Health Advisory: New World Screwworm Detected in the United States
HEALTH ALERT NETWORK
Health District 4
Advisory for Healthcare Providers
June 9, 2026
Health Advisory: New World Screwworm Detected in the United States
As of June 8, 2026, New World Screwworm (NWS), Cochliomyia hominivorax, has been confirmed in four livestock in Texas and one dog in New Mexico. NWS was eradicated from the United States over 60 years ago and its reemergence represents a significant concern for animal and public health.
NWS is a parasitic fly that lays eggs in wounds and body orifices. The larvae (maggots) feed on the living flesh of warm-blooded animals, including humans, pets, livestock, and wildlife. NWS infestation in people can be fatal if left untreated. Improper handling or disposal of larvae (e.g., allowing them to pupate in the environment) poses a risk for local establishment and spread in Idaho, which could have severe impacts on the health of animals in Idaho, people, and the economy.
Key Message: Healthcare providers should promptly recognize, report, and appropriately manage suspected NWS cases. Rapid identification and proper specimen handling are critical to prevent severe patient outcomes and establishment and spread of this parasite in Idaho.
Recommendations for Clinicians
Consider NWS infestation in patients presenting with:
- Visible larvae or egg masses in wounds or body orifices (e.g., ears, eyes, nose, mouth, genitals).
- Destruction of healthy tissue.
- Sensation of movement, foul odor, bloody discharge, swelling, and pain.
- Recent travel to regions where NWS is present (see https://www.aphis.usda.gov/animals/animal-health/livestock-and-poultry-disease/current-status?page=1)
Reporting
Immediately report all suspected human cases to Central District Health (208-327-8625), or the Idaho Department of Health and Welfare, Epidemiology Section (208-334-5939).
Specimen Collection and Submission
Collect and submit larvae from patients to the Centers for Disease Control and Prevention (CDC) for clinical diagnosis and confirmation.
- Collect at least 10 larvae (or all available if fewer than 10), including representative samples from multiple developmental stages if present
- Place in a leakproof vial with:
- 70% ethanol (preferred)
- OR =70% isopropyl alcohol
- OR 5–10% formalin
- Seal container securely (e.g., parafilm or tape)
For submission:
- Email dpdx@cdc.gov for specimen submission instructions
- Telediagnosis may be available:
https://www.cdc.gov/dpdx/resources/pdf/benchaids/nws-teledx-bench-aid-508.pdf
Treatment and Containment
Promptly remove and kill all remaining larvae and eggs from patients with suspected NWS infestation. Failure to kill and properly dispose of all larvae or eggs could result in introduction and establishment of NWS in the local environment.
- Use standard precautions when treating wounds and handling larvae.
- Place all remaining larvae and eggs in a leakproof container and fully submerge them in 70% ethanol (preferred). Isopropanol =70% is an acceptable alternative.
- Place the leakproof container in a zip-top plastic bag, seal it, and dispose in the trash.
Reexamine treated lesions after 24–48 hours to confirm no live larvae remain.
Additional Information
CDC. Clinical overview of New World screwworm https://www.cdc.gov/new-world-screwworm/hcp/clinical-overview/index.html
CDC. New World screwworm lifecycle https://www.cdc.gov/dpdx/newworldscrewwormmyiasis/index.html
CDC. Clinician Outreach and Communication Activity: Resurgence of New World Screwworm in the Americas: What Healthcare Providers Need to Know (CE available) https://www.cdc.gov/coca/hcp/trainings/resurgence-new-world-screwworm.html
CDC. Prevention of New World screwworm infestation https://www.cdc.gov/new-world-screwworm/about/index.html#cdc_disease_basics_prevention-prevention
USDA: Stop Screwworm: Unified Government Response to Protect the United States https://www.aphis.usda.gov/animals/animal-health/livestock-and-poultry-disease/stop-screwworm
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