Outbreak Of New World Screwworm Highlights Importance Of Insect Sterilization Technique Technology And Regulation

What Happened: The U.S. Centers for Disease Control and Prevention (CDC) recently issued a Health Advisory regarding outbreaks of New World Screwworm (NWS) outside the U.S. and the risk of spread into U.S. territory. The advisory underscores the continuing importance of the Insect Sterilization Technique (SIT), a tool historically central to NWS eradication, as well as the federal regulatory framework governing SIT-based technologies.

Who Is Impacted: Public health and agriculture industry stakeholders, including SIT developers and other pesticide product manufacturers in the U.S.

What Is the Insect Sterilization Technique (SIT)?

SIT is a biological pest control method involving the mass rearing and release of sterile insects, typically males, to suppress or eradicate a target population by mating with wild insects. When no viable offspring are produced, the population declines over time.

Traditional SIT programs rely on physical sterilization methods, such as irradiation, which the U.S. Department of Agriculture (USDA) typically regulates. By contrast, newer SIT-related approaches may involve biological, microbial, or genetic substances used on or in the released insects, which can trigger additional regulatory oversight by the U.S. Environmental Protection Agency (EPA) or the U.S. Food and Drug Administration (FDA).

NWS is a fly that can cause a parasitic infection known as myiasis by laying eggs in open wounds or other body cavities. NWS myiasis can be fatal to livestock, but also to humans and other warm-blooded animals. The current outbreak is in Central America and Mexico, including the Mexican state of Tamaulipas, which borders Texas. The U.S. federal government successfully employed SIT to eradicate NWS in the United States in the 1960s, although infestations occasionally reemerge, demonstrating the importance of understanding the regulatory framework of SIT-based technologies.

USDA-APHIS Regulatory Oversight

The USDA's Animal and Plant Health Inspection Service (APHIS) is the primary federal authority for many SIT programs. APHIS's role is rooted in its statutory authority to prevent the introduction, establishment, and spread of animal and plant pests such as NWS. Traditional irradiation-based SIT programs fall within APHIS's core authority.

Key Statutes:

• The Animal Health Protection Act, 7 U.S.C. §§ 8301–8317, authorizes USDA to prevent, detect, control, and eradicate livestock diseases and pests.
• The Plant Protection Act, 7 U.S.C. §§ 7701–7772 and 7781–7786, regulates the importation, exportation, and interstate movement of plants, plant products, certain biological control organisms, plant pests, and noxious weeds.

Under these statutes, APHIS generally:

• Leads SIT-based eradication and containment programs.
• Regulates the movement, importation, and release of sterilized insects.
• Coordinates with states and international partners.

EPA Regulatory Oversight

EPA may regulate SIT technologies under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) if the approach uses a substance that is intended to interfere with insect development or reproduction. While biological control agents are generally exempt from regulation under FIFRA (see 40 C.F.R. § 152.20(a)), EPA oversight applies to pesticidal substances (like bacteria or other microorganisms) used to interfere with an insect's reproductive cycle. These substances are considered pesticide products, and EPA must register them before they may be released into the environment via insect carriers (or otherwise distributed).

If FIFRA jurisdiction is triggered, EPA oversight may include:

• Registration or experimental use permits required for pesticides under FIFRA.
• Detailed labeling and conditions governing manufacture, distribution, and release.

New SIT technologies may require years of EPA review before they are registered as pesticide products. However, when certain criteria are met, EPA may exercise its authority under FIFRA Section 18 to issue limited emergency exemptions to address urgent public health and economic crises, including significant pest outbreaks.

FDA Regulatory Oversight

FDA, through its Center for Veterinary Medicine, has clarified its jurisdiction over certain SIT technologies in Guidance for Industry (GFI) No. 236 (updated August 2025). Like EPA, FDA oversight applies to certain products intended for use in or on insects. The Federal Food, Drug, and Cosmetic Act (FFDCA) charges FDA with regulating "new animal drugs," or drugs intended for use in animals other than man, which include articles "intended to affect the structure or any function of...other animals." FFDCA § 201(g)(1)(C); § 201(v). Recognizing that some substances used to control mosquito populations may meet both the definitions of "new animal drug" under FFDCA and "pesticide" under FIFRA, FDA's guidance clarifies that the FFDCA's definition excludes articles intended to function as pesticides (by preventing, destroying, repelling, or mitigating mosquitoes for population control purposes).

In practice, this means that the intended use of a particular substance often determines whether a particular SIT technology is subject to EPA jurisdiction under FIFRA or to FDA jurisdiction under the FFDCA. For example, FDA explains that its jurisdiction will generally apply to products intended to reduce the virus or other pathogen load within a mosquito, as well as products intended to prevent mosquito-borne disease in humans or animals. On the other hand, products intended to reduce mosquito populations by killing them or interfering with their reproduction or development will generally be subject to EPA regulation as pesticides under FIFRA.

If FFDCA jurisdiction is triggered, FDA oversight may include:

• Approval as a new animal drug and demonstration that the new drug is safe and effective before market distribution.
• Detailed labeling and quality standards governing manufacture, processing, packaging, and storage.

Recommendations

CDC's recent NWS advisory is a reminder that SIT remains a critical biosecurity tool. More than one federal agency may regulate SIT approaches, and jurisdiction often depends on whether a particular SIT approach involves a regulated substance and its intended use. As part of any SIT compliance strategy, impacted parties should carefully assess:

• Whether the technology relies solely on physical sterilization or uses a biological, microbial, or genetic substance.
• Whether the FIFRA exemption for biological control agents applies.
• How EPA and FDA responsibilities are allocated under GFI 236.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.