Five new screwworm cases found in Texas, New Mexico

U.S. officials confirmed three new New World screwworm cases on June 9, bringing the total number of domestic cases to five. The infections were found in multiple Texas counties and a dog in New Mexico, reviving fears of a wider outbreak that experts say could

Five more screwworms aren’t just a headline in Texas and New Mexico — they’re a signal that the insect is moving through living animals again.

On June 9, U.S. officials confirmed three new cases of the New World screwworm, a parasitic fly that infects animals through open wounds. That brought the total number of domestic cases to five from last week, extending the threat beyond where the first U.S. detection was reported.

The newly confirmed cases were found in: two calves in Zavala County, Texas; one calf in La Salle County, Texas; one goat in Gillespie County, Texas; and one dog in Lea County, New Mexico.

Experts warn that if the insect spreads widely, the damage could reach far beyond farms. A widespread outbreak could devastate wildlife and cost Texas $1.8 billion in economic damage, including possible higher beef prices because of infected cattle.

Beef prices have already been moving upward since December 2020, driven by strong demand and the smallest U.S. cattle herd in 75 years, according to the American Farm Bureau Federation. Now, the renewed screwworm risk adds another pressure point to a market that has not had much room for shock.

New World screwworms are roughly the size of common houseflies and have advanced across Mexico and Central America since 2023, according to the Centers for Disease Control and Prevention. The first U.S. case was found in Texas on June 3.

Screwworm flies cause myiasis — a flesh-eating infestation — when larvae burrow into living tissue. The fly’s name comes from how its maggots screw into open wounds using “its sharp mouth hooks. ” according to the Animal and Plant Health Inspection Service. The USDA says the parasite infects only living livestock. wildlife. birds. pets. and. in some rare cases. humans. and does not infect meat or fruit.

The fly’s advance has come in waves. The CDC said new cases were reported in October 2024 in Panama. Costa Rica. Nicaragua and Honduras. fueling concerns that the insects could spread north to the United States. The USDA also said the first case in southern Mexico was reported to the United States in November.

The renewed threat is not just biological — it is also political and economic. On June 5, Canada’s Food Inspection Agency announced it was banning Texas livestock because of the screwworm spread. That same day, Texas Gov. Greg Abbott declared a state of disaster. citing the “imminent threat” posed by screwworms. while Texas officials said Canadian authorities were overreacting.

USDA officials have argued for urgency on the northward movement. The agency said the United States and Mexico are working together to eradicate NWS in Mexico. but added there has been “unacceptable northward advancement of NWS. and additional action must be taken to slow the northern progression of this deadly parasitic fly.”.

What makes New World screwworms so hard to stop is how quickly they can find a target. The CDC said the flies lay eggs on open wounds or other open parts of the body in living. warm-blooded animals. Even a wound as small as a tick bite can attract the flies. Eggs hatch into larvae. and those larvae burrow into the wound to feed on living flesh. which the CDC describes as different from most other maggots that feed on decomposing flesh.

After feeding, larvae fall to the ground and burrow into it, then later emerge as adult screwworm flies, according to the CDC.

The pain isn’t theoretical. Burrowing maggots in living creatures are highly painful, and officials have emphasized that early detection and proper treatment are critical.

Because the fly lays eggs in living wounds, the response has focused on prevention and large-scale sterile insect programs. Among the countermeasures the Department of Agriculture is using:

In Metapa, Mexico, the USDA invested $21 million to modernize an existing fruit fly facility. It is expected to open this summer and will produce 60 million to 100 million sterile NWS flies a week.

In Edinburg, Texas, a $750 million sterile fly production facility is under construction at Moore Air Base in South Texas. It will have a projected capacity of 300 million sterile flies a week and is expected to open in November 2027.

In Pacora, Panama, the USDA has been bringing in 100 million sterile flies a week from the COPEG facility in Panama. They are dispersed within and just north of affected areas in Mexico.

The federal government’s latest confirmation underscored that the problem is now being tracked inside U.S. borders. Secretary of Agriculture Brooke Rollins said that three additional cases of New World screwworm had been confirmed in the U.S., including two in Texas.

For people, officials say the danger is partly about recognition. The USDA says NWS infestations in humans are very painful and may be visible through maggots around or in an open wound or in the nose. eyes or mouth. Symptoms can include unexplained skin lesions (wounds or sores) that do not heal; skin wounds or sores that worsen over time; painful skin wounds or sores; bleeding from open sores; feeling larvae movement within a skin wound or sore or within the nose. mouth or eyes; seeing maggots around or in open sores; and a foul-smelling odor from the site of the infestation. Secondary bacterial infections can occur and may cause fever or chills.

In animals, symptoms include irritated behavior, head shaking, smell of decay, evidence of a fly strike, and the presence of fly maggots in wounds.

The CDC says maggots in a wound or a body part need to be removed by a medical professional, and people should not try to remove them themselves.

Until this cycle ends. the key question is how far the fly can move before the sterile program and detection efforts catch up. The sequence is stark: as cases surface across Texas and into New Mexico. officials are simultaneously scaling production and tightening responses on both sides of the border.

This story was updated to add new information.

New World screwworm Texas New Mexico USDA CDC sterile flies cattle beef prices Moore Air Base economic damage