New World Screwworm
New World Screwworm
New World screwworm (NWS) is a parasitic fly detected in Texas and New Mexico in June 2026. Currently, there are no detections of New World screwworm in Connecticut.
Current Status
No confirmed cases in Connecticut.
CT NWS Animal Movement and Restricted Entry Order
What Is the New World Screwworm?
The New World Screwworm (Cochliomyia hominivorax) is a parasitic fly whose larvae feed on the living tissue of warm‑blooded animals. Unlike common maggots that consume dead tissue, screwworm larvae invade healthy flesh, causing rapidly worsening wounds and, if untreated, death.
The name screwworm refers to the maggots’ feeding behavior as they burrow (screw) into the wound, causing extensive damage by tearing at the hosts’ tissue with sharp mouth hooks.
NWS poses a serious threat to livestock, pets, wildlife, and in rare cases, people. Untreated cases can kill an animal in 10-14 days. Although human cases are rare, deaths have been reported.
What to Look For
NWS infestations can be difficult to detect at first. Early detection is critical. Report mammals and birds with 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.
Any suspicious wound on a pet, livestock animal, or wildlife should be taken seriously.
Adult screwworm flies are about the size of a common housefly or slightly larger and have orange eyes, a metallic blue or green body, and three dark stripes along their back.
How to Protect Animals from New World Screwworm
- Watch for NWS signs in pets and livestock, particularly unhealing wounds, odors, or changes in behavior, especially if animals have travelled to or from areas known to have active NWS infestations.
Make sure pets traveling internationally are inspected for screwworm. - Handle livestock carefully and inspect pens and equipment for sharp objects that can cause wounds.
- Treat the umbilical cords of newborn animals and all wounds immediately with an approved insecticide.
- Protect pets and livestock from other wound-causing parasites such as ticks.
What to Do if You Suspect New World Screwworm
NWS is a nationally notifiable foreign animal disease. Suspected cases in any warm-blooded animal (livestock, pets, wildlife, or humans) must be reported immediately.
Please contact:
- Connecticut State Veterinarian’s Office: 860-713-2505 office or 860-713-2725 or ctstate.vet@ct.gov
- USDA APHIS Veterinary Services: 866-536-7593
- If human involvement is suspected, notify the Connecticut Department of Public Health: 860-509-7994
- If you see wildlife with signs of screwworm, contact the APHIS Wildlife Services office in your state by calling 866-4USDA-WS (866-487-3297).
If you see maggots in a wound or an injury that is unexpectedly worsening call your veterinarian immediately.
Early reporting is essential to protect both animal health and the region’s agriculture.
Treatment
If NWS were detected, treatment must be performed by a licensed veterinarian and may include:
• Safe removal of larvae
• Wound cleaning and antibiotics
• Medications to prevent reinfestation
• Supportive care depending on the severity
Timely veterinary treatment is highly effective when the infestation is caught early.
- Approval & Conditional Approval of Animal Drugs for NWS
- Emergency Use Authorization of Animal Drugs for NWS
- Extralabel Use of Animal Drugs for NWS
- FDA-Conditionally Approved and Authorized Animal Drug Options for New World Screwworm
Is the Food Supply Safe?
Yes. NWS is not a food safety issue, and the U.S. food supply remains safe. All animal meat and poultry must meet food safety standards, and no contaminated meat or poultry products can be sold. Increased monitoring and control measures are being implemented by authorities and public health officials are actively managing the situation to prevent spread.
Resources and More Information
USDA: NWS Response Playbook
USDA: New World Screwworm Prevention for Animals
USDA: Confirmed Detections of New World Screwworm | APHIS
USDA: New World Screwworm: What you need to know before traveling internationally with a pet
USDA: New World screwworm: Be Aware and Prepare (PDF)
FDA: New World screwworm: Information for Veterinarians (FDA)
CDC: New World Screwworm and human health
New World screwworm webinar for veterinarians and animal health regulatory officials
The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) hosted an informational webinar for veterinarians and animal health regulatory officials about the New World screwworm. This webinar describes the pest’s life cycle and the damage it causes; explains how to detect and report suspected cases; and reviews USDA’s response plans, should there be a detection in the United States.