Reporting a suspected New World Screwworm case isn’t just required by law – it’s the best way to protect your herd, your neighbors, and the American cattle industry. If you think you have a case, call your vet immediately.
Current Status in the United States
The first domestic case of New World Screwworm was confirmed on June 3, 2026. Several more cases have since been confirmed. Please check the dashboard below (which is maintained by USDA’s Animal and Plant Health Inspection Service) for the latest information.
Source: APHIS
Texas Animal Health Commission
- Map of infested zones and adjacent surveillance zones
- Hold order for Zavala and Uvalde counties
- Hold order for La Salle and Webb counties
New Mexico Livestock Board
Other Movement Orders & Guidance
The list below links to movement orders that states without cases have issued in response to the domestic detection of screwworm. We will keep it updated as efficiently as possible, but please always double check current guidelines and requirements on your state veterinarian, state livestock board, or state agriculture department’s website before moving cattle interstate.
Frequently Asked Questions
What is New World Screwworm?
New World Screwworm (NWS) infestations occur when the female fly lays eggs on an animal’s open wounds, orifices, or vulnerable areas like the umbilicus. The larvae (maggots) hatch and then invade the living tissue of the animal, feeding and burrowing deeper. Screwworm can impact any warm-blooded animal, and has occasionally been seen in birds. USDA successfully eradicated NWS from the United States in the 1960s using the sterile insect technique, which involves releasing sterile flies into the environment to gradually outcompete and reduce the natural population. The current outbreak advanced north through Central America in 2023, reaching Mexico in November 2024, and reaching the U.S. border in June 2026. NWS remains endemic in South America and parts of the Caribbean.
What are the Signs of Infestation?
Animals suffering from NWS infestation may exhibit the following signs:
- Bloody or light-colored drainage from a cut or wound.
- A cut or wound that rapidly enlarges for seemingly no reason.
- White or cream-colored runny substance (the eggs) in and around a wound.
- Presence of fly larvae (maggots) in wounds.
- Irritated behavior and signs of pain.
- Head shaking.
- Reduced appetite.
- Fever and other signs of secondary infection.
- Foul odor or smell of decay.
NWS larvae can infest something as obvious as a calf’s navel or a large wound, or as small as a branding, dehorning, or tagging site. Vigilant monitoring of your herd is essential. Keep in mind, NWS infestations are often hard to detect in the first 1-3 days. The larvae burrow below the skin; they usually are not seen crawling on the surface. As many as 200 parasitic worms can be found below the surface of what appears to be a small opening in the skin.
What Does the Screwworm Look Like?
Adult screwworm flies are about the size of a common housefly (or slightly larger). They have orange eyes, a metallic blue or green body, and three dark stripes along their backs. There is a pocket identification card linked above under “Resources.”What Should I Do If I Suspect a Case?
Contact your vet immediately if you see any signs of a potential screwworm infestation in an animal. Reporting is not only required by law; it’s the best way to protect the rest of your herd and your neighbors. If we don’t know where the problem is, we can’t fight it. Other next steps to take:
- You do NOT have to collect a sample and can wait for your vet to do it, but if you are going to collect a sample, there are some best practices to follow: collect maggots from the wound/orifice and place them in a sealed vial with rubbing alcohol. Wear gloves when you do this, and be very careful about any potential larvae dropping from the animal to the ground/soil. If possible, it’s best to place a tarp or plastic sheeting under the animal. If you don’t have the supplies or can’t collect a sample of larvae, just wait for your vet.
- Carefully inspect the other cattle in your herd and any dogs, horses, pets, or other animals on your property. Remember: signs of infestation can be hard to detect in the first 1-3 days. Even if a break in the skin looks small, inspect for signs of infestation.
Should I Be Worried About Beef?
No. New World Screwworm is an animal health problem, NOT a food safety problem.
Image courtesy of USDA.