New World screwworm cases climb to 52; first wild fly detected in U.S. trap
By TPR Staff
September 28, 2026 at 7:12 PM CDT
Last updated: Monday, Sept. 28, 2026
There have now been 52 confirmed New World screwworm animal cases in the United States since June, including 50 in Texas and two in New Mexico.
The latest case was confirmed Sept. 26 in goats in Crockett County, one of three animal cases currently considered active.
Officials also detected the first wild screwworm fly in a U.S. surveillance trap during the current spread. The fly was found in Brewster County on Sept. 25. The detection is tracked separately and is not included in the 52 animal cases.
The other active cases are a horse in Presidio County, Texas, confirmed Sept. 9, and a horse in Grant County, New Mexico, confirmed Sept. 17.
Federal officials have said the parasite’s northward spread has slowed, though the threat remains.
The USDA says it has released more than 1 billion sterile flies in Texas since February and is aiming to increase production to 500 million flies a week by next summer.
Agriculture Secretary Brooke Rollins has said officials are making progress but cautioned that the threat has not passed, pointing to Arizona and New Mexico as areas of concern.
“We’re not out of the woods yet,” Rollins said.
What is the New World screwworm?
Despite its name, the New World screwworm isn't a worm. It is the larval stage of the fly (Cochliomyia hominivorax), a parasite that feeds on the living tissue of warm-blooded animals.
Infestations begin when an adult female screwworm fly lays eggs in an open wound or natural body opening. Within hours, the eggs hatch and the larvae begin feeding on living tissue, unlike common maggots, which feed on dead or decaying tissue.
As the larvae burrow deeper into tissue, wounds become larger and often infected. Without treatment, infestations can be fatal.
(2560x2033, AR: 1.2592228234136744)
Which animals are at risk?
The screwworm primarily threatens livestock and wildlife, making it a major concern for Texas ranchers and animal health officials.
Animals at risk include:
Can people get New World screwworm?
Human infestations are rare. Most occur when untreated wounds are exposed in areas where the fly is circulating. The current outbreak primarily affects livestock, wildlife and pets.
Is it safe to eat beef and other meat?
According to the U.S. Department of Agriculture, New World screwworm is not considered a food safety threat. The parasite feeds on living tissue in open wounds — not meat intended for consumers — and animal health and inspection systems are designed to keep infested animals out of the food supply.
Symptoms to watch for
Early detection is critical. Animals infected with screwworm may show:
Why it matters in Texas
Texas has one of the largest livestock industries in the United States, along with extensive ranchland and abundant wildlife populations, particularly white-tailed deer. That combination makes the state especially vulnerable if screwworm becomes reestablished.
A widespread outbreak could lead to:
A screwworm fly stands on a leaf at a bio-factory as Mexico's government reconditioned a plant to become the new sterile screwworm fly facility, part of the country's effort to eradicate the flesh-eating parasite that threatens its livestock industry. (3000x2061, AR: 1.455604075691412)
How was it eradicated — and could it come back?
The United States eliminated screwworm using one of the most successful pest control programs in history: the sterile insect technique.
Scientists bred and released millions of sterile male flies. Because female screwworm flies typically mate only once, breeding with a sterile male produces no offspring, gradually collapsing the wild population.
That strategy eradicated screwworm from the United States and much of North America. However, the parasite remains present in parts of Central and South America, meaning the risk of reintroduction never fully disappears.
What should Texans do?
For most Texans, there is no reason to change their daily activities. The greatest risk remains to livestock, pets and wildlife.
Animal owners should:
If you suspect an infestation, contact your veterinarian immediately before transporting the animal.
Where to learn more
For the latest information and guidance, visit:
Have you seen a suspicious wound on livestock, wildlife or a pet? Do you have a question about New World screwworm?
Email the TPR newsroom at letters@tpr.org. Your questions, observations and experiences may help guide future reporting.
There have now been 52 confirmed New World screwworm animal cases in the United States since June, including 50 in Texas and two in New Mexico.
The latest case was confirmed Sept. 26 in goats in Crockett County, one of three animal cases currently considered active.
Officials also detected the first wild screwworm fly in a U.S. surveillance trap during the current spread. The fly was found in Brewster County on Sept. 25. The detection is tracked separately and is not included in the 52 animal cases.
The other active cases are a horse in Presidio County, Texas, confirmed Sept. 9, and a horse in Grant County, New Mexico, confirmed Sept. 17.
Federal officials have said the parasite’s northward spread has slowed, though the threat remains.
The USDA says it has released more than 1 billion sterile flies in Texas since February and is aiming to increase production to 500 million flies a week by next summer.
Agriculture Secretary Brooke Rollins has said officials are making progress but cautioned that the threat has not passed, pointing to Arizona and New Mexico as areas of concern.
“We’re not out of the woods yet,” Rollins said.
What is the New World screwworm?
Despite its name, the New World screwworm isn't a worm. It is the larval stage of the fly (Cochliomyia hominivorax), a parasite that feeds on the living tissue of warm-blooded animals.
Infestations begin when an adult female screwworm fly lays eggs in an open wound or natural body opening. Within hours, the eggs hatch and the larvae begin feeding on living tissue, unlike common maggots, which feed on dead or decaying tissue.
As the larvae burrow deeper into tissue, wounds become larger and often infected. Without treatment, infestations can be fatal.
(2560x2033, AR: 1.2592228234136744)
Which animals are at risk?
The screwworm primarily threatens livestock and wildlife, making it a major concern for Texas ranchers and animal health officials.
Animals at risk include:
- Cattle
- Horses
- Sheep and goats
- Pigs
- Deer and other wildlife
- Dogs and, less commonly, cats
Can people get New World screwworm?
Human infestations are rare. Most occur when untreated wounds are exposed in areas where the fly is circulating. The current outbreak primarily affects livestock, wildlife and pets.
Is it safe to eat beef and other meat?
According to the U.S. Department of Agriculture, New World screwworm is not considered a food safety threat. The parasite feeds on living tissue in open wounds — not meat intended for consumers — and animal health and inspection systems are designed to keep infested animals out of the food supply.
Symptoms to watch for
Early detection is critical. Animals infected with screwworm may show:
- Wounds that continue to worsen instead of heal
- Bloody, thick or foul-smelling drainage
- Swelling around an injury
- Visible larvae moving inside a wound
- Signs of pain, restlessness or unusual behavior
Why it matters in Texas
Texas has one of the largest livestock industries in the United States, along with extensive ranchland and abundant wildlife populations, particularly white-tailed deer. That combination makes the state especially vulnerable if screwworm becomes reestablished.
A widespread outbreak could lead to:
- Rapid spread through livestock and wildlife
- Increased veterinary and inspection costs
- Economic losses for ranchers and producers
- Potential impacts on livestock trade
- Threats to wildlife, particularly white-tailed deer
- Greater demand on veterinary and animal health services
A screwworm fly stands on a leaf at a bio-factory as Mexico's government reconditioned a plant to become the new sterile screwworm fly facility, part of the country's effort to eradicate the flesh-eating parasite that threatens its livestock industry. (3000x2061, AR: 1.455604075691412)
How was it eradicated — and could it come back?
The United States eliminated screwworm using one of the most successful pest control programs in history: the sterile insect technique.
Scientists bred and released millions of sterile male flies. Because female screwworm flies typically mate only once, breeding with a sterile male produces no offspring, gradually collapsing the wild population.
That strategy eradicated screwworm from the United States and much of North America. However, the parasite remains present in parts of Central and South America, meaning the risk of reintroduction never fully disappears.
What should Texans do?
For most Texans, there is no reason to change their daily activities. The greatest risk remains to livestock, pets and wildlife.
Animal owners should:
- Inspect wounds on pets and livestock regularly.
- Contact a veterinarian immediately if a wound worsens or contains larvae.
- Avoid transporting animals with suspicious wounds until they have been examined.
- Report suspected infestations to state animal health officials.
If you suspect an infestation, contact your veterinarian immediately before transporting the animal.
Where to learn more
For the latest information and guidance, visit:
- Texas Animal Health Commission: New World Screwworm resources
- USDA Screwworm.gov
- USDA Current Status dashboard and confirmed detections
- Your local veterinarian
- Your county extension office
Have you seen a suspicious wound on livestock, wildlife or a pet? Do you have a question about New World screwworm?
Email the TPR newsroom at letters@tpr.org. Your questions, observations and experiences may help guide future reporting.