State Agencies Urge Vigilance Related to New World Screwworm

• July 20 2026

FOR IMMEDIATE RELEASE: July 20, 2026

CONTACT:
Dr. Tahnee Szymanski, Montana Department of Livestock 406-444-1587
Riley Meredith, Montana Department of Livestock 406-444-2788
Jennifer Ramsey, Montana Fish, Wildlife & Parks 406-577-7880

State Agencies Urge Vigilance Related to New World Screwworm

HELENA, Mont. – The Montana Department of Livestock (DOL) and Montana Fish, Wildlife & Parks (FWP) are urging the public to be vigilant and stay informed about New World Screwworm (NWS). NWS (Cochliomyia hominivorax) is a fly that lays eggs in wounds of any warm-blooded animal. The eggs hatch into larvae, commonly referred to as maggots, which feed on living tissue causing severe injury to and potential death of infested animals. This feeding behavior contrasts with the larvae of our local fly populations that will only feed on dead or decaying tissue. The NWS fly was eradicated from the United States in 1966, and its recent return has the potential to cause significant disruption and economic damage to the livestock industry.

As a pest of all warm-blooded animals, NWS can infest livestock, wildlife, poultry and other birds, dogs, cats, small mammals and humans. Livestock and animal owners should monitor animals for wounds and for signs of larvae infestation. Wounds with evidence of larval presence should be reported to your local veterinarian or DOL for follow-up. NWS is not a food safety issue and there is no need to stop or limit consumption of beef, pork, poultry, dairy, eggs or other livestock products.

Confirmed cases of NWS are currently localized to Texas and New Mexico. Operating with an abundance of caution, DOL has enacted an official order. This proactive measure increases entry requirements for all animals entering Montana from these affected states.

Montana’s additional import restrictions apply to all warm-blooded animals, including dogs and cats traveling with their owners. Restrictions and requirements for entry and/or reentry vary depending on whether the animal originated from or visited a restricted state or an infested zone within a restricted state. For a complete breakdown of Montana’s current restrictions, please refer to DOL’s official order found on the Department’s newsroom webpage at https://news.mt.gov/Department-of-Livestock/.

“We receive new information regarding NWS daily,” said Montana State Veterinarian Tahnee Szymanski. “As this is an evolving situation, we urge livestock producers, animal owners, hunters and wildlife enthusiasts to stay informed and remain vigilant. Information is available at the USDA website screwworm.gov and you can also contact DOL directly at 406-444-2976. If you are traveling, work with your local veterinarian to ensure compliance with any restrictions or requirements for states you may visit.”

Because NWS is a pest of all warm-blooded animals, care needs to be taken with wild animals as well.  Location information for any live or hunter harvested wild animal with maggots should be reported promptly to the local FWP office or the FWP Wildlife Health Program at 406-577-7880. Photos are helpful. Animals infested with NWS may show other symptoms such as head shaking, agitation, and foul odor. Do not handle or move suspect animals, because this may contribute to spread of the flies.

The mission of the Montana Department of Livestock is to control and eradicate animal diseases, prevent the transmission of animal diseases to humans, and to protect the livestock industry from theft and predatory animals. For more information visit liv.mt.gov.