Mexico were halted in May 2025. The border closure bought time, but the fly didn't stop. The New World screwworm fly now threatens the $113 billion U.S. cattle industry for the first time in more than a half century, with an infestation confirmed in south Texas. The infestation was discovered in a single three-week-old calf in La Pryor, Texas, about 100 miles southwest of San Antonio and 50 miles from the U.S.-Mexico border.
Texas as a Warning Sign: What's Already Happening to Hunters and Outfitters
The economic and operational fallout in Texas has been swift and measurable. Concerns over the spread of screwworm in Texas are extending beyond cattle ranches and into the Rio Grande Valley's hunting industry. Just days after the first screwworm case was confirmed in Texas, the number of infected animals increased, raising fears among ranchers, hunters, and hunting outfitters about the potential impact on wildlife populations and future hunting seasons.
Joshua Lopez, owner of Quacker Smackers Outfitters in Alton in south Texas, said the threat of screwworm is already impacting the Valley's hunting industry. Lopez said the threat of screwworm is already hurting businesses, adding that a fellow outfitter already saw a 30% drop in calls. The damage isn't just speculative — it is arriving in real booking numbers before a single wild deer in the region has been confirmed infected.
Some hunters are hesitant to book trips because they are worried about encountering infected animals or harvesting game that may be vulnerable to the pest. "Scared that animal that they shoot, for example, we got wild hogs at the moment to come hunt, they might be a little bit scared that the screwworms can be living in that hog," Lopez said.
The challenge for wildlife managers is stark: ranchers can closely monitor livestock, but wildlife such as deer and feral hogs roam freely, making it more difficult to detect or contain an outbreak. There is already concern in Texas that an emerging screwworm infestation in cattle will spread to wildlife. Texas outdoorsman Barrett Liquori, who manages white-tailed deer herds on vast ranches, told Cowboy State Daily that the information environment around screwworms has been plagued by rumor. "I really don't know what to think about it at this point. There's so many unknowns," he said. "We face drought, we face flooding and hard winters, all of which can kill deer. This is just one of those things. We don't know yet whether to be scared of it." But Liquori didn't dismiss the historical precedent either, adding that "back in the 1970s, the screwworm was a thing in Texas. And they beat it, at the cost of many lives — livestock, horses and deer."
In Texas, outfitters say clients have already started cancelling previously scheduled fall hunts over concerns about screwworms spreading to wildlife. Texas Parks and Wildlife Department law enforcement spokeswoman Maggie Berger captured the scale of the governmental response when she noted her agency was "currently responding to service calls due to flooding and severe weather in multiple areas of the state as well as much time being dedicated to the new world screwworm response."
Wyoming Looks North — and Inward
The Industry's Current Read on the Threat
For now, screwworm doesn't seem to be on the Wyoming outfitting and hunting community's radar, said Dustin Stetter, of Dubois, president of the Wyoming Outfitters and Guides Association. That relative calm, however, is not the same thing as confidence. "If it does get up here, it's going to be awful," Stetter told Cowboy State Daily. Stetter's assessment wasn't born of panic — it came after consulting with people who know the biology of the parasite intimately. He said he's spoken about screwworms to a neighbor who is highly knowledgeable about the subject and was given a stark picture. "Any mammalian species can get it. If it gets into your wildlife, it doesn't care," Stetter said.
That indiscriminate reach is exactly what separates the screwworm threat from a disease that might target a single species. This parasite does not respect the careful management categories that wildlife biologists spend careers maintaining.
The Backcountry Vector Problem
One of the most specific and underappreciated risks in Wyoming involves the very infrastructure of backcountry hunting itself. If outfitters unwittingly took infested pack horses or mules deep into the backcountry, that could spark an infection in elk herds. Wyoming's guided hunts frequently involve mule strings carrying camp equipment, meat, and hunters into wilderness areas that can take multiple days to access on horseback. An infested animal introduced into that environment, far from any veterinary care, could establish a beachhead in herds that have no prior exposure and no natural resistance.
Other big game species would probably be of top concern. "The two most vulnerable herds in Wyoming are mule deer and bighorn sheep," Stetter said. That assessment reflects a hard ecological truth. Mule deer and bighorn are already struggling against disease outbreaks, habitat fragmentation, and other stressors. Screwworm would be "just one more thing" threatening them, Stetter said.
The bighorn sheep concern is particularly acute. These animals occupy high, remote terrain that is difficult to access for treatment or monitoring. A screwworm infestation in a bighorn population could quietly devastate a herd before managers even became aware of the scope of the problem. Wyoming's bighorn herds already contend with respiratory disease outbreaks linked to domestic sheep — piling a flesh-eating parasite on top of existing immune challenges would stress these populations to a degree that could take decades to recover from.
What the USDA Says Hunters Stand to Lose
The federal government has been blunt about the consequences for the hunting community specifically. The USDA's Animal and Plant Health Inspection Service issued guidance making clear that screwworm is not merely a rancher's problem. Deer and other species are vulnerable to NWS infestation, which can reduce the number of fawns that survive and grow into adults. Untreated infested animals will die, leading to smaller herds, fewer tags, and more restrictive seasons.
The downstream consequences for hunters extend beyond the immediate loss of animals. Compromised meat quality, deformities on hides and antlers, and stunted growth and reduced antler development are all documented outcomes of NWS infestation — which means that even animals that survive an encounter with the parasite may be permanently diminished in condition and trophy quality. For hunters who have invested years of preference points and thousands of dollars in an archery elk tag in the Thorofare or a mule deer hunt in the Winds, that kind of degradation in the resource is a gut punch that transcends economics.
Additional surveillance or control activities could lead to closed hunting areas and reduced game, and wildlife management organizations could require additional physical check stations for game inspection. State and federal agencies may restrict live animal, meat, or carcass transport across county, state, and international lines to prevent spread and protect livestock and wildlife. For a non-resident who has flown into Jackson or driven fifteen hours to hunt Wyoming and harvested a bull on day six of a nine-day trip, a restriction on transporting a carcass across state lines is a logistical crisis on top of an ecological one.
A Pest With Historical Precedent — and Historical Scars
The screwworm is not a new problem for America — it is a returning one. NWS was eradicated from the United States in 1966 using the sterile insect technique. That eradication campaign was one of the most ambitious and successful programs in the history of American animal agriculture, and it required decades of sustained scientific effort, international cooperation, and biological manufacturing capacity at enormous scale.
The last time the United States saw an animal screwworm case before this current outbreak was a small episode in the Florida Keys. Local ranchers are concerned that the fly will spread among wildlife, particularly deer, as a small, short-lived outbreak did in the Florida Keys in 2016. That episode was contained partly because of the island geography of the Keys — a fortunate accident of topography that does not apply to the open rangeland of south Texas or the continuous wilderness corridors of the American West.
The federal response to the current outbreak has been substantial. In August 2025, USDA Secretary Brooke Rollins announced the largest initiative yet in the department's plan to combat NWS at the Texas State Capitol alongside Governor Greg Abbott. The announcement built upon USDA's five-pronged plan issued in June to combat the northward spread from Mexico into the United States. The construction of a domestic sterile fly production facility was announced to ensure the United States continues to lead the way in combating the pest. Despite those investments, the parasite crossed the border anyway.
The Feral Hog Question
One of the more nuanced dimensions of the screwworm threat in the context of Western hunting involves feral hogs. In states like Texas, the possibility that screwworms could devastate feral hog populations has a certain dark appeal — hogs are invasive, destructive, and largely despised by landowners and wildlife managers alike. It would be "a good thing" if screwworms infested hogs and killed them, but it's inevitable that the infestation would spread to other wildlife. The parasite does not function like a targeted intervention. It is an equal-opportunity destroyer, and the same fly that kills a hog will lay eggs in a fawn, a bighorn lamb, or an elk calf with equal efficiency.
Wyoming does not have the feral hog problem that plagues Texas and much of the South, but the logic applies in reverse: the absence of a convenient "acceptable" host species in Wyoming means screwworm would have a direct and immediate impact on the big game animals that define the state's hunting identity and economic value.
The Business of Wyoming Hunting — and What's at Stake
Wyoming's guided hunting industry is not a casual enterprise. Outfitters operating under the Wyoming Outfitters and Guides Association run licensed operations offering elk, mule deer, bighorn sheep, whitetail, antelope, bear, and other species to clients who travel from across the country and the world. Many of these operations work the same wilderness blocks year after year, building relationships with wildlife populations that represent the product they are selling. The health of those populations is not just an ethical concern — it is the balance sheet.
The cost of a top-end guided elk hunt in Wyoming can run well into five figures when you factor in outfitter fees, licenses, travel, and gear. Hunters invest years in the preference point system just for the opportunity to draw a tag in a premium unit. Texas outfitters are already worried that a screwworm outbreak there could ruin their hunting season, and Wyoming outfitters and hunters say if the infestation hits here, it would be a wildlife disaster. The difference between the Texas situation and Wyoming's potential exposure is largely one of geography and time — not biology.
Stetter acknowledged the tension between vigilance and alarm, noting that the industry has grown accustomed to navigating threats to wildlife. "It's best not to assume worst-case scenarios," he said. "We've gotten alarmist regarding that sort of stuff because of existing threats to our wildlife." That measured tone reflects the pragmatism of men who have spent careers managing risk in wild places — but it also reflects an honest acknowledgment that Wyoming's game animals are not operating from a position of strength heading into this potential new threat.
An Already-Stressed Wildlife System
The screwworm concern arrives in Wyoming at a moment when the state's wildlife managers are already fighting on multiple fronts. Chronic wasting disease has been advancing steadily across the state's deer and elk populations. Wyoming Game and Fish Department tested 5,370 samples from elk, deer, and moose in 2025, and CWD was detected in 842 of those samples. CWD prevalence averaged 21.6% in hunter-harvested mule deer bucks, up from 19.4% in 2024, while the percentage in hunter-harvested white-tailed bucks was 32.1%.
Mule deer and bighorn are already struggling against disease outbreaks, habitat fragmentation, and other stressors. Adding screwworm to that equation — a parasite that targets precisely the newborns and injured animals that represent each year's recruitment into the population — would compound the pressure on herds that are already demographically stressed. The cumulative effect of CWD attrition on adult animals combined with screwworm mortality of fawns and lambs could produce population declines that licensing reductions alone would be unable to address quickly enough.
What Hunters and Outfitters Should Be Doing Now
Awareness is the first line of defense. The USDA has been emphatic that early detection and rapid reporting are critical to any containment effort. USDA urges residents in the area to check their pets and livestock for signs of NWS, to look for draining or enlarging wounds and signs of discomfort, and to look for screwworm larvae and eggs in or around body openings, such as the nose, ears, and genitalia or the navel of newborn animals.
For outfitters specifically, the risk management calculus centers on their pack strings. Any horse or mule being transported from an area with known or suspected screwworm activity should be inspected thoroughly before entering Wyoming's backcountry. State and federal agencies are collaborating to protect wildlife, domestic animals, and people from NWS, but boots-on-the-ground awareness in remote areas will ultimately determine how quickly an incursion is detected.
Hunters heading into the field anywhere in the screwworm's potential range should also understand what they are looking at when they approach harvested or live game. A wound that appears unusually wet, enlarged, or infested with larvae — particularly in an area near the nose, ears, genitals, or umbilicus of a young animal — warrants immediate reporting to state wildlife authorities. Infestations by NWS maggots can cause painful, foul-smelling wounds in animals and people. If not treated early, they can lead to extensive tissue damage and potentially death.
The Long View: A Fight America Has Won Before
The screwworm's eradication from the United States in the 1960s stands as one of the defining achievements of American agricultural science. The sterile insect technique, which underpins that eradication and the ongoing containment effort, remains one of the most elegant pest control methods ever developed — a biological intervention that requires no chemicals, no habitat disruption, and leaves no residue in the environment. It works. The problem is scale and speed: the fly is moving faster than the sterile insect infrastructure can currently match.
The USDA's announcement of a domestic sterile fly production facility signals a long-term commitment to rebuilding that capacity inside American borders, rather than depending entirely on the Panama facility and international cooperation. "All models showed New World Screwworm entering the country in 2025; however, thanks to the hard work across the entire Trump administration and our industry, state, and local partners, we were able to buy time for this moment. Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action," said Dudley Hoskins, Under Secretary for Marketing and Regulatory Programs.
For the hunters and outfitters of Wyoming, that long institutional view is cold comfort when fall seasons are months away and the threat is already established on American soil. The calculus right now is simple: the screwworm is in Texas, it has demonstrated an ability to move, and there is no natural barrier between the Rio Grande Valley and the Wind Rivers that a fly cannot cross. The men who guide elk hunts out of Dubois, manage mule deer herds in the Red Desert, or pack clients into the Beartooths on horseback are watching Texas the way a rancher watches a storm building on the horizon — not certain it will arrive, but certain they need to be ready if it does.
