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 potential threat posed by New World screwworm (NWS), a parasitic fly that can impact both human and animal health. While there have been no recent cases reported in Texas, state and federal agencies are preparing for the possible reintroduction of this parasite into the United States.
New World screwworm myiasis occurs when larvae of the Cochliomyia hominivorax fly infest wounds or mucous membranes of warm-blooded animals. The larvae feed on live tissue, causing pain and potentially severe tissue damage. According to DSHS, “People with NWS infestations may report pain and see or feel movement in the affected area. Larvae will drop to the ground after feeding to complete their lifecycle.”
The life cycle of NWS ranges from 14 to 54 days. Infestation does not spread directly from one host to another unless the fly’s life cycle is completed. The agency emphasized that awareness, surveillance, and control efforts are important for both humans and animals.
NWS was eradicated from the United States in the 1960s but remains endemic in most of South America, parts of the Caribbean, and southern Panama. In 2023, it was detected throughout Central America; Mexico reported detections beginning in November 2024.
Although there is currently no immediate risk within the United States, travel-related cases have occurred previously and continue to be a concern for travelers returning from regions where NWS is present.
Healthcare providers are advised to consider NWS infestation if patients present with very painful wounds containing visible larvae after traveling to affected areas. The advisory states: “Healthcare providers should consider NWS if their patient: Has recently traveled in areas with animal or human cases of NWS. Has a very painful and foul-smelling wound with visible larvae. Has a particularly deep wound with extensive tissue damage and evidence of larval infestation. Has an egg mass in or around a wound or opening.”
There is currently no approved medication for treating NWS infestation in humans; treatment involves removing all larvae—sometimes surgically—and monitoring for secondary bacterial infections.
Proper disposal procedures are critical: “Larvae should be removed and immediately placed into a leak proof container with 70% ethanol… Do not dispose of any larvae in the trash or outside in the ground.” Failure to follow these steps could lead to local introduction or spread of NWS.
Suspected cases must be reported immediately so samples can be sent for identification at DSHS laboratories in Austin before confirmation by CDC experts.
Travelers spending time near livestock or outdoors in regions where NWS is found face higher risks—especially those with chronic open wounds or certain medical conditions such as diabetes or immune system disorders. Preventive measures include wearing protective clothing, using insect repellents on skin and gear treated with permethrin, keeping wounds clean and covered, sleeping indoors behind screens when possible, and seeking prompt medical attention if larvae are observed.
For more information about local public health resources related to these precautions visit https://www.dshs.texas.gov/regional-local-health-operations/public-health-regions/texas-local-public-health
“People who see or feel larvae in or on their wounds should immediately contact their healthcare provider,” according to DSHS guidance.
