Brinda Dass is the deputy director of the nonprofit GeneConvene Global Collaborative.
Dass engaged in an email conversation with Progressive Cattle about the ongoing threat of New World screwworm and what biocontrol technologies might exist to help the U.S. livestock industry combat this pest.
What does the GeneConvene Global Collaborative do, and how is it involved in the agriculture and livestock industries?
DASS: The GeneConvene Global Collaborative supports informed decision-making about genetic biological control approaches for pests with public health implications, like mosquitoes that transmit malaria. We bring together researchers, policymakers and other stakeholders to answer important questions about the development and use of engineered mosquitoes, including those that contain gene drive elements, for the prevention of disease transmission, such as how to best evaluate safety and efficacy.
GeneConvene … understands that genetic biological control technologies have potential applications in the agricultural sector and monitors developments in this space. We sponsor the Gene Drive Research Forum, an international meeting that brings together representatives from health, agriculture and conservation to consider important questions about the potential uses of these technologies.
What factors have led to the northward spread of New World screwworm (NWS) over the past year after so many decades of successful eradication in Mexico and the U.S.?
DASS: The northward spread of NWS after decades of eradication reflects a convergence of biological, environmental and programmatic factors. Climate change and increasing temperatures have created favorable conditions for pupal survival and year-round reproduction, enabling rapid reinvasion from subtropical regions. NWS biology – especially females’ ability to lay multiple waves of eggs in wounds – allows populations to surge quickly even from small footholds. High-density livestock practices and insufficient inspection of animal trade further accelerate spread, with smuggling through the Darién Gap undermining surveillance. Wildlife, pets and humans act as reservoirs, compounding detection challenges. Sterile insect technique (SIT), historically successful, has been overwhelmed: Production of sterile flies cannot match population growth, forcing control lines northward. Budget constraints, political disputes and reduced funding have further weakened monitoring and response systems. Together, these dynamics explain how a long-maintained eradication barrier collapsed, allowing NWS to expand northward at alarming speed.
Is the sterile insect technique still effective?
DASS: Yes, the sterile insect technique remains a proven and effective method for controlling or eradicating pests like the New World screwworm. It was central to successful eradication campaigns in North America and continues to be the only tool capable of large-scale dissemination when international cooperation is strong. However, its effectiveness depends on several key factors. The fitness and competitiveness of sterile males are critical, as irradiation can reduce performance, requiring careful strain management and handling. Success also relies on sufficient scale and frequency of releases, complemented by robust surveillance. Timing is important; releases are most effective when wild populations are low, maximizing the sterile-to-wild male ratio. Ongoing improvements in strain development, rearing and sex separation technologies further strengthen outcomes. Modernization of irradiation methods, shifting from radioactive isotopes to X-ray or e-beam systems, can reduce logistical and security challenges, while maintaining sterility, provided dosimetry and quality control are rigorous. In short, SIT is highly effective when deployed strategically and at scale.
Your work includes a lot of research and application of genetic biocontrol technologies. What options exist along those lines for combating a pest like NWS?
DASS: Several genetic and genetic-adjacent biocontrol options are being explored for NWS, building on traditional SIT. Male-only sexing strains, including transgenic tetracycline-repressible (Tet-off) female-lethal systems, improve cost efficiency and field performance by ensuring that only sterile males are released. Recent constructs push lethality earlier in development, reducing rearing burden. Precision-guided SIT, which uses genetic sterility instead of radiation, is being tested in other pests but has not yet been applied to NWS. Gene drive strategies for population suppression are in preliminary development, while CRISPR-based editing (e.g., transformer disruption) has already been demonstrated in NWS enabling the creation of sexing strains, conditional lethals and marker lines. Genomic resources are rapidly improving: A chromosome-scale reference genome is available, and new USDA projects are enhancing assemblies for trait engineering and monitoring. Together, these advances highlight a growing toolkit that could complement or improve upon classical SIT for NWS control, though most approaches remain at research or early development stages.
How close to widespread adoption of some of these practices, like gene drives and genetically modified sexing strains, are we in the NWS fight?
DASS: Transgenic sexing strains (TSS) for NWS are relatively close to potential adoption in the U.S., with promising transgenic lines already developed that reduce rearing costs and improve release efficiency. Pilot trials could occur within two to five years, with phased integration alongside radiation-based SIT if regulatory reviews and risk assessments progress smoothly. These approaches may move more quickly through U.S. regulatory processes than gene drives, since they are self-limiting and resemble traditional SIT in persistence.
By contrast, gene drive systems remain in a very early research phase. Foundational tools like CRISPR-based disruptions, promoter mapping and split homing drive designs are under development, including USDA-funded work in surrogate species. However, regulatory uncertainty, ecological risks and public acceptance mean gene drives are at least five to 10 years from field use. Oversight will fall under the U.S. Coordinated Framework for biotechnology, which emphasizes safety, efficacy, environmental protection and stakeholder engagement. In the meantime, radiation SIT capacity expansion continues, with new USDA investments in sterile fly production and dispersal facilities.
What barriers exist to putting some of these emerging technologies into practice?
DASS: Barriers to deploying emerging genetic biocontrol tools for NWS are regulatory, cultural, economic and transboundary.
Regulatory systems were largely built around genetically modified (GM) plants, leaving no dedicated U.S. framework for GM insects or gene drives. Oversight would fall under the Coordinated Framework, potentially involving multiple agencies, which can slow reviews and create inconsistent requirements. Gene drives in particular would require tiered testing, robust biosafety and multinational agreements due to cross-border spread and use.
Cultural and social acceptance is another major hurdle. Public attitudes toward GM insects are polarized, with concerns about tampering with nature, irreversibility and ethics. Engagement of local communities, Indigenous groups and livestock producers is critical, as is transparency that builds trust.
Economic constraints include high costs of developing strains, rearing facilities and risk assessments, as well as uncertain benefit-cost ratios compared with scaling conventional SIT.
Finally, transboundary issues complicate adoption, since pests cross borders and differing regulations, trade implications and liability frameworks demand international coordination.
Together, these barriers underscore that technical readiness must be matched by regulatory clarity, stakeholder trust and sustainable investment.
How do you foresee the coming months going in the fight to keep screwworm out of the U.S. livestock industry? What advice do you have for producers and industry organizations?
DASS: In the near term, U.S. efforts to prevent NWS incursions will center on scaling up SIT, tightening import controls and intensifying surveillance. USDA is expanding domestic sterile fly production capacity and working with Mexico to add facilities, though construction and validation will take time. Border inspections, quarantines and heightened monitoring of livestock and wildlife are being reinforced with mounted patrols, detector dogs and coordinated binational efforts.
Outreach and education campaigns are equipping producers and veterinarians with training, identification materials and reporting channels. New tools – including novel attractants, trap-and-kill systems and genetically engineered strains – are under development, while the FDA has authorized emergency drug use for off-label use of existing treatment and prevention.
For producers, the best defense is vigilance: Practice good wound management, inspect animals regularly, strengthen biosecurity, coordinate closely with veterinarians and officials and report infections immediately. Industry groups should advocate for sustained funding, capacity building, active surveillance and reporting, and transparent communication to maintain public trust. Early detection and rapid reporting remain the most effective safeguards against NWS becoming established in U.S. herds.
For further information about biocontrol technologies for control of New World screwworm, visit the GeneConvene Global Collaborative website or contact us by email.
