The last recorded outbreak of the New World screwworm (NWS)—a parasitic fly that once devastated livestock, pets, and wildlife—in Oklahoma occurred in 1976.
As the NWS advances through Mexico, Oklahoma State University Extension specialists and educators are working proactively to ensure producers remain informed and prepared for a potential U.S. threat that many have only heard about.
The NWS could have major implications for animal agriculture, wildlife populations, and public health, said Dr. Rosslyn Biggs, OSU Extension veterinary medicine director of continuing education and beef cattle specialist, and assistant professor of veterinary clinical sciences.
“The time to develop a relationship with a veterinarian is not during an emergency,” Biggs said. “Every animal owner needs a veterinarian on their team—not just for screwworms, but to ensure animal health and welfare every day.”
Awareness is the first line of defense, Biggs added.
“We want to raise awareness among producers while ensuring consumers are informed and reassured,” she said. “This is not a food safety concern, but it is a real animal health threat. We need people actively watching for it.”
The New World screwworm is a zoonotic parasite that does not discriminate by species and can affect all mammals, including humans.
Through the use of sterile male flies, the NWS was eradicated from the United States, said Jonathan Cammack, OSU Extension livestock entomology and parasitology specialist and assistant professor of entomology and plant pathology.
“The primary control method for NWS is the sterile male insect technique,” Cammack said.
Male flies are raised in specialized facilities, sterilized using radiation, and released by airplane. Female NWS flies mate only once during their lifecycle, Biggs said. When they mate with sterile males, reproduction is halted.
However, Cammack noted that the closure of several sterilization facilities following eradication has complicated current control efforts as the parasite advances northward.
Staying Informed and Vigilant
Oklahoma State University continues to share up-to-date information on NWS and its potential impacts. Producers are encouraged to consult online resources or contact their local OSU Extension office for guidance.
Additional information, including tracking tools, is available through the U.S. Department of Agriculture.
The flight distance of the NWS fly varies with weather conditions, said Justin Talley, head of OSU’s entomology and plant pathology department. Locally, the fly typically travels about five kilometers, but it will continue moving until it finds a suitable host.
The fly lays eggs in wounds—sometimes as small as a tick bite—Biggs said. Once hatched, the larvae feed on live tissue.
The scientific name of the New World screwworm, Cochliomyia hominivorax, translates to “man eater” and reflects the insect’s destructive nature, Talley added.
An outbreak would pose a serious threat to Oklahoma’s agricultural economy, said Damona Doye, OSU Extension associate vice president and OSU Regents’ professor. The beef industry, the state’s largest agricultural sector, would be particularly vulnerable, with potential restrictions on livestock movement within Oklahoma and nationwide.
“We have many cattle producers who are unfamiliar with a problem that was once part of daily life,” Cammack said. “We are doing everything possible to educate county Extension educators so they can help producers address the threat.”
Early Detection is Critical
Through education, outreach, and surveillance, OSU Extension experts are taking a proactive approach to early detection.
Depending on the site of infection, infestations may be difficult to detect, Biggs said. Classic signs include maggots present in wounds—often arranged in a distinctive ridged pattern—along with head shaking, irritation, pain, depression, and a strong, foul odor.
If left untreated, NWS infestations can lead to death within 14 days. Newborn animals are especially vulnerable, as the parasite can infect the umbilicus. Untreated infections in newborns can result in 100% mortality.
County Extension educators across all 77 Oklahoma counties are receiving training and resources to support surveillance and response efforts. OSU Extension has also developed a dedicated webpage to keep educators and producers informed.
Collection kits have been distributed to support rapid response and sample submission if a suspected case occurs, said Bradley Secraw, Clemson University Extension consumer horticultural agent and former OSU Cleveland County agriculture and 4-H Extension educator.
“All 77 counties in Oklahoma have an Extension presence, and educators play a critical role in surveillance,” Biggs said. “They have been trained to recognize potential cases, collect samples and submit them properly.”
Samples can be submitted to the Plant Disease and Insect Diagnostic Laboratory (PDIDL) or the Oklahoma Animal Disease Diagnostic Laboratory (OADDL) on OSU’s Stillwater campus, both of which are equipped to identify NWS.
Extension specialists and county educators also host informational sessions for producers, helping establish local relationships and preparedness.
“The most important message for producers is not to panic, but to remain vigilant,” Cammack said. “Check animals regularly, monitor wounds and treat injuries promptly so they can heal quickly.”
As conditions continue to evolve, OSU Extension remains committed to protecting Oklahoma’s livestock, wildlife and companion animals by providing timely, accurate, and relevant information.
