Earlier this month, Texas Gov. Greg Abbott advised residents to brace themselves for an “extraordinarily challenging summer.” A flesh-eating parasite that did lots of of tens of millions of {dollars} of injury throughout the state in the Sixties and ’70s, one which had been thought of eradicated from the US for many years, has come again and poses a critical menace to cattle, wildlife and pets.
The first case of New World screwworm on this newest outbreak was confirmed June 3 in a 3-week-old calf in South Texas that has since recovered. But regardless of enhanced surveillance and restrictions on motion, instances proceed to flip up lots of of miles past the southern border.
If the parasite’s advance can’t be halted by the state and federal governments’ stepped-up surveillance, containment and remedy efforts, specialists say, the outbreak may price the southwestern United States alone billions of dollars.
The larvae of the parasitic fly feed on the tissue of any warm-blooded animal, even people, however officers say the threat to folks is low. While it’s not a direct meals security subject, the infestation may elevate the price of beef at a time when Americans are already paying record high prices.
The newest outbreak began in Central America in 2023 and has been in depth, according to the US Centers for Disease Control and Prevention. There have been greater than 185,000 animal instances and a pair of,100-plus human instances reported in Mexico and Central America.
In the US, there have been 15 instances recognized as of Sunday, in accordance to the US Department of Agriculture. Cattle have been affected most to this point. Other animals which have been infested embrace sheep, goats and a canine. Texas, the largest beef producer in the country that produces the most beef in the world, has had the majority of instances. The canine lives in New Mexico.
No human instances have been reported as a part of this outbreak. The final case in the US was a travel-related one in Maryland in 2025.
The CDC has designated the outbreak a Level 3 public well being emergency, its lowest degree, which suggests the CDC is actively monitoring the scenario and utilizing its specialists to handle the occasion. The company has additionally been urging medical doctors to be on the lookout and report any instances.
The title of the pest could confuse folks, stated livestock entomology and parasitology expert Dr. Jonathan Cammack. It’s a fly, not a worm. It’s not even a contagious disease that spreads from animal to animal; it’s an infestation.
It’s referred to as a screwworm as a result of, in contrast to many fly larvae that feed on useless or decaying flesh, New World screwworm larvae screw into the flesh of warm-blooded animals to feed.
Emory Cushing, an entomologist with the USDA’s Bureau of Entomology, and Walter Patton, a scientist at the University of Liverpool in England, first identified New World screwworm as a definite species of fly in 1933.
Scientists used to name it solely a screwworm. But in the Nineteen Eighties, when the species turned up in North Africa, a area that had its personal distinct screwworm, scientists wanted a means to distinguish between the two, stated Cammack, an assistant professor and the state extension specialist at Oklahoma State University in Stillwater.
Scientists named the fly generally present in Central, South and now North America the New World screwworm and labeled the form discovered extra sometimes in Africa and Southeast Asia the Old World screwworm.
The New World screwworm makes warm-blooded animals sick when the grownup feminine deposits eggs into an open wound or a mucous membrane, like in the eye or nostril.
The eggs hatch inside about 12 to 24 hours. Larvae emerge and immediately start to feed, tearing into the host animal’s tissue, inflicting sores to broaden and deepen and generally creating secondary bacterial superinfections, according to the CDC.
The odor that comes from the deterioration in the animal’s flesh can even appeal to extra screwworm to lay extra eggs, and it might appeal to different species of fly that may co-infest the lesions.
Larvae can rupture arteries, inflicting extreme bleeding and leaving the animals severely anemic.
If left untreated, screwworm infestations can finally kill the animal host within seven to 14 days.
If it’s caught early, animals may be cured of a New World screwworm infestation.
Veterinarians sometimes clear out seen eggs and larvae after which use an insecticide that kills larvae and protects in opposition to reinfestation.
In August, the US Department of Health and Human Services issued a declaration permitting the US Food and Drug Administration to present emergency use authorizations for animal medicine to deal with and stop infestations of screwworm. There are a handful of medicines to deal with and stop infestations in pets and in livestock, zoo and wild animals.
Animals that absolutely get better from an an infection can finally enter the meals provide after a rigorous USDA security inspection.
Just as a result of one calf is sick doesn’t imply the whole herd will get it, Cammack stated.
“It takes a lot of very specific steps to happen, so it’s not like this is just going to pervasively spread through any of our herds of animals,” Cammack stated.
To management infestations, the authorities has inspired producers to preserve an in depth eye on their animals and look ahead to wounds that might make the animal a goal.
But that might not be as straightforward because it sounds. Wounds as small as tick bites can appeal to the flies. Although it might be straightforward for an individual with one pet cow in the yard to preserve an in depth eye on their animal, greater operations like these in Texas face a harder job. “We’ve got producers on the other end of the spectrum that could be interacting with their animals two or three times a year,” Cammack stated.
Before it was eradicated in the Sixties, screwworm induced enormous livestock and wildlife losses, principally in the hotter states, with infestations concentrated in Texas, Mississippi, Alabama, South Carolina, North Carolina, Georgia and Florida. Cattle producers in affected states misplaced up to $50 million to $100 million per yr earlier than full eradication, in accordance to a 2025 analysis from the USDA.
In the 1950s, scientist Edward Knipling found that he may sterilize flies with radiation. Female New World screwworms mate solely as soon as, and Knipling theorized that if he created sufficient sterile flies for the females to mate with, the fly inhabitants would die off.
In 1958, the US created its first fly-rearing facility in Florida and dropped sterile flies in affected areas. By the subsequent yr, outbreaks in Florida, Alabama and Louisiana were controlled. Building new sterile fly production facilities in the Southwest helped eradicate the flies in that area too, and by 1966, the US was declared formally screwworm-free.
Some outbreaks nonetheless cropped up in the US after that – the largest in 1972, when Texas alone had 90,000 instances – however specialists say the effort was past profitable.
“Using the sterile insect technique was one of the USDA’s major achievements of the 20th century,” stated Max Scott, an entomology and plant pathologist who’s a professor at North Carolina State University. “The USDA, over a 50-year period, succeeded in eradicating this fly all the way down to the Panama-Colombia border.”
The screwworm barrier in Panama finally failed. The newest outbreak began in 2023, with a number of instances popping up in Panama and Costa Rica, after which slowly began spreading north towards the United States.
The unfold occurred for just a few causes, Scott stated.
In hindsight, he stated, the pressure of infertile male flies used not too long ago was “probably not as good,” so the feminine flies had been now not selecting to mate with the less-fit sterile males.
A current surge of migrants throughout the Panama-Colombia border additionally included animals that will have been contaminated, he stated. The fly doesn’t journey large distances and strikes extra ceaselessly on infested livestock. Livestock was additionally smuggled throughout borders with out correct well being checks, in accordance to a 2022 report from the suppose tank InSight Crime.
USDA Secretary Brooke Rollins has blamed the Mexican authorities for not cracking down on “cartel trafficking and immigration” whereas some Democrats level the finger at the USDA for not doing sufficient.
In a letter to the USDA on June 9, a number of US senators expressed issues that “significant staffing reductions” due to retirements and resignations, in addition to Trump administration funding and staffing cuts, affected the nationwide screwworm response. Rollins has repeatedly denied that staffing cuts had an impact and says President Donald Trump has given her all the sources she’s wanted.
Even some Texas Republicans have been vital of the Trump administration’s response. Texas Agriculture Commissioner Sid Miller critized the federal government’s efforts as “slow, bureaucratic, and incomplete.” He needs the federal authorities to use a focused chemical baiting methodology as a bridge earlier than extra sterile fly amenities may be constructed.
Although the screwworm infestation has created “unfortunate circumstances,” Rollins stays “bullish and buoyed and inspired and just invigorated by these incredible producers that we’re up there fighting for every single day, and we’re going to beat this,” she stated June eleventh. “We beat it before, and we’re going to beat it again.”
The US is taking a number of steps to cease the screwworm.
The USDA has invested tens of millions to modernize a facility in Mexico that produces sterile flies. Rollins says that facility ought to open this month and complement the flies already produced in Panama. The USDA additionally broke floor on a $750 million fly-producing facility in Texas, however that’s not supposed to open till subsequent yr.
As of now, the USDA is bringing 100 million flies from its Panama facility to affected areas in the US each week.
The company can be looking for approval for the NovoFly, a genetically altered all-male fly that might create stronger flies sooner, however the US Environmental Protection Agency has not stated when it might determine whether or not to approve the fly.
The Biden administration closed southern borders to Mexican cattle in November 2024, after the first screwworm case was confirmed in Mexico, however after strain from the beef business, Trump briefly reopened the border to cattle imports in February 2025. The USDA shut southern ports to Mexican cattle once more in May 2025. As of June, exports of horses, pigs, ferrets and birds had been halted from all US states to Mexico by the USDA.
The USDA has staged sniffer canines to search for screwworm at the southern border and elevated Tick Rider border patrols — horseback riders on the lookout for the pest.
“We now know what the enemy looks like. We now understand what we have to do,” Rollins stated final week.
The USDA has briefly relocated its Iowa lab crew that works with screwworm to Kerrville, Texas, to deliver testing nearer to the affected space. The company additionally launched a $100 million innovation initiative to incentivize scientists to give you extra methods to get rid of screwworm. The USDA has announced funding for a few of these new approaches, together with utilizing drone know-how, creating novel traps and lures, and creating genetic strains to produce flies sooner.
Several states have additionally taken motion to cease screwworm. New Mexico stepped up its surveillance, and a few states together with South Carolina and New York have created interstate motion well being restrictions for warm-blooded animals coming into from impacted areas. California is working with the University of California, Riverside to conduct prevention trapping and has sought emergency use authorization for added therapies.
And in Texas, the state with the most instances, Abbott expanded a catastrophe declaration to authorize the use of all state authorities sources to reply to screwworm instances, a number of counties have achieved the similar. The state has arrange extra surveillance and created infested zones whereas implementing quarantines, motion controls and surveillance in affected areas. Texas has additionally developed a free course to broaden the variety of New World screwworm inspectors throughout the state.
The state authorities is working carefully with personal landowners to do extra fly trapping in areas frequented by Texas’ considerable wildlife. With about 5.4 million whitetail deer alone, deer searching provides about $9.6 billion to the state’s financial system, stated Alan Caine, wildlife division director with the Texas Department of Parks and Wildlife,
Abbott inspired ranchers and others in the state to pay shut consideration to their animals and to report any instances shortly.
“Texas is resilient. Our producers, veterinarians and state officials are among the very best in the United States. It is critical to stay vigilant and stay informed. We prevented and eradicated this before; we can do it again.”