06/15/2026
NEW WORLD SCREWWORM: INFORMATION FOR LIVESTOCK & ANIMAL OWNERS
In early June, USDA APHIS announced the detection of New World Screwworm (NWS) in a calf in TX. This was the first detection of NWS in the United States since the 1960s. More cases have since been identified in calves, a dog and a goat.
What is New World Screwworm?
New World screwworm (NWS) is a type of parasitic fly that lays its eggs in open wounds or body openings (eyes, nose, mouth, etc.) of warm-blooded animals, including livestock, pets, wildlife, occasionally birds, and in rare cases, people.
What to Look For
Animal owners and veterinarians should always watch for signs of any illness in their animals.
Signs of NWS:
• Maggots or white egg masses in wounds or body openings, such as the nose or ears
• Foul odor or the smell of decay
• Signs of pain including irritated behavior, depression, not eating, and animals isolating themselves from other animals or people
• The flies are the size of a typical house fly with orange eyes and green iridescent bodies
• Wounds as small as a tick bite. TREAT FOR TICKS AND KEEP PETS ON FLEA/TICK PREVENTIVES YEAR ROUND.
Prevention
• Treat for ticks.
• Treat wounds promptly. Use fly spray and bandage when possible
• Closely monitor for wounds
• Check your vehicle for screwworm flies if you are in an NWS-infested area
What to Do if You Suspect NWS
Immediately report any suspicious wounds, maggots, or infestations. Animals infested with NWS, myiasis, or a secondary infection should be immediately treated by a veterinarian.