By Marie Rosenthal, MS
The FDA grants emergency use authorizations (EUAs) for animal drugs to treat or prevent infestations caused by the New World screwworm (NWS) in response to outbreaks in Mexico and Central America.
This declaration applies only to veterinary medications.
Although eradicated from North and Central America decades ago, NWS has progressed north since 2022 and is now approaching the U.S. border with Mexico. This parasite poses a threat to livestock and food security. In 2023, NWS detections in Panama increased from an average of 25 cases per year to more than 6,500 in one year. Since then, screwworm has been detected in Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador and Mexico, north of the biological barrier that has successfully contained this pest to South America for decades.
The FDA provides information for veterinarians about treating this disease, which includes a list of medications that can be used off-label.
U.S. Secretary of Agriculture Brooke L. Rollins recently announced a Department of Agriculture plan to combat NWS. NWS is a devastating pest. When NWS maggots burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal. NWS can infest livestock, pets, wildlife, occasionally birds and, in rare cases, people.
While USDA is coordinating efforts to combat NWS, it will require continued collaboration between federal agencies, state governments and the private sector.
NWS is endemic in Cuba, Haiti, the Dominican Republic and countries in South America. For decades, the United States and Panama have collaborated through the Commission for the Eradication and Prevention of Screwworm to prevent the pest’s northward movement using a biological control technique (sterilized insects) to eradicate NWS fly populations. This approach eradicated NWS from the United States in 1966 and eliminated a small outbreak from the Florida Keys in 2017.
“We are taking decisive action to safeguard the nation’s food supply from this emerging threat,” said Health and Human Services Secretary Robert F. Kennedy Jr., about the FDA’s EUA. “This authorization equips FDA to act quickly, limit the spread of New World Screwworm, and protect America’s livestock.”
Currently, there are no FDA-approved drugs for NWS in the United States. The FDA through an EUA can authorize the flexible, faster use of certain animal drug products that may be approved for other purposes, or available in other countries, but not formally approved for NWS in the United States. This ensures veterinarians, farmers and animal health officials have timely access to the tools they need to protect pets, livestock and the nation’s food supply.
“This emergency use authorization is another tool we can use in the fight against New World Screwworm,” Ms. Rollins said. “Stopping this pest is a national security priority.”
The FDA will provide future guidance to veterinarians and stakeholders on the appropriate use of any products authorized for emergency use and update the New World Screwworm: Information for Veterinarians page.
An economic analysis of the 1976 NWS outbreak in Texas indicated that more than 1.48 million cattle and 332,600 sheep and goats were infested with NWS that year. Assuming equivalent livestock populations and NWS infection rates as in the case study in 1976 Texas, the results in inflation-adjusted 2024 numbers indicate that an NWS outbreak roughly the scale of the 1976 outbreak could cost Texas producers $732 million per year and the Texas economy a loss of $1.8 billion, according to a USDA report.
Numerous factors make this comparison, more than 40 years after NWS eradication, difficult. Texas’ cattle population in 2024 is significantly larger (12 million), while the sheep and goat populations are lower (655,000).
