NAISMA joins the USDA’s Animal and Plant Health Inspection Service (APHIS) in raising awareness about a critical threat to animal health and agriculture in North America. On November 22, 2024, Mexico’s Chief Veterinary Officer confirmed a detection of New World screwworm (NWS) in Chiapas, a southern state near the border with Guatemala. This finding signals an alarming northward movement of this highly destructive pest, which has now reached Mexico after spreading through Central America.

What is New World Screwworm?

New World screwworm is the larval stage of the Cochliomyia hominivorax fly. Unlike typical maggots that feed on dead tissue, NWS larvae infest the living tissue of warm-blooded animals, including livestock, wildlife, and even humans. They enter through open wounds and feed on the host’s flesh, causing infections that can be fatal if untreated.

Why This Matters

The discovery of NWS in Mexico poses a severe threat to the U.S. livestock industry, wildlife, and public health. Left unchecked, NWS infestations could spread further north, jeopardizing ecosystems and causing devastating economic impacts. Infestations are notoriously difficult to detect early, as symptoms like enlarging wounds, discomfort, and visible larvae can appear only after significant damage has occurred.

Immediate Actions by APHIS

To protect U.S. animals and agriculture:

• Trade Restrictions: APHIS has imposed immediate restrictions on animal imports from or transiting Mexico until further notice.
• Enhanced Surveillance: APHIS is collaborating with Mexican and Central American partners to monitor and control the infestation while reestablishing a biological barrier in Panama.
• Sterile Fly Releases: APHIS is deploying sterile screwworm flies in affected regions to disrupt reproduction cycles and curb the spread.

How You Can Help

Producers along the southern U.S. border are urged to monitor their animals closely for signs of screwworm infestation, including:

• Wounds that enlarge or fail to heal
• Larvae or eggs around wounds (eggs are creamy white and deposited at wound edges)
• Behavioral changes indicating discomfort

If you suspect an infestation, immediately contact your veterinarian or local animal health authority. For pet owners, prompt veterinary care is critical. In the rare event humans suspect a lesion caused by NWS, they should seek immediate medical attention.

A Coordinated Response

The USDA has long partnered with Panama to maintain a biological barrier against NWS. However, recent challenges, such as increased livestock movement and changes in land use, have enabled the pest to bypass traditional containment areas. APHIS continues to collaborate with Central American nations to combat the spread through aerial fly releases and enhanced control measures.

Stay Informed

For more information on New World screwworm and the USDA’s response efforts, visit the APHIS website. Together, we can prevent this devastating pest from reaching U.S. soil and protect our agricultural and ecological systems.

NAISMA encourages its members and partners to remain vigilant and proactive in supporting measures to address this urgent threat. Stay connected for updates and guidance as this situation evolves.