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New World Screwworms Detected in a Cow in Nuevo León, Mexico

AUSTIN — On Sept. 21, Mexico’s National Service of Agro-Alimentary Health, Safety, and Quality (SENASICA) confirmed a positive detection of New World screwworm (NWS) in a cow in Sabinas Hidalgo, located in Nuevo León, Mexico, about 70 miles from the U.S.-Mexico border. Preliminary reports indicate the cow had been moved to a certified feedlot from a region in southern Mexico with known NWS cases.

The Texas Parks and Wildlife Department (TPWD) is working closely with the Texas Animal Health Commission (TAHC), U.S. Department of Agriculture (USDA) and additional partners to implement response plans and support NWS surveillance and reporting efforts along Texas’ southern border. Additionally, TPWD remains actively engaged with partners to provide education, training, preparedness initiatives, and contributing to a strategic and unified response to any potential spread.

To ensure a quick and effective response to NWS in Texas, those along the southern border or traveling from NWS-affected areas should closely monitor wildlife, livestock and pets for signs of NWS and immediately report potential cases to TPWD or TAHC.

General disease information, including what to look for, where to report cases, and how to prevent the spread of NWS can be found on the TPWD, TAHC and USDA websites.

What are New World screwworms:

New World screwworms (NWS) are parasitic flies (Cochliomyia hominivorax) that lay eggs in open wounds or mucous membranes such as the nostrils, eyes or mouths of live warm-blooded animals. These eggs hatch into a type of parasitic larvae (maggots) that only feeds on living tissue, while other species of fly larvae prefer dead or necrotic tissue. NWS larvae burrow or “screw” into living tissue with sharp mouth hooks, giving them a screw-like appearance. Infested wounds quickly become infected and, if left untreated, will kill the infested animals.

Clinical signs may include:

• Irritated or depressed behavior
• Loss of appetite
• Head shaking
• Smell of decaying flesh
• Evidence of fly strike
• Presence of fly larvae (maggots) in wounds
• Isolation from other animals or people

Reporting New World screwworm:

If you see LIVE animals with maggots, report to your local TPWD wildlife biologist. Early detection is key. Do not delay if you suspect an NWS infestation. Reporting is crucial to the implementation of management actions and eradication of NWS.

If you suspect wildlife with NWS infestations contact your local TPWD wildlife biologist.

Producers, veterinarians, diagnostic laboratories, or anyone else with suspicious livestock or domestic animals should direct reports to a TAHC Regional Office, or the 24-hour vet on-call line, 1-800-550-8242, within 24 hours of suspect or confirmed cases.

Prevention:

To avoid introduction of NWS, monitor pets and livestock closely for open wounds, and clean, treat, and cover any openings immediately. When traveling, especially in NWS-infested areas, ensure pets and vehicles are inspected for NWS flies and larvae before returning to the U.S.

Additional New World screwworm resources: