California Ag Network

Tag: New World Screwworm

  • FDA Issues Emergency Use Authorization for Generic Drug to Prevent New World Screwworm in Cattle

    FDA’s 14th EUA against NWS

    The U.S. Food and Drug Administration issued an Emergency Use Authorization (EUA) for Bimectin (ivermectin) injection for the prevention of New World screwworm (NWS) infestations in cattle when administered within 24 hours of birth, at the time of castration or at the appearance of a wound Bimectin injection is not authorized for use in lactating dairy cows or in calves that will be processed for veal.

    Based on the available evidence, the FDA has concluded it is reasonable to believe that Bimectin injection may be effective for the prevention of Screwworm infections in certain cattle when used as authorized, and the known and potential benefits of the product outweigh its known and potential risks.

    “This authorization reflects the FDA’s commitment to expanding generic drug options against New World screwworm,” said Timothy Schell, Ph.D., director of the FDA’s Center for Veterinary Medicine. “By authorizing both generic and pioneer products, the Agency is ensuring producers aren’t dependent on a single manufacturer or product to protect their herds.”

    To maintain the continued safety of the food supply and avoid drug residues, it is critical that cattle producers carefully follow the 35-day slaughter withdrawal time and not administer this drug in lactating dairy cows and calves that will be processed for veal.

    Bimectin injection is a generic version of Ivomec, which was authorized in February 2026 for the prevention of NWS myiasis in cattle. The FDA previously approved Bimectin injection for the treatment and control of various parasites in cattle. This EUA is only for the Bimectin injection and does not authorize other dosage forms of Bimectin.

    Bimectin injection is available over the counter without a prescription. Cattle producers are responsible for using Bimectin injection in accordance with the product labeling and fact sheet.

    This EUA will be effective until it is revoked or the HHS Secretary terminates the declaration that the potential public health emergency presented by NWS justifies the emergency use authorization of animal drugs for NWS.

    Bimectin injection is sponsored by Bimeda Animal Health Ltd. based in Ireland.

  • Screwworm Strain Readied for Active Duty

    American scientific ingenuity in the form of sterile fly releases helped eliminate New World screwworm from the country in the 1960s. Now, ARS researchers are combining that ingenuity with next-generation tools to counter new resurgences of the pest threatening livestock and wildlife in New Mexico and Texas.

    “Releasing sterile screwworm flies is a proven, decades-old approach to eliminating populations of this pest and preventing the harm it inflicts—physically to livestock animals and wildlife and financially to the producers who raise livestock for our milk, meat, hide and other products,” said Kim Lohmeyer, Director of ARS’s Knipling-Bushland U.S. Livestock Insects Research Laboratory in Kerrville, TX. “Advances in genetics have now given us better tools to understand the screwworm’s population dynamics and leverage that knowledge for improved control methods, including sterile fly releases.”

    The latest example is NovoFly™, an all-male strain of screwworm developed by Lohmeyer’s team and university collaborators. With full regulatory approval of NovoFly™, critical resources can be redirected towards producing only males, essentially doubling the number available for SIT releases to eradicate established populations of the pest or isolate outbreaks of it.     

    Central to screwworm eradication is the Sterile Insect Technique (SIT). SIT is a biologically based approach to pest control that originated with the pioneering studies of ARS entomologists Edward B. Knipling and Raymond C. Bushland. That research began in the mid-1930s and continues today at the  Kerrville lab, which was posthumously named after these two entomologists.

    In January 2026, USDA Secretary Brooke Rollins and Deputy Secretary Stephen Vaden highlighted  SIT as part of a New World Screwworm Grand Challenge to counter recent U.S. incursions of the pest up through Central America.

    The SIT calls for releasing sterilized male flies near infestation areas where they can mate with wild female flies. The resulting eggs fail to hatch into flesh-eating larvae, which typically burrow into wounds or mucus-lined openings of livestock animals such as cattle—but also wildlife and, less often, pets and people.  Without larval offspring, the screwworm population eventually collapses, sparing animals further harm and reducing producers’ costs for insecticides, veterinary services, and medications.

    Despite SIT’s success in eradicating America’s indigenous screwworm population by 1966 (and eliminating subsequent resurgences of it), researchers saw room for improvement. “A sterile male can prevent a lot of wild females from reproducing, but a sterile female fly that mates only once doesn’t help with SIT,” explained Alex Arp, an ARS Research Geneticist who co-developed the all-male NovoFly™ strain.  While only sterile males are desirable, until now there has been no good way to separate them from females prior to SIT release, he added.

    Producing only male flies would increase production efficiency by doubling the number of male larvae that can be reared and male pupae that can be sterilized without major changes to production facilities. Without sterile females being released, sterile males have increased opportunities to mate with wild females, resulting in a more effective, efficient SIT program.

    Toward that goal, Arp and collaborators engineered Novofly™ with a genetic “switch” that kills female larvae during early rearing stages but doesn’t function in males. This allows for a doubling in the number of males that can be brought to maturity for release using the same amount of artificial diet and equipment.

    NovoFly™ is currently undergoing regulatory approval before the Environmental Protection Agency. Once approved, NovoFly™ will be mobilized for “active duty” at designated screwworm rearing facilities. USDA’s Animal and Plant Health Inspection Service coordinates SIT efforts in the U.S, Mexico, and Central America.

    “The research that went into creating NovoFly™ will provide the basis for the Grand Challenge project led by Max Scott of North Carolina State University together with Arp and many other collaborators,” Lohmeyer added—an effort that will set the stage for the next generation of this screwworm strain.

    To learn more about USDA’s whole-of-government approach to combatting NWS, visit “Stop Screwworm: Unified Government Response to Protect the United States”

  • NMPF Releases Statement on New World Screwworm

    The National Milk Producers Federation (NMPF) released a statement following the detection of New World screwworm in Texas last week. NMPF President and CEO Gregg Doud weighed in on the news stating:

    “The return of Wew World screwworm to the United States decades after its initial eradication is a disappointing milestone, but it’s also one for which dairy producers have been preparing for more than a year, in collaboration with USDA and across agriculture. It’s important to remember that this development has no effect on food safety, and that measures to combat both the screwworm and its spread are in place and time-tested. We appreciate the U.S. Department of Agriculture’s proactive efforts to prepare for this moment, and we stand ready to work with the department to address any ongoing challenges.

    Now that USDA has confirmed that screwworm is here, dairy farmers and all livestock producers pledge close collaboration with USDA, state and local officials, and producer organizations to mitigate any harmful effects and educate farmers on how to protect their herds. We have been creating resources to guide farmers in their responses, and we will keep our members well informed of any important screwworm developments.

    We also urge officials to follow scientific guidance in any decisions affecting animal movements and regulatory responses to avoid causing economic harm that could be greater than the screwworm itself. We also ask that adequate resources be provided to combat this problem, which causes suffering in animals and creates risk for producers.”

    Currently, no instances of New World screwworm have been reported in California.

  • New World Screwworm Detected in Texas

    The U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the detection of a New World screwworm (NWS) in a bovine in Zavala County, Texas. NWS is a serious pest that affects livestock, pets, wildlife, and less commonly, people and birds. NWS larvae (maggots) burrow into the flesh of living animals, causing serious damage to livestock and economic losses.

    The affected animal is a 3-week-old calf and larvae were identified in its umbilical area. To date, there have been no further detections.

    “All models showed New World Screwworm entering the country in 2025; however, thanks to the hard work across the entire Trump administration and our industry, state, and local partners, we were able to buy time for this moment. Protecting our livestock industry is a national security issue of the utmost importance, and USDA is wasting no time in taking action,” said Dudley Hoskins, Under Secretary for Marketing and Regulatory Programs. “USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico. The United States has defeated this pest before, and we will do it again.”

    USDA and Texas officials are taking immediate action to contain and eradicate NWS from the United States, following the strategies and actions outlined in the NWS Response Playbook (884.59 KB). This includes:

    • Forming a unified Incident Command Team with the Texas Animal Health Commission and deploying response personnel to the area;
    • Establishing a 20 km infested zone around the detection and implementing quarantines, movement controls and surveillance in this area;
    • Expediting targeted release of sterile NWS flies (423.58 KB) by immediately deploying ground release chambers in the area, in addition to the 4 million sterile flies per week already being released aerially in the area;
    • Increasing trapping for NWS flies along the border and just outside of the dispersal area;
    • Implementing NWS surveillance and management strategies in wildlife; and
    • Conducting targeted outreach in the local area.

    Additionally, USDA’s National Veterinary Stockpile stands ready to assist and will provide resources including treatments, equipment and logistics support the response as needed.

    USDA will continue to work with state departments of agriculture, animal health officials, industry and producers to mitigate economic impacts of restrictions as much as possible, including negotiating with our trading partners to regionalize any trade restrictions on live animals, limiting them to defined geographic areas.

    NWS maggots can infest livestock and other warm-blooded animals, including in rare cases people. They most often enter an animal through an open wound and feed on the animal’s living flesh.

    USDA urges residents in the area to check their pets and livestock for signs of NWS. Look for draining or enlarging wounds and signs of discomfort. Also look for screwworm larvae (maggots) and eggs in or around body openings, such as the nose, ears, and genitalia or the navel of newborn animals. If you suspect your animal is infected with screwworm, contact your state animal health official or USDA area veterinarian in charge immediately.

    While not common in people, if you notice a suspicious lesion on your body or suspect you may have contracted screwworm, seek immediate medical attention.

    The U.S. food supply is safe. Screwworms do not infest meat, fruits, vegetables, or other food sources. USDA’s Food Safety and Inspection Service (FSIS) ensures that the nation’s commercial supply of meat, poultry, and egg products is safe and properly labeled. Under the Federal Meat Inspection Act (FMIA), FSIS inspection personnel must inspect all eligible animal species unless they are exempt or covered by a state inspection program.

    Any evidence of screwworm infestation in an animal would be identified during these inspections, and any contaminated product from an affected animal would not be allowed to enter the food supply.

    For more than a year, USDA has led a unified response to NWS. As the lead coordinating agency, USDA has deployed advanced surveillance systems and supported robust cross-border response efforts in Mexico and Central America to combat the pest and push NWS away from the United States. These efforts have bought time for USDA to increase domestic preparedness efforts.

    Learn more about New World screwworm at Screwworm.gov. — Story contributed by the USDA Animal and Plant Health Inspection Service

  • USDA Completes Sterile Fly Dispersal Facility

    U.S. Secretary of Agriculture Brooke L. Rollins and Governor of Texas Greg Abbott visited Moore Air Base to  celebrate a significant achievement in the fight against New World Screwworm (NWS) with the completion of a U.S.-based sterile fly dispersal facility in Edinburg, Texas. This facility expands USDA’s ability to disperse sterile flies along the border and into the United States, if necessary.

    “The Trump Administration continues to bring the full force of the federal government to fight New World Screwworm,” said Secretary Brooke Rollins. “This sterile fly dispersal facility was a high priority project, and our team delivered it in record time. This new facility is a monumental achievement for our domestic preparedness efforts, but we are also diligently working to stop the spread of screwworm in Mexico, conduct extensive trapping and surveillance along the border, increase U.S. response capacity, and encourage innovative solutions. We will never stop fighting to protect American agriculture. USDA, through a whole-of-government approach, will continue to hold Mexico accountable to mitigating the spread of this dangerous pest.”

    “America is going to take care of ourselves, including dealing with the approach of screwworm as it gets closer to our border,” said Governor Abbott. “We put together the resources necessary for Texas to provide a Texas-size response to this. We thank Secretary Rollins and President Trump for stepping forward to provide the stop gap effort essential to protecting our ranchers and our wildlife.”

    Trump Administration NWS Response

    In June 2025, Secretary Rollins announced a sweeping five-pronged plan(PDF, 1005 KB) to enhance USDA’s already robust ability to detect, control, and eliminate NWS. As part of that announcement, she also shared plans to build this sterile NWS fly dispersal facility in South Texas. The completion of the facility further expands the network of dispersal facilities through Central America and Mexico and solidifies the increased preparedness offered by having a U.S.-based facility.

    On January 30, USDA announced a shift in its 100 million per week sterile fly dispersal efforts to reinforce coverage along the U.S.-Mexico border. While the sterile flies for this effort will initially be dispersed from the Tampico, Mexico facility, USDA is prepared to quickly and strategically shift operations to the new Texas facility should there be a change in the location or new concentration of NWS cases in northern Mexico.

    About Sterile Fly

    Sterile insect technique, when paired with surveillance, animal movement restrictions, and education and outreach, is a proven and effective tool for controlling and eradicating NWS. Female NWS flies only mate once in their lives, so if they mate with a sterile male, they lay unfertilized eggs that don’t hatch. Releasing sterile flies just outside of affected areas helps ensure flies traveling to new areas will only encounter sterile mates and will not be able to reproduce.

    Sterile insects are dispersed through aerial dispersal or ground release. Aerial operations are preferred because they allow for dispersal at a steady rate through a large area and also because sterile insects may be dispersed in areas that are unreachable from the ground. Ground release is used when there is a need to quickly deploy sterile insects outside of the dispersal facility range. Mass production and targeted dispersal of sterile flies remain critical components of an effective response.

    USDA currently produces sterile flies for dispersal at the COPEG facility in Panama. USDA is also investing $21 million to support Mexico’s renovation of an existing fruit fly facility in Metapa—which will double NWS production capacity once complete. With ongoing support from technical experts in USDA’s Animal and Plant Health Inspection Service (APHIS), Mexico anticipates this sterile fly production to begin as soon as summer 2026.

    To continue to expand USDA’s domestic response capacity, the Department is building a sterile fly production facility at Moore Air Base in Edinburg, Texas, with a targeted maximum capacity of 300 million sterile flies per week. USDA expects to break ground on that facility later this spring. With existing and planned production facilities fully operational, USDA will have up to 500 million sterile files per week in its arsenal to fight this pest all the way back to the Darién Gap. The international network of facilities will produce 100 million sterile flies per week at COPEG in Panama, 100 million at Metapa in Mexico, and 300 million at Moore Air Base.

    What You Can Do

    Even though there have been no detections of NWS inside the U.S. and the northernmost active case of NWS is still about 200 miles away from the border, USDA is asking Americans to continue to remain vigilant by checking their livestock and pets for signs of NWS. Look for draining or enlarging wounds and signs of discomfort. Also look for NWS larvae (maggots) and eggs in or around body openings, such as the nose, ears, and genitalia or the navel of newborn animals. If you suspect your animal is infested with NWS, immediately report it to your state animal health official or USDA area veterinarian in charge.

    NWS maggots can infest livestock and other warm-blooded animals, including people. They most often enter an animal through an open wound and feed on the animal’s living flesh. While not common in people, if you notice a suspicious lesion on your body or suspect you may have contracted NWS, seek immediate medical attention. — USDA

  • USDA Shifts Fly Dispersal Efforts to U.S. Border

    The United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) is announcing a shift in its 100 million per week sterile fly dispersal efforts to stop the northern spread of New World screwworm (NWS). USDA will reallocate aircraft and sterile insects to reinforce coverage along the U.S.-Mexico border. The new dispersal area, or polygon, will include operations about 50 miles into Texas, along the U.S. border with the state of Tamaulipas, Mexico. Mass production and targeted dispersal of sterile insects are critical components of an effective strategy to fight NWS. Other tools including import protocols and surveillance continue to support these robust efforts to keep NWS out of the United States.

    “At Secretary Rollins’ direction, our highest priority is protecting the United States from screwworm,” said Dudley Hoskins, Under Secretary of Marketing and Regulatory Programs for USDA. “The northernmost active case of NWS in Mexico is still about 200 miles away from the border, but we’ve seen cases continue to spread in Tamaulipas and further south in Mexico, so we are proactively shifting our polygon as we make every effort to prevent NWS from reaching our border.”

    Sterile Fly Dispersal

    Sterile insect technique, when paired with surveillance, movement restrictions, and education and outreach, is an effective tool for controlling and eradicating New World screwworm. Female New World screwworm flies only mate once in their lives, so if they mate with a sterile male, they lay unfertilized eggs that don’t hatch. Releasing sterile flies just outside of affected areas helps ensure flies traveling to new areas will only encounter sterile mates and will not be able to reproduce. In this instance, USDA will release sterile flies north of the current active NWS cases in Mexico in a proactive effort to create a sterile reproduction buffer zone if the fly moves north from Mexico.

    Because it is important to continue ongoing surveillance efforts while releasing sterile insects, it is possible that sterile NWS flies could be caught and/or reported within Texas. To ensure officials can tell the difference between sterile and wild NWS flies, USDA will dye the sterile pupae, and the dye will transfer to the sterile flies when they hatch. The fluorescent dye will glow under UV light and may also be visible to the naked eye. If a sterile fly is captured in a trap, this dye will allow animal health officials to quickly rule the fly out as a threat.

    USDA will continue to deploy its intensive NWS response efforts including implementing import protocols, ongoing surveillance and trapping efforts along the border, investing in NWS innovation, and supporting robust response activities in Mexico and Central America.

    Import Requirements and Protocols

    Sterile insects are an important tool, but USDA’s import requirements and protocols add another line of defense for NWS and other foreign animal diseases that threaten U.S. livestock. Earlier this week, the importance of those protocols was highlighted when a horse from Argentina was presented for routine importation at an equine import quarantine facility in Florida. Upon examination, APHIS identified an open wound with larvae on the animal and promptly collected and shipped samples to the National Veterinary Services Laboratories (NVSL) in Iowa. The horse was immediately treated with medication to kill any larvae in accordance with standard, long-standing import protocols. This morning, NVSL confirmed that the larvae were New World screwworm larvae. Accordingly, the animal will remain in quarantine until it has been reexamined and determined to be free of NWS.

    This is an example of these long-standing import protocols working as designed. While this situation does not appear to be associated with the NWS outbreak in Mexico that USDA is currently fighting, it underscores the need for vigilance in all of USDA’s coordinated efforts to fight NWS.

    Surveillance, Monitoring, and Reporting

    USDA continues to lead intensive surveillance and monitoring systems along the U.S. border. Teams continue to check 121 NWS-specific traps across high-risk areas of border states and leverage thousands of fruit fly/insect traps aligned all along the Southern border. To date, more than 42,000 flies from traps in all locations have been submitted to APHIS NVSL for identification, with no NWS detections to date. APHIS Wildlife Services is also leading a coordinated effort to inspect wildlife for signs of NWS infestation. To date, they’ve inspected more than 9,300 wild animals across 39 different species and 131 U.S. counties and found no signs of NWS infestations.

    Even though there has been no detection of NWS inside the U.S. and the northernmost active case of NWS is still about 200 miles away from the border, USDA is asking U.S. animal owners to continue to remain vigilant by checking their pets and livestock for signs of NWS and immediately reporting anything suspicious to their state animal health officials or USDA area veterinarian in charge. Signs of NWS infestation include draining or enlarging wounds and signs of discomfort. Also look for screwworm larvae (maggots) and eggs in or around body openings, such as the nose, ears, and genitalia or the navel of newborn animals.

    Adult screwworm flies are about the size of a common housefly or slightly larger, with a metallic green or blue body, orange eyes, and three dark stripes down its back. NWS maggots can infest livestock and other warm-blooded animals, including people. They most often enter an animal through an open wound and feed on the animal’s living flesh.

    While NWS is not common in people, if you notice a suspicious lesion on your body or suspect you may have contracted screwworm, seek immediate medical attention.

    For more information on NWS and USDA’s efforts, visit Screwworm.gov. — USDA Animal and Plant Health Inspection Service

  • USDA Announces New World Screwworm Grand Challenge

    Today, U.S. Secretary of Agriculture Brooke L. Rollins announced the launch of the New World Screwworm (NWS) Grand Challenge. This funding opportunity marks a pivotal step in USDA’s comprehensive strategy to combat NWS and prevent its northward spread.

    “This is a strategic investment in America’s farmers and ranchers and is an important action to ensure the safety and future success of our food supply, which is essential to our national security,” said Secretary Brooke Rollins. “These are the kinds of innovations that will help us stay ahead of this pest and protect our food supply and our economy, protecting the way of life of our ranchers and go towards rebuilding our cattle herd to lower consumer prices on grocery store shelves. We know we have tried-and-true tools and methods to defeat this pest, but we must constantly look for new and better methods and innovate our way to success. Together, through science, innovation, and collaboration, we can ensure we’re utilizing the latest tools and technology to combat NWS in Mexico and Central America and keep it out of the United States.”

    As part of the Grand Challenge, USDA’s Animal and Plant Health Inspection Service (APHIS) will make up to $100 million available to support innovative projects that enhance sterile NWS fly production, strengthen preparedness and response strategies, and safeguard U.S. agriculture, animal health, and trade.

    Priority Areas for Funding

    APHIS invites proposals that support one or more of the following objectives:

    • Enhance sterile NWS fly production
    • Develop novel NWS traps and lures
    • Develop and increase understanding of NWS therapeutics/treatments (i.e. products that could treat, prevent, or control NWS) for animals
    • Develop other tools to bolster preparedness or response to NWS

    The notice of funding opportunity, including application instructions, eligibility, and program requirements, is available on the NWS Grand Challenge webpage. Applicants can also find information on the ezFedGrants website or Grants.gov by searching USDA-APHIS-10025-OA000000-26-0001.

    Eligible applicants are invited to submit proposals that align with and support these priorities by the deadline on February 23, 2026 at 11:59 PM ET.

    Entities interested in submitting a proposal should ensure they are registered with the U.S. Government System for Award Management (SAM). Learn more about the basics of the funding process and how to get ready to apply.

    For more information about NWS, visit screwworm.gov. Sign up here to have the latest NWS updates delivered to your inbox.