The Texas Department of State Health Services (DSHS) has issued a health advisory to alert public health professionals, clinicians, and the public about the potential reintroduction of New World screwworm (NWS) into the United States. While no recent cases have been reported in Texas, DSHS is urging vigilance among healthcare providers, especially for patients who have traveled to areas where NWS is present.
New World screwworm myiasis is caused by the larvae of Cochliomyia hominivorax, a fly that feeds on live tissue. The infestation starts when the fly lays eggs near wounds or mucous membranes such as the nose, ears, or mouth of warm-blooded animals. Once hatched, larvae feed on living flesh and cause pain and tissue damage before dropping to the ground to complete their lifecycle.
According to DSHS, “NWS infestation cannot spread from one host to another without the completion of the fly’s life cycle, which ranges from approximately 14-54 days. NWS has the potential to significantly affect local animal populations, so awareness, surveillance, and control of NWS myiasis and C. hominivorax flies in both animals and humans are critical.”
The parasite was eradicated from the U.S. in the 1960s but remains endemic in much of South America, parts of the Caribbean, and southern Panama. In 2023, it was detected throughout Central America and then found in Mexico starting November 2024.
While there is no immediate risk within the United States, travel-related cases remain possible. People with NWS infestations may experience significant pain at wound sites along with foul odors and visible larvae.
There is currently no approved medication for treating NWS infestations in humans; treatment involves removing all larvae from wounds. Sometimes surgical removal is necessary because larvae can burrow deep into tissue. DSHS notes that secondary bacterial infections are possible and should be monitored by healthcare providers.
Proper handling and disposal of removed larvae are critical to prevent environmental contamination: “Larvae and eggs should be killed by placing them into a leak-proof container with 70% ethanol. The volume of liquid in the container should be enough to fully submerge the larvae. Do not dispose of extracted larvae or eggs in the trash or on the ground without first killing the larvae.”
Diagnosis relies on identifying morphological features of collected larvae. All suspected cases must be reported immediately so samples can be sent to DSHS laboratories for identification and confirmation by federal agencies such as CDC.
Travelers who spend time around livestock or outdoors in regions where NWS is present—including Mexico, Central America, South America, and some Caribbean countries—may face higher risk. People with chronic wounds or weakened immune systems are particularly vulnerable.
DSHS recommends precautions such as wearing long clothing to limit insect bites, using products containing permethrin on clothes and gear, keeping wounds clean and covered (https://www.dshs.texas.gov/regional-local-health-operations/public-health-regions/texas-local-public-health), sleeping indoors with screens when possible, and seeking prompt medical attention if signs of infestation appear.
For further questions about reporting conditions related to NWS or for consultation regarding clinical management or zoonosis control issues, contact your local health department or DSHS Zoonosis Control Branch.
