Highlights:
- UF/IFAS experts are monitoring the spread of the New World screwworm and providing resources for livestock managers, veterinarians, wildlife officials and community leaders, while emphasizing that no U.S. cases are currently reported.
- The USDA and CDC have issued updates on new cases in northern Mexico.
- UF/IFAS provides multiple public resources — including webinars, Ask IFAS publications, podcasts and expert contacts — to help communities understand screwworm risks, identify symptoms and access up-to-date management guidance.
Any suspected cases of New World screwworm in Florida should be immediately reported to FDACS.
The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is keeping a close eye on the status of New World screwworm, including recent spreading in northern Mexico, and experts are offering resources to community members, ranchers and other livestock managers, veterinarians and civic leaders of this emerging concern.
As of Jan. 26, there are no reports of New World screwworm in the U.S.
The New World screwworm is a type of fly, scientifically known as Cochliomyia hominivorax. Its maggots are the main concern because they feed on the living flesh of warm-blooded animals.
Unlike most maggots, which eat dead tissue and are helpful for decomposition, the New World screwworm maggot eats live, healthy tissue. Using an existing wound as a point of entry, they can burrow into a living animal with a wound and cause serious, sometimes deadly, damage to the animal, said Andrew Short, UF/IFAS chair of the Department of Entomology and Nematology.
The screwworm can infest livestock, pets, wildlife, sometimes birds, and — in rare cases — people.
All warm-blooded animals are at risk for a screwworm infection, especially if they have a recent, exposed wound or have just undergone surgery.
New World screwworms were in the U.S. since before the Civil War until they were eradicated in 1966.
In 2016, an infection spread in a population of Key deer in the Florida Keys. The infection continued until early 2017, when sterile fly treatment was successful in eliminating the screwworms from the environment. This is still the primary method of eradication used against the New World screwworm.
Press resources:
In light of the ongoing spread of the New World screwworm, UF/IFAS experts are available for the news media to discuss the latest developments in this issue. Please contact Meredith Bauer-Mitchell, UF/IFAS public relations specialist, at meredithbauer@ufl.edu to be connected with any of these sources.
- Edwin Burgess, UF/IFAS assistant professor of veterinary entomology, is available to discuss the New World screwworm as it relates to its risk to animals, as well as to discuss sterile fly facilities and the process of the sterile fly technique for controlling the New World screwworm.
- Todd Thrift, UF/IFAS associate professor of cow-calf management in the Department of Animal Sciences , is available to discuss the impact of this pest to the cattle industry, both internationally and domestically.
- Bridget Baker, UF/IFAS research assistant professor in the Department of Wildlife Ecology and Conservation , is available to discuss the impact of this pest on wildlife, as well as the 2016-2017 Florida Keys deer outbreak. Baker was involved in the effort to use sterile flies to eliminate that outbreak.
- Eva Buckner, assistant professor at the UF/IFAS Florida Medical Entomology Laboratory, is available to discuss the public health impact of pests.
Additional sources are available from UF Health and UF Veterinary Medicine.
Q&A: Please see this press release Q&A about the New World screwworm.
Florida resources:
- UF/IFAS New World screwworm webinar: UF/IFAS held an informational webinar about the pest and the current status as of the spread as of Sept. 17, 2025.
- UF/IFAS Ask IFAS: Ask IFAS has a peer-reviewed publication on the New World screwworm that explains a description of the pest, explanations of its life cycle, its impact on society as a pest and management and eradication of the fly.
- Cow Talks podcast: Cow Talks, a podcast produced by Marcelo Wallau, UF/IFAS forage Extension specialist, and Chris Prevatt, beef cattle and forage commodity director for the Alabama Farmers Federation have done several episodes that highlight the New World screwworm: one initial overview episode and one episode with the Florida Department of Agriculture & Consumer Services (FDACS).
- FDACS: FDACS has an informational website about the spread of the New World screwworm and what signs and symptoms to watch for in animals and people.
National resources:
- USDA main screwworm website: The federal government has launched a primary home page for information related to the New World screwworm. Hosted on the USDA’s Animal and Plant Health Inspection Services’ website, the shorthand for the website is “Screwworm.gov” and it provides resources for various groups, including livestock producers, veterinarians, pet owners and animal health officials.
July 9, 2025, update:
The USDA recently announced it will build an $8.5 million sterile fly dispersal facility in Texas focused on combatting the damaging and invasive New World screwworm.
The USDA reports that screwworms have been found in Mexico as far north as Oaxaca and Veracruz, about 700 miles from the U.S. border.
The eradication of New World screwworms is done through releasing sterilized flies into the environment, which mate with the local New World screwworm populations, stopping further reproduction. The population of New World screwworms then dies out. This technique was used to successfully combat a brief outbreak in the Florida Keys in 2016 and 2017.
To do this, the U.S. needs to release sterile flies – and a lot of them. The USDA’s proposed plans, according to a press release, also includes building a fly breeding facility that could produce about 300 million flies per week.
Jan. 22, 2026, update:
The U.S. Centers for Disease Control and Prevention issued a Health Alert Network Health Advisory on Jan. 20, 2026, in response to cases of the New World screwworm in northern Mexico, in the state of Tamaulipas, which boarders Texas. The alert provided clinical recommendations for what veterinarians and doctors should look for in the event that the New World screwworm crosses into the U.S.
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The mission of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS brings science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents.
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