On June 3, 2026, the USDA confirmed that New World Screwworm (NWS), a foreign parasitic pest, had entered the United States with a confirmed case in Texas. New World Screwworm (NWS) has the potential to cause serious damage to equine health and the agricultural economy.

Screwworm infestation is caused by fly larvae (maggots) that feed on living tissue of any animal and humans. The female flies lay the eggs in a wound. The eggs hatch in roughly 24 hours, and the maggots feed on live tissue for about seven days until they drop to the ground, pupate, and become flies. Screwworm infestations can be aggressive and, if left untreated, can kill an animal. Screwworm flies do not discriminate between hosts based on species. This outbreak is particularly concerning because it can impact any animal or human. Control of screwworm requires early identification and treatment of the host animal to prevent fly development. Once a case is confirmed, the USDA will release sterile male flies in the area to mate with wild female flies to produce infertile eggs, interrupting the breeding cycle.

For recent outbreak information, www.screwworm.gov

Evolving Situation

Once a case of screwworm is confirmed, state animal health veterinarians and the USDA draw a 20-kilometer or 12-mile radius around the case and consider this an “infested area.” Animals within this area will be allowed to move, but under restriction. We are still awaiting finalized response protocols from state and federal officials for movement of horses within an infested area. It is possible some states will restrict the gathering of animals in an infested area, so some states could effectively prohibit horse shows in infested areas. As the situation continues to evolve, US Equestrian remains in contact with state and federal animal health officials and will communicate updates as we receive them.

Hosting Events During This Outbreak

Competition management needs to be aware of and comply with applicable state and federal requirements. USEF requirements are based on state and federal animal health requirements. Unfortunately, we expect those state-by-state requirements could evolve as this outbreak goes on.

Competition management should:

• Consult the state veterinarian’s office to determine current restrictions, movement requirements, and any mandated response measures. Find your state veterinarian office contact information here.
• Maintain ongoing communication with USEF and both state and federal animal health officials as the situation progresses.

When you contact your state veterinarian’s office, here are some important questions you should ask:

• Can I hold a competition on this date at this venue?
• Do you have any requirements for an equine event in this location?
• I have horses coming from multiple states; do you have any requirements for animals entering my event from any state?
• Where can I find the latest information and guidance from your office for my event?

The state or federal animal health officials’ restrictions may be placed at the level of the infested premises, the infested area, infested county, or infested state. Restrictions officials have discussed could include: a temporary stop movement for 24-72 hours, inspection of all animals prior to movement off premises, examination and treatment of wounds prior to movement, or prohibition of movement of an animal with wounds.

A state free of NWS may place additional restrictions on horses coming from areas, counties, or states with confirmed NWS infestations.

If you’re holding multiple events over the course of the season, don’t assume that the guidance you received from the state at the last event is necessarily the same for your next one. We expect to see requirements shift with time.

Competitions Held in an Infested State

For competitions held in a state where screwworm has been confirmed (“an infested state”), competition management should anticipate the state will have additional requirements for horses coming to the event. Additionally, horses leaving the venue may have additional requirements placed on them by destination states, which usually includes inspection and certification provided to the destination state prior to leaving your event.
Competition management can support compliance with state requirements by:

• Communicating with state veterinarians in advance
• Coordinating with the competition veterinarian to prepare them for any inspection needs (incoming and outgoing horses)
• Making space and time available for required veterinary inspections
• Helping competitors understand that they are responsible for meeting the destination state’s requirements before departure (PENDING EDCC Link)

USEF Requirements for Competitions

To protect USEF competitions from the threat and impact of NWS, USEF is requiring competitions to implement specific mitigation protocols. If state protocols are more restrictive than USEF, state protocols must take precedence.

Legally, event management may not put restrictions in place that are stricter than USEF and the state without first contacting USEF at [email protected] for approval.

Note: Events which have other animals on the event grounds must contact USEF Equine Health and Biosecurity Veterinarian immediately upon knowledge of such case, as there could be additional risk for screwworm movement or infestation. USEF will provide additional requirements for these situations.

New World Screwworm Protocols for ALL USEF Licensed Competitions
Effective June 15, 2026

Until further regulatory protocols are implemented, USEF is implementing the following requirements and best practices for New World Screwworm. These protocols are based on federal and state guidance, in addition to what we know scientifically about screwworm. Please be aware that state, federal, and USEF guidance could change as the situation evolves. Visit usef.org/screwworm for the most updated information.

For the purposes of these protocols:

• An infested area is defined as the radius of 20 kilometers or 12 miles established by federal officials around a confirmed NWS case.
• An infested state is defined as a state with a USDA-declared confirmed case of New World Screwworm. Visit the USDA website for current outbreak information.
• Horse from an infested state is defined as a horse who has been physically present in an Infested State within the prior 14 days.
• Horse: For the purposes of this document, the term horse refers to any animal in the equine family, such as horse, pony, miniature horse, mule, donkey, or zebra.

REQUIREMENTS for all USEF Competitions:

• All competitors and competition management must comply with USEF screwworm protocols and state screwworm protocols and rules, inclusive of intrastate and interstate movement requirements. (Visit usef.org/screwworm for up-to-date information.)
• All competitions must require mandatory reporting and veterinary examination of wounds in horses from infested states.
• For competitions held in infested states, all horses with identified wounds must have those wounds treated topically with an FDA-authorized product for the treatment of screwworm. (You can find a list of authorized products for veterinary use, here.
  • Competition veterinarian must document treatment and email documentation to [email protected]
• All competitions must require immediate isolation of any horse determined by a veterinarian to be a suspected screwworm case.
• All competitions must immediately report any suspected screwworm lesion to their state veterinarian’s office AND to the USEF Equine Health and Biosecurity Veterinarian Dr. Katie Flynn ([email protected] or 859-225-6991).
  • Contact list for state veterinarian office: https://www.usaha.org/upload/Federal%20and%20State%20Health/STATE_ANIMAL_HEALTH_OFFICIALS_29.pdf)

REQUIREMENTS for the Management of Horses From USDA Identified Infested States

Inspection for Wounds

• Horses must be inspected for wounds prior to entering stabling areas. Any animal arriving in the trailer or any animal that has been in the trailer during travels (i.e. dog that is in the cab but was in the trailer), will be required to be inspected on arrival for wounds.
• Inspection must be done by an individual designed by the competition. The person designated to check animals for wounds does not need to be a veterinarian, however if a wound is found on an animal coming from an infested state, the wound will need to be examined by a veterinarian.
• For states where the state veterinarian requires an inspection by a veterinarian or authorized inspector, that inspection will meet the USEF requirements if it is conducted prior to the horse entering stabling.
• Horses who are not inspected are prohibited from entering the stables and must either go directly to isolation or leave premises until staff are available for inspection. USEF recommends the arrival of horses from an infested area be scheduled to ensure the proper inspector is available.
• Horses who are not stabling but who are haul-ins to a competition from an infested state will also need to be inspected for wounds.

Identification and Treatment of a Wound on Arrival

• Any identified wounds must immediately be inspected by the competition veterinarian for any sign of larvae. If an immediate examination is not possible, the horse must be placed in isolation.
• If any animal entering the show grounds from an infested state has a wound and also has documentation of wound treatment with an FDA-authorized product on their health certificate, a copy of such documentation shall be provided to competition management and USEF at [email protected].
• Animals shipping in from infested state with wounds who do not have documented evidence of wound treatment must be treated by the competition veterinarian with an FDA-authorized screwworm product prior to release for entry to stabling. Competition management must maintain documentation of treatment and provide a copy to [email protected].
• If larvae are found in a wound, it must be immediately reported to state veterinarian and USEF biosecurity veterinarian, and the horse must be immediately moved to isolation.
• If no larvae are found in a wound by the veterinary examination, the wound must be treated with an FDA-authorized screwworm topical product by the veterinarian, and the veterinarian shall maintain documentation of treatment. Remember, while larvae are visible to the naked eye, eggs are not.
• Any horse or animal with wounds must be inspected daily for 7 days to ensure no larvae appear in the wound. If the horse leaves the competition grounds before the 7 days is over, USEF ([email protected]) shall be notified of the horse details and the destination address of the horse for continued monitoring.
  • When a horse travels to another competition during this 7-day window, USEF will notify the competition management at subsequent venue of the need for continued monitoring.
• A horse from an infested area with a surgical incision created within the last 7 days will be prohibited entry if it enters without documented topical treatment with an FDA-authorized product for screwworm. Competition management must maintain documentation of treatment and provide a copy to [email protected].

Monitoring of Horses From Infested Area During the Event

• Whenever possible, horses from infested areas are to be stabled together in separate designated stables for monitoring purposes.
• Horses from infested areas should be visually observed for 7 days by designated licensed official or event staff daily for any evidence of NWS, new wounds, or evidence of larvae.
• Horses from infested areas with wounds at time of arrival should have the wound closely observed for 7 days by owners and by individual designated by management.
• Any newly identified wounds, larvae in wounds, or expansion of a previously identified wound should be immediately reported to competition veterinarian who will examine the horse.

Mitigation Efforts: What’s Being Done to Control This?

Previously, screwworm has been pushed out of the United States with the use of sterile flies. Officials in Mexico and the U.S. have been releasing sterile flies in recent months to try to disrupt the breeding cycle of the screwworm fly. This strategy takes some time to be effective and can be a challenge as the fly expands its range.
On a local level, both horse owners and facility owners can take steps to identify the presence of screwworm and discourage flies from being comfortable in their immediate vicinity.

Horse owners can:

• Inspect horses daily for evidence of wounds or larvae, paying attention even to small cuts as well as to vulnerable areas like healing surgical sites, umbilical areas, lips, nostrils, eyes, and genitals. The fly will lay eggs around moist areas with thin skin in addition to wounds.
• Report visual evidence of larvae and wounds that expand or don’t heal appropriately, as well as foul odors, discharge, irritation, stomping, or heightened irritation by the horse.
• Clean and protect wounds immediately and consult with veterinarians on the best products to use for wound care and dressing.
• Use veterinarian-directed fly control on horses, especially vulnerable areas of the body. Use masks, sheets, and other physical barriers to reduce fly access to horses.
• Remain vigilant about manure removal and standing water management.

Facility owners can:

• Establish a monitoring plan to discover wounds or larvae and educate staff on what to look for.
• Educate horse owners on the property about warning signs for infestation.
• Reduce fly breeding opportunities through prompt manure removal, proper disposal of waste feed and organic debris, and good drainage to reduce moist areas that attract flies.
• Use an integrated fly control program that may include sanitation, mechanical control, and appropriately labeled insecticides or premise sprays used according to label directions.
• Minimize standing water and maintain the property to reduce areas where flies congregate.
• Have a response plan for suspect cases that includes immediate veterinary contact, temporary isolation, movement restriction, and clear communication with staff.
• Monitor other susceptible animals on the premises as well, since NWS can affect livestock, pets, wildlife, and occasionally people.

Direct any questions regarding these protocols or New World Screwworm to Dr. Katie Flynn, USEF Equine Health and Biosecurity Veterinarian, 859-225-6991 or [email protected]

This is initial guidance and will be updated once the regulatory entities implement their protocols and procedures for movement of animals into and out of an infested area.