Officials confirmed new cases of New World screwworm in Texas wildlife and New Mexico livestock this week, marking the first detection in U.S. wildlife and prompting heightened surveillance.
Texas reported its first wildlife case on Oct. 21, when an elk infested with screwworm was harvested by a hunter on a game ranch in Pecos County. The Texas Parks and Wildlife Department and USDA are conducting additional wildlife surveillance in the area. Meanwhile, New Mexico confirmed a fifth case in a beef cow in Otero County on Oct. 19, following earlier detections in a horse and calf in Grant County on Oct. 15. State and federal officials have expanded fly trapping and surveillance around affected zones to monitor for further spread.
Immediate Response and Surveillance
The Texas Animal Health Commission will modify the state’s infested zone following the wildlife detection. In New Mexico, two infested zones are now in place, requiring inspections and treatment for animals moved within or out of the areas. State Veterinarian Samantha Holeck of the New Mexico Livestock Board stated, “We are working closely with our state and federal partners to investigate these cases, increase surveillance and monitor for additional infestations.”
New Mexico Secretary of Agriculture Jeff Witte noted, “This is a critical time as we move toward cooler weather. Cold daytime temperatures can slow screwworm activity, but the risk is not completely eliminated.” Grant County, home to an active cattle ranching community with approximately 25,000 head of cattle, remains a focal point for monitoring.
What Is New World Screwworm?
New World screwworm is a parasitic fly whose larvae feed on living tissue of warm-blooded animals, including livestock and, in rare cases, humans. The USDA emphasizes that while the pest does not affect food safety, it can impact meat production. The infestation begins when flies lay eggs in open wounds or body openings; once hatched, larvae burrow into tissue.
Typically found in South America and the Caribbean, the parasite has spread northward into Central America and Mexico in recent years. The first human case in the U.S. was confirmed in 2023, though officials reported no further transmission.
Detection and Reporting Protocols
Officials urge hunters, landowners, and outdoor enthusiasts to report suspicious signs, including:
- Visible maggots in wounds
- Foul-smelling injuries
- Weak or distressed animals
- Open or enlarging wounds
- Infestations around the nose, mouth, ears, eyes, or genital areas
The USDA’s Animal and Plant Health Inspection Service confirmed the presence of screwworm in a 3-week-old Texas calf in June. Surveillance efforts now include increased fly trapping and wildlife monitoring to identify additional cases and assess spread beyond the initial detections.