New World screwworm is an urgent wound and animal-health reporting problem, not a routine home-care problem. Horse owners should inspect wounds and vulnerable body areas closely, stop unnecessary movement when an infestation is suspected, and contact a veterinarian immediately if they see moving larvae, a rapidly enlarging wound, foul odor, unusual drainage, marked pain, or concentrated fly activity.

By Jon Conklin | Published July 20, 2026 | Reviewed July 28, 2026

Current United States situation

USDA's current-status page directs owners to a live dashboard for confirmed U.S. animal and wild-fly detections and warns that an individual case becoming inactive does not automatically end an area's infested-zone restrictions.

All southern ports of entry remain closed to livestock trade under the current federal status page. USDA has announced a conditional phased reopening beginning with cattle trade at Douglas, Arizona, on August 24, 2026. Later consideration of Santa Teresa and Columbus, New Mexico, may include cattle, bison, and horses, depending on risk and response milestones.

States may impose additional requirements. Florida, for example, issued temporary July 2026 restrictions for warm-blooded animals arriving from designated infested and high-risk areas. Riders should confirm the exact rules for their origin, route, destination, and travel date.

Where to inspect a horse

Use good light and look at the whole wound, not just the surface. Many fly species look alike, so owners do not need to identify the adult fly. The practical job is to find suspicious wounds or larvae early and report them.

Signs that require immediate action

These signs are not proof that New World screwworm is present, but they are enough to stop guessing and call a veterinarian.

What to do when screwworm is suspected

1. Stop unnecessary movement

Do not haul the horse to a show, clinic, boarding barn, or another property unless a veterinarian or animal-health official directs the movement. Keep the horse in a practical low-fly area and limit shared equipment while instructions are being arranged.

2. Call a veterinarian immediately

Outside Texas, USDA directs livestock owners to contact a veterinarian for evaluation. In Texas, owners should follow the current Texas Animal Health Commission reporting route. Veterinarians and animal-health professionals coordinate reporting with state and federal officials.

3. Protect the evidence

Wear gloves. Do not discard larvae, flood the wound with harsh chemicals, or aggressively clean away material that officials may need for identification before receiving instructions. Photograph the wound only when it can be done without delaying care.

4. Separate supplies

Use dedicated gloves, buckets, towels, bandage supplies, and grooming tools for the affected horse until the situation is evaluated. New World screwworm is not managed like a routine contagious respiratory disease, but dedicated equipment reduces accidental wound contamination and keeps the response organized.

5. Monitor the rest of the barn

Inspect every horse for fresh wounds and vulnerable sites. Record findings, recent travel, procedures, new arrivals, and the dates wounds were first noticed.

Emergency-authorized drugs: what the FDA guidance actually says

FDA has issued Emergency Use Authorizations for two drugs to help prevent New World screwworm in certain susceptible horses. Neither authorization is a treatment for an established infestation, and neither product is intended as routine prevention for healthy horses without wounds or an expectation of a wound.

• Ivermectin Liquid for Horses: a prescription oral solution authorized for short-term prevention when administered to a newborn foal within 24 hours of birth or to a horse of any age at initial wound care. FDA estimates the prevention window at no more than 24 hours.
• Dectomax/Dectomax-CA1: a doramectin injection authorized for prevention in horses one year of age or older when used at wound appearance or castration under the current directions.

FDA also maintains a current list of other emergency-authorized New World screwworm products. Availability, species, wound use, route, and legal conditions vary. Verify the current FDA materials and follow veterinary and animal-health direction.

Build prevention around wound control and fly pressure

• Find and address wounds promptly under veterinary direction.
• Bandage only when the location, wound type, heat, moisture, and veterinary plan make bandaging appropriate.
• Reduce manure buildup, wet organic matter, spoiled feed, and other fly-breeding pressure.
• Keep trailers, stalls, wash areas, and wound-care tools clean.
• Use only appropriately labeled repellents or barriers on suitable intact areas.
• Never pour ordinary fly products or harsh home remedies into open tissue.
• Inspect newborn navels and recent procedure sites at least daily, and more often when risk is elevated.

For general wound readiness, review the Horse First Aid Kit Checklist. For location and travel planning, use Regional Horse Care. The Horse Health Library remains the central route for additional practical care guidance.

Travel and showground decisions

Before loading a horse, verify current federal detections, active zones, state entry requirements, inspection timing, documentation language, treatment requirements, and destination rules. Requirements can change after a health certificate is issued.

Do a documented wound check before departure and again after arrival. Avoid hauling a horse with an unexplained draining or enlarging wound until a veterinarian has evaluated it. Do not assume an event remaining open means every horse or route is cleared for movement.

Frequently asked questions

The bottom line

Horse owners do not need to identify a fly or diagnose an infestation. They need to inspect wounds, recognize urgent warning signs, stop unnecessary movement, preserve useful evidence, and call the veterinary and animal-health chain quickly.

Emergency-authorized drugs add prevention tools for specific susceptible horses. They do not replace wound protection, fly management, reporting, or professional treatment.

Commercial disclosure: Draw It Out® publishes Horse Health Care News and sells equine-care products. No Draw It Out® product is promoted or recommended to prevent, diagnose, or treat New World screwworm.

Veterinary notice: This article is educational and does not replace examination, diagnosis, treatment, prescription instructions, reporting requirements, quarantine or movement directions, or current federal and state animal-health guidance.