New World Screwworm (Cochliomyia hominivorax) has re-entered the United States after advancing north through Mexico. USDA-APHIS confirmed the first U.S. case in a Texas calf on June 3, 2026, and additional cases have since been identified in Texas. Federal and state animal health officials have launched quarantine, surveillance and sterile-fly release programs to help contain the outbreak.

Why It Matters

NWS larvae infest living tissue, causing severe wound damage, secondary infections, weight loss and decreased production as well as potential death if left untreated. Any warm-blooded animal with an open wound can be affected, including beef and dairy cattle, horses, sheep, goats, pets, wildlife and occasionally humans. The economic impact could be significant due to treatment costs, production losses, animal welfare concerns and movement restrictions.

Symptoms to Watch For

• Infested animals may show:
• Irritated or restless behavior
• Head shaking
• Foul smell of decay
• Wounds that enlarge rapidly or fail to heal
• Maggots in wounds

Infestations are extremely painful and infected animals may stop eating or isolate themselves.

What Producers Should Do

• Inspect livestock regularly, especially after calving, dehorning, castration, branding, tagging or other procedures
• Promptly clean and treat wounds
• Watch closely for suspicious lesions or maggots
• Contact your veterinarian immediately if NWS is suspected
• Livestock marketers, transporters and sales representatives should remain vigilant when handling cattle from affected areas

If you suspect New World Screwworm, immediately report suspicious wounds, maggots or infestations to your veterinarian, your state animal health official and USDA officials.

Current FDA-Authorized Treatment & Prevention Options in Cattle

• Injectable doramectin (Dectomax) (Link: Search results for: 'Dectomax Injectable')
• Topical fluralaner (Exzolt Cattle-CA1)
• Injectable ivermectin (Ivomec) under Emergency Use Authorization (Link: Ivermectin Injection 1% [500 mL])
• Topical wound products including F10 Antiseptic Barrier Ointment, F10 Antiseptic Wound Spray and Negasunt Powder

Early detection and immediate veterinary involvement are critical to preventing the establishment and spread of New World Screwworm in the U.S. Please consult your veterinarian regarding appropriate treatment and prevention options to ensure all products are used safely, effectively and in compliance with label directions and current regulations.