On June 3, 2026, the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the detection of a New World screwworm in Texas—the first of its kind in the country.
Officials identified worm larvae in the umbilical area of a 3-week-old calf. To date (6/4/26), there have been no further detections.
NWS is a serious pest that affects livestock, pets, wildlife, and less commonly, people and birds. NWS larvae (maggots) burrow into the flesh of living animals, causing serious damage to livestock and economic losses.
If the presence of screwworm is suspected in samples received at the University of Minnesota Veterinary Diagnostic Laboratory locations in St. Paul or Willmar, they will be forwarded to the National Veterinary Services Laboratory (NVSL) within 24 hours for evaluation.
Learn more about New World screwworm at Screwworm.gov.
Important Information On Sample Collection & Submission
Collecting and Submitting NWS Samples
Contact the State Animal Health Official to get a Foreign Animal Disease (FAD) number to coordinate the submission.
- Each animal infested gets their own labeled vial
- Submit eggs, larvae/maggots (various shapes and sizes), pupae, or adults (dry, no alcohol)
- Cover egg, larvae specimens with 70% ethanol or isopropyl alcohol, not formalin. Place adult flies dry in a plain tube
- With gloves and forceps, sample multiple sizes of larvae from different depths of the wound
- Take photos
Suspect NWS Infestation paperwork, 5-38 form
- Include FAD number in block 31:
“History or Additional Information”
Ask SAHO/AVIC - Please type or write legibly in permanent ink or pencil
Packaging
Please follow the instructions below for packaging samples.
| Packaging type | Descriptions and examples |
|---|---|
| Inner (primary) package, not full of liquid, held securely closed. | Vial with 70% ethanol or isopropyl alcohol covering the specimens, screw top or tight-fitting lid, vacutainer. No more than 30ml per package. No formalin! Label vials with permanent ink. Each animal gets their own vial. |
| Secondary package is sealable and contains absorbent material. | Example: Ziploc bag containing paper towels. |
| Outer package with 2 sides at least 4 inches long. No envelopes, no FedEx boxes. Withstands 9 ft. stackability + 6 ft. drop test. | Example: Sturdy cardboard box 4x4x3. Include paperwork 5-38 inside outside layer of box |
Ship to:
National Veterinary Services Laboratories
1920 Dayton Avenue
Ames, lA 50010
Overnight or Priority One white glove service (FAD) (Priority should be determined in consultation with AVIC and SAHO
Before or immediately after shipment, email: VS.DB.NVSL.DBRL.Parasitology@usda.gov
- In subject line, include phrase: “suspected screwworm”
- Email photos
National Veterinary Services Laboratories (NVSL) entomologists will acknowledge and give an informal report within 24 hours. An official report will be issued within three days.
This resource was produced by the University of Minnesota Veterinary Diagnostic Laboratory. For updates, refer to their New World Screwworm Disease Resources page.