The New World screwworm has arrived in the United States.

For years, ranchers across Southern states have prepared for a potential invasion of the flesh-eating parasite that can wreak havoc on livestock, pets and even humans. 

Though the United States went decades without a confirmed case of the invasive pest, it’s now made its way across the U.S.-Mexico border. Officials have confirmed one case in a New Mexico dog and five cases in Texas, including cattle, a dog and a goat. 

The New World screwworm poses potentially life-threatening risks to pets, wildlife and livestock. While the risk is concentrated in a few states, experts say a massive invasion could ripple across the American economy through higher grocery prices.

Is it a fly or a worm?

Contrary to its name, the screwworm grows into an adult fly that’s about the size of a common housefly. The adult fly has orange eyes, a metallic blue or green body, and three dark stripes along the back. 

The name screwworm refers to the larvae (maggots) that burrow into open wounds, feeding as they go “like a screw being driven into wood,” according to the U.S. Department of Agriculture.

The maggots burrow into the flesh of living animals through wounds as small as a tick bite or in body openings such as the eyes or nose. That means ranchers must keep close watch over newborn calves with exposed umbilical cords and may need to rethink branding and tagging operations that could provide an entry for the pests. 

What to look for 

The screwworm can infest livestock, pets, wildlife, birds and, in rare cases, people.

Infested animals can exhibit foul-smelling wounds with visible maggots as well as lesions in navels, ears or other sites. Texas A&M says animals may bite or lick at wounds and could display unusual restlessness or lethargy. 

“Pay attention to your animals, pay attention to any wildlife that might be around your property, if they’re acting like they’re in distress,” New Mexico Livestock Board Executive Director Belinda Garland told Source New Mexico this week. “Be aware, but there’s no need to panic.”

The federal Centers for Disease Control and Prevention says people may feel or see maggots moving within a wound, or in their ears, noses, eyes or mouth. The larvae can cause painful sores that worsen within a few days. People may also experience bleeding and a foul-smelling odor from the site of the infestation. 

People should immediately see a healthcare provider, who must remove each maggot, sometimes surgically, the CDC says. 

For animals, USDA has approved emergency use of several medications for prevention and treatment of the parasite. Those include ivermectin, the drug that many people hoarded for off-label use during the coronavirus pandemic. 

Will this cost me?

The New World screwworm could raise prices at the grocery store. In fact, it probably already has: American beef prices are near record highs after ranchers liquidated herds to the smallest level in 75 years because of drought and other operating disruptions, including a halt on cattle imports from Mexico. 

In an effort to stop the screwworm, the U.S. banned live Mexican cattle imports, which traditionally occupy American pastures and feedlots before going to slaughter. Last month, David Anderson, professor and extension specialist in livestock and food product marketing at Texas A&M University, told Stateline that the move likely exacerbated meat prices. 

Beef prices have increased faster than inflation in recent months, according to the most recent consumer price index report. While ground beef prices fell 1.27% in May, that drop followed a 2.7% increase in April, CNBC reported, and beef prices remain up 12.9% year over year.

The pest could also impact dairy supplies, according to the University of California Agriculture and Natural Resources. While ranchers can hold back cattle during an outbreak, dairies may be forced to dump milk during an outbreak. 

What’s being done to stop it?

USDA has created screwworm monitoring, reporting and quarantine protocols for animals. But because the disease does not create food safety concerns, the agency will not stop any movement of animal products, including meat.

To eradicate the flies, the federal government plans to breed sterile male flies and then release them into areas with established populations. The sterilized males will mate with females, which will then lay unfertilized eggs. With females mating only once in their lifespan, officials say this method progressively reduces and eliminates the fly population.

USDA just broke ground on a $750 million sterile fly facility in Edinburg, Texas, that aims to produce up to 300 million sterile flies per week when it opens next year. The agency has also invested in sterile fly facilities in Mexico and Panama.

Political blame game

The arrival of the screwworm has ignited political attacks from Washington, D.C., to the Southern border.  

At a U.S. Senate oversight hearing earlier this week, Minnesota Democratic Sen. Amy Klobuchar raised concerns about how deep cuts to USDA employment affected the department’s ability to combat issues such as the screwworm threat. She noted that the department’s Animal and Plant Health Inspection Service lost 25% of its staff, including more than 300 veterinary services employees. 

The Trump administration has sought to deflect blame on previous President Joe Biden. 

In that same hearing, Agriculture Secretary Brooke Rollins blamed the previous administration and Mexican cartels’ “refusal to crack down” for allowing the screwworm to migrate north. 

“Everyone took their eye off the ball years ago, and unfortunately, because of the border policies, it’s coming our way,” Rollins said.

Meanwhile, Texas Agriculture Commissioner Sid Miller has called on the federal government to deploy targeted baits that kill screwworm flies before they reproduce. Miller recently lost his GOP primary for reelection.

“The science is settled. The tools are available,” Miller said in a news release this week. “What’s missing is urgency from the USDA.”

Stateline reporter Kevin Hardy can be reached at khardy@stateline.org.

WASHINGTON — Agriculture Secretary Brooke Rollins on Wednesday blamed the Biden administration’s “open-border policies” for the six confirmed cases of the New World screwworm that have reached the United States, repeating a theme among Republicans.

Speaking to members of the Senate Agriculture, Nutrition and Forestry Committee during an oversight hearing, Rollins said it was the previous administration as well as Mexican cartels’ “refusal to crack down” that allowed the New World screwworm fly to migrate north.  The pests can be transported via infested livestock or pets.

“Everyone took their eye off the ball years ago, and unfortunately, because of the border policies, it’s coming our way,” Rollins said.

According to Rollins, there are now six confirmed cases of the New World screwworm in the U.S., with five in South Texas and one in New Mexico.

The New World screwworm is a devastating pest that can wreak havoc on cattle herds and other livestock. The screwworm is a type of fly that spreads by laying eggs in other animals, with the eggs then hatching into larvae that will eat the animal’s flesh, causing significant harm and even potential death, according to the Centers for Disease Control and Prevention. 

The fly had been eradicated in the U.S. since 1966. 

USDA staff reductions

Throughout the hearing, committee members and Rollins agreed on the importance of working to eradicate the screwworm in the U.S. 

But some Democrats said recent Trump administration decisions could hinder the department’s ability to carry out that task.

Sen. Amy Klobuchar, D-Minn., voiced concerns about the impact of recent layoffs at the U.S. Department of Agriculture on the department’s ability to combat issues like the screwworm threat. She noted that the department’s Animal and Plant Health Inspection Service lost 25% of its staff, including more than 300 veterinary services employees. 

“Clearly, we need a long-term response,” Klobuchar, the committee’s ranking member, said. “I continue to be concerned about some of the reorganization’s cuts to USDA. How that could affect our long-term response.” 

Since President Donald Trump returned to office last year, the USDA has lost more than 21,000 employees, according to data from the Office of Personnel Management. It ranks among the largest decreases of any federal department or agency. 

But Rollins reiterated that the staff dedicated to preventing the spread of the screwworm has actually increased. At the beginning of last year, she said, the USDA had 10 full-time staff members working on screwworm prevention, while it now has more than 120. 

She said the department has allocated $1.3 billion to combat the screwworm. 

“We’re prioritizing where the big threats are as we’re working to ensure that we’re meeting all of the needs across the country,” she said.

During the hearing, Sen. Roger Marshall, R-Kansas, also pointed the blame toward the Biden administration. 

“We saw this coming under the previous administration, and they refused to respond,” he said. “When you let millions of people migrate through Central America this way, we saw the screwworm just come with them — whether it was on their pets or maybe they were bringing livestock.”

USDA slowed screwworm spread

The agency’s internal predictions, according to Rollins, were that the screwworm, which is still widespread throughout South and Central America, would have reached the U.S. by last summer. But she said the department was able to slow the devastating pest’s arrival by closing all ports across the Southern border to livestock trade last summer. 

USDA is primarily combating the spread of the New World screwworm by breeding and releasing sterile screwworm flies, which will limit the number of flies that can reproduce and ultimately reduce the population. 

She said the U.S. currently produces about 100 million sterilized flies a week, but needs to increase its production to 500 million a week to eradicate the fly. 

But Rollins stressed that while the screwworm poses a threat to U.S. livestock, particularly cattle herds, it doesn’t risk tainting the food supply itself. 

“The food supply is 100% safe,” she said. “This is not a disease. It’s not a virus. It’s a fly.”