The Texas Department of State Health Services (DSHS) has issued a health advisory to alert public health professionals, clinicians, and the general public about the New World screwworm (NWS), a parasitic fly that poses risks to both humans and animals. While no recent cases have been detected in Texas, authorities are preparing for the possible reintroduction of this parasite into the United States.
The New World screwworm, scientifically known as Cochliomyia hominivorax, causes myiasis through its larvae feeding on live tissue. The fly lays eggs near wounds or mucous membranes such as the nose, ears, or mouth of warm-blooded animals. Once hatched, larvae begin feeding within a day. People affected by NWS may experience pain and notice movement in the wound area. After feeding, larvae drop to the ground to complete their lifecycle.
The spread of NWS requires completion of its life cycle, which can last from 14 to 54 days. Due to its potential impact on animal populations, DSHS emphasizes the importance of awareness and surveillance for both human and animal cases.
The United States eradicated NWS in the 1960s; however, it remains endemic in much of South America, parts of the Caribbean, and southern Panama. In 2023, NWS was detected throughout Central America and began appearing in Mexico from November 2024 onward.
There is currently no immediate threat within the United States but travel-related cases remain possible. Those with recent travel history to areas where NWS is present should be especially vigilant.
Symptoms include painful wounds that enlarge over time and emit a foul odor. Several hundred larvae may be visible within days after hatching. The larvae can grow up to approximately two-thirds of an inch long.
Healthcare providers are advised to consider NWS when treating patients who have traveled in affected regions and present with painful wounds containing visible larvae or egg masses. There is currently no approved medication for treating human infestations; instead, all larvae must be removed manually—sometimes surgically—to prevent further tissue damage and secondary bacterial infections.
Larvae should be killed by submerging them in 70% ethanol before disposal according to medical waste protocols. Improper disposal could result in environmental contamination and reintroduction of NWS locally.
Diagnosis relies on identifying specific features of extracted larvae collected from different depths within wounds. All suspected cases should be reported immediately so samples can be sent to DSHS laboratories for confirmation by the Centers for Disease Control and Prevention (CDC). Public health consultation is available through local health departments coordinating with DSHS.
Travelers spending extended periods around livestock or outdoors in regions with known NWS presence face increased risk—especially those with chronic wounds or weakened immune systems. Preventive measures include wearing protective clothing such as long sleeves and pants, treating clothes with permethrin products, keeping wounds clean and covered, sleeping indoors or using screened rooms, and minimizing exposure to insects outdoors. Local public health information is available at https://www.dshs.texas.gov/regional-local-health-operations/public-health-regions/texas-local-public-health.
Anyone noticing larvae in their wounds should seek medical attention immediately rather than attempting self-removal.
###
