New World Screwworm Update: What Producers Should Know in 2026
by Rosslyn Biggs, DVM, Oklahoma State University Extension
New World screwworm (NWS), Cochliomyia hominivorax , was eradicated from the continental United States decades ago through a coordinated effort that pushed the pest into Central America. For years, a biological barrier was maintained in Panama. The fly resurfaced in southern Mexico in late 2024. While the US remains free of an established NWS population, recent developments, including sterile fly release in Texas, expanded treatment options, and new infrastructure investments, highlight continued concern among animal health officials.
NWS larvae infest open wounds and feed on living tissue, causing pain, swelling, foul odor, and rapid tissue damage that can be fatal in less than two weeks if untreated. Female flies lay eggs in wounds, mucous membranes, and body openings. In cattle, risk is highest after branding, tagging, dehorning, castration, and at newborn navels, though even minor injuries can be targeted. Because females mate only once, control has relied on releasing sterile males to disrupt reproduction.
The sterile insect technique has historically been the hallmark of screwworm control and eradication. Sterile fly release has expanded into areas of northern Mexico and strategic locations up to 50 miles north into Texas. The goal is to create a preventive buffer zone inside the US, not just in Mexico, to intercept any flies that might move north. Movement controls have also been part of the response, and southern border ports between the US and Mexico remain closed to live ruminants.
Treatment options for control and prevention have also expanded, including emergency approval for macrocyclic lactone products, including Ivomec® (ivermectin) and Dectomax® (doramectin). ExZolt Cattle-CA1® (fluralaner) has also been conditionally approved as a topical solution for prevention and treatment. Use of these products in response protocols may occur under veterinary guidance and, in some cases, extra-label drug use provisions.
The opening of the sterile fly dispersal facility in Edinburg, Texas, in mid-February marked a major step forward. This facility will allow USDA to distribute millions of sterile male flies, strengthening the biological barrier designed to prevent the establishment of the pest. USDA also announced plans for a domestic sterile fly production facility nearby. The production plant represents an investment of roughly $750 million and is expected to eventually produce up to 300 million sterile flies per week, reducing reliance on international production and significantly expanding preparedness and response capacity.
In parallel, the USDA NWS Grand Challenge was announced to provide up to $100 million in funding to support research, surveillance, and improved control tools aimed at preventing NWS.
Australia’s 20-Year Agricultural Boom
Australian Department of Agriculture, Fisheries and Forestry
Australian agriculture is growing, adaptable, more productive, and well placed to take advantage of the transition to net zero, according to the latest Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) Snapshot of Australian Agriculture 2026 Insights paper.
Australian agriculture, fisheries, and forestry have grown by 45% in the last 20 years, with an increase in real terms from $69.3 billion in 2004–05 to $100.3 billion in 2024–25.
ABARES executive director Dr. Jared Greenville said the industry continued to demonstrate its strength, with the value of production reaching the third highest on record in 2024–25 in real terms. “The industry is looking really strong at the moment, and it’s in a good position to respond to any challenges, like climate variability, slower productivity, and global trade uncertainty,” Greenville said. “This has been the real marker of the agricultural sector’s success — its ability to change in response to consumer and market conditions, both in Australia and overseas. Not only has the total value of production increased, largely on the back of strong livestock and livestock product prices, but last financial year Australia’s agricultural, fisheries, and forestry exports were valued at $80.2 billion in real terms.”
China and the US are Australia’s biggest export markets, accounting for around 21% ($17 billion) and 12% ($9.3 billion) respectively of the value of agricultural and fisheries and forestry exports. “Outside of international trade, there are changes in the domestic space. As the net zero policy progresses, carbon sequestration will become a bigger part of land use,” Greenville said.
“While it will take up part of existing farming land, carbon sequestration is unlikely to impact heavily on a growing agricultural sector. Carbon sequestration also presents an opportunity for farmers to earn billions in revenue, provide on-farm diversification, and create a lower-cost transition pathway for the Australian economy,” Greenville added.
This follows an existing trajectory — over the three years to 2023–24, 92% of broadacre and dairy farms used at least one surveyed natural resource management practice. “There is also interest in expanding the use of these practices. We found 18% of broadacre and dairy farms are expecting to undertake at least one new on-farm activity to manage natural resources or reduce net emissions within the next two years,” Greenville shared.
The agricultural sector is also outperforming the rest of the Australian economy on productivity. “Cropping industry productivity growth was 1.6% per year on average between 1977–78 and 2023–24, while specialist sheep and beef industry productivity was 0.5% and 0.6%, respectively,” Greenville said.
