Minnesota experts urge awareness and vigilance
The U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed multiple cases of New World screwworm (NWS) in calves in Zavala and LaSalle counties in Texas and a dog in Lea County, New Mexico.
New World screwworm is a serious parasitic pest that affects livestock, pets, wildlife, and in rare cases, humans. The larvae invade and feed on the living tissue of warm-blooded animals.
The U.S. food supply remains safe, as screwworm infestations are detectable during inspection and do not affect meat products entering the food chain.
In response to these confirmations, the USDA has established zones with movement controls and surveillance, deployed response personnel, increased trapping and monitoring, and expanded wildlife surveillance and outreach. Millions of sterile flies have been released weekly along the U.S.–Mexico border since February.
Submit suspect maggots to appropriate authorities
State agencies and the University of Minnesota (UMN) have interdisciplinary teams monitoring the situation carefully. Key information for Minnesota livestock owners and veterinarians includes:
- While important, the situation is not currently urgent for Minnesota.
- New World screwworm would most likely be brought into Minnesota through livestock, horses, and companion animals traveling from Texas or other areas affected by NWS, as it does not overwinter in Minnesota’s climate.
- New World screwworm infections are treatable when identified early. Most importantly, the failure to recognize or treat early results in multiple generations of additional flies. Vigilance is essential.
- A recognized authority must identify suspect maggots. State animal health officials must be notified and samples submitted to the National Veterinary Services Laboratory.
- If suspect larvae or flies are received at the UMN Veterinary Diagnostic Laboratories in St. Paul or Willmar, they will be forwarded to the National Veterinary Services Laboratory within 24 hours for evaluation.
For more information, visit the Veterinary Diagnostic Laboratory website.
Monitor animals and your own health
The USDA, state agencies, and the University are encouraging vigilance.
- Animal owners should check for slow-healing or worsening wounds, signs of discomfort, and maggots in wounds or body openings (e.g., navel or vulva), especially in animals originating from or recently moved from NWS-affected areas.
- If infection is suspected, contact your veterinarian immediately.
- While rare, NWS can also infest people. People who travel to areas where NWS are present are also at risk, especially if they spend time around livestock or other animals, or have an open wound.
Contact your medical provider if you see or feel larvae in a wound or have a painful, non-healing wound following travel to an area where NWS is found.
The U.S. has successfully eliminated NWS in the past and is prepared to do so again through coordinated efforts. Ongoing surveillance and international response efforts have helped delay the reintroduction of the pest and strengthen preparedness.
State agencies and the UMN will continue to monitor developments closely and provide updates as new information becomes available. Stakeholders are encouraged to rely on trusted sources, including the USDA, university, and state animal health agencies.
See New World Screwworm in northern climates for more information on this insect.
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