06/05/2026
WHAT HORSE OWNERS NEED TO KNOW ABOUT NEW WORLD SCREWWORM
Recent reports of New World Screwworm (NWS) have raised concerns following confirmed detection in Zavala County, Texas. While the current risk in the US remains very low, understanding the facts can help horse owners stay informed and prepared.
What is New World Screwworm?
New World Screwworm is a fly whose larvae (maggots) feed on living tissue in warm-blooded animals. Horses, cattle, sheep, goats, wildlife, pets, and even humans can be affected.
Common Signs of Infection
• Maggots or white egg masses in wounds
• Infestations around the eyes, ears, nostrils, genitalia, or umbilicus of newborns
• Foul odor from a wound
• Pain, depression, decreased appetite, or isolation from herd mates
❌ Myth: All maggots found in a wound are New World Screwworm.
✅ Fact: Many fly species can cause maggot infestations. Laboratory identification is required to determine if New World Screwworm is present.
❌ Myth: New World Screwworm spreads directly from horse to horse.
✅ Fact: NWS is not contagious. Infestations occur when an adult fly lays eggs in a wound or body opening.
❌ Myth: One infected animal crossing the border will cause a nationwide outbreak.
✅ Fact: USDA maintains extensive surveillance, trapping programs, border inspections, and rapid response protocols designed to detect and contain any cases quickly.
What Horse Owners Can Do
✔ Inspect horses regularly for wounds
✔ Clean and treat wounds promptly
✔ Monitor healing closely
✔ Contact your veterinarian if you observe maggots, unusual wound appearance, or foul odor
✔ Practice good fly control throughout the year
At BE we encourage horse owners to remain vigilant but not alarmed. Early detection and prompt treatment are key! Resources : USDA Map of Current Outbreak: https://www.aphis.usda.gov/animals/animal-health/livestock-and-poultry-disease/current-status?page=1 and AAEP Alert to Equine Practitioners: New World Screwworm Enters the United States:https://aaep.org/wp-content/uploads/2026/06/Alert-to-Equine-Practitioners-FINAL.pdf