The US confirmed three new cases of New World screwworm, or screwworm fly, this Monday (8), bringing the total to five since the first domestic infestation in six decades, detected in a calf in the US state of Texas last week.
A , including livestock, pets, wild animals and, in rare cases, people. The larvae penetrate the living tissue of animals, causing serious injuries, animal suffering and significant economic losses.
The USDA’s Animal and Plant Health Inspection Service (APHIS) confirmed two new cases in Texas, including infestations in a calf in La Salle County and a goat in Gillespie County.
APHIS clarified that a fifth case previously reported on Monday, in a dog in Andrews County, would be reclassified as the first case detected in New Mexico.
The veterinarian who reported the case is located in Texas, the agency said, but the dog resides in a home in Lea County, New Mexico, which borders the state.
Agriculture Secretary Brooke Rollins said at a news conference Monday in Kerrville, Texas, that the agency will soon begin announcing recipients of funding from a $100 million fund for pest technologies announced last year.
Rollins spoke alongside Texas Governor Greg Abbott in front of signs reading “War on Screwworms.”
Reuters reported last year that hundreds of veterinarians, support staff and laboratory workers in the USDA’s animal health sector left the agency following pressure from the Trump administration for layoffs, resulting in fewer specialists to respond to disease outbreaks in animals and raising concerns about the level of preparedness.
Rollins stated that these layoffs were not affecting the parasite response.
The second case of the parasite was confirmed in Texas by the USDA last Friday (5), emerging just a few miles from where the first detection in the US in decades was reported last week.
Local Texas residents and ranchers remain divided over whether to trust the USDA’s response, with some farmers saying it is too slow or not comprehensive enough, while those who experienced the latest outbreak said the news has further eroded their trust in the agency, leading them to seek their own solutions.
Deadly parasite
Fly is not a contagious disease that spreads from animal to animal. Instead, adult females lay their eggs in fresh wounds of warm-blooded animals.
The larvae feed on the host and can damage vital organs or cause serious bacterial infections. Cases can be severe and even lead to the death of the host animal.
The parasite also poses a threat to wildlife and pets. Veterinarians in Texas, Arizona and New Mexico have been told to be on the lookout for new infections.
On Wednesday, the U.S. Secretary of Agriculture warned pet owners to be alert for signs of discomfort, open wounds or larvae or eggs near holes in the body.
Cases in humans are rare but can be fatal. The last person in the U.S. to contract the blowfly infection was a case in Maryland in August of a person who had traveled outside the country. She recovered completely.
Low threat to humans
Brooke Rollins said Tuesday that the current threat to human health is extremely low and that the blowfly does not pose a risk to food security, but that “there is no doubt that this is a very, very serious threat to our livestock.”
People most at risk of contracting New World screwworm are those who work with livestock or other warm-blooded animals in areas where flies are present and those who spend a lot of time outdoors, especially if they sleep outdoors.
People with health problems that cause bleeding or open wounds may also be vulnerable to infection.
Any open wound, even a small break in the skin like a scratch or insect bite, can attract these flies, according to the U.S. Centers for Disease Control and Prevention.
In August, the U.S. Department of Health and Human Services began allowing emergency use of medications to treat or prevent infestations in animals. A shipment of that treatment is on its way to South Texas, Rollins said Wednesday.
The USDA says it has created new monitoring, testing and quarantine protocols in response to the outbreak spreading across Central and South America.
In May 2025, the agency suspended the import of live animals through U.S. ports of entry along the southern border.
The department has stationed sniffer dogs on the border with Mexico capable of detecting the New World screwworm and sent teams to the neighboring country and Panama to help increase the production of sterile flies.
The US has also committed $750 million to build a facility in Texas that will produce hundreds of millions of sterile flies per week. This facility is expected to open next year.
(With input from Jen Christensen of CNN)
