FDA clears emergency use of drugs as screwworm nears US border

USA – The United States has taken emergency steps to shield its cattle industry from the looming threat of the New World screwworm, a flesh-eating parasite last eradicated from the country nearly six decades ago. 

On 19th August, federal health officials said the Food and Drug Administration (FDA) has been given authority to fast-track the use of animal drugs to prevent or treat screwworm infestations, even if those drugs are not formally approved for that purpose in the US.

The move follows a declaration by the Department of Health and Human Services (HHS), which allows the FDA to issue Emergency Use Authorizations (EUAs) for animal drugs in the face of potential outbreaks. 

“The risk to human health in the United States remains very low, but the potential future threat to animal populations and the food supply chain requires proactive action,” the FDA said.

Parasite spreads in Mexico

The screwworm, a parasitic fly that lays eggs in wounds and consumes the living tissue of livestock, pets, wildlife, and even humans, was detected in Mexico last month, about 370 miles from the US border. 

The discovery prompted the US Department of Agriculture (USDA) to indefinitely halt imports of Mexican cattle, tightening supplies in an already strained beef market.

Although the US has not confirmed a screwworm case in decades, ranchers and officials fear its return could decimate herds and drive beef prices higher. 

The USDA describes screwworm as a “devastating pest” and notes that untreated cases can be fatal. Ranchers in Texas and the southern border states are on high alert as surveillance intensifies.

Drugs and sterile flies

So far, there are no FDA-approved drugs for screwworm treatment in the US. However, under the new EUA pathway, veterinarians and ranchers may soon gain access to medicines used abroad or products approved domestically for other parasites. 

Tristan Colonius, chief veterinary officer for the FDA’s Center for Veterinary Medicine, said the agency is reviewing data on drugs such as ivermectin and assessing which products could be deployed most quickly. 

“If screwworm is found in US animals soon, an important part of the response would involve using drugs in ways that are not in line with their label directions,” Colonius explained.

At the same time, Washington is investing heavily in the sterile insect technique, the long-standing strategy credited with eradicating screwworm in the 1960s. 

The USDA announced plans to spend US$750 million to build a new production facility in southern Texas, just 20 miles from the Mexican border. Once operational, it is expected to release up to 300 million sterile flies per week to overwhelm wild populations.

“This terrible pest is threatening American cattle production,” Agriculture Secretary Brooke Rollins said. “We must construct an additional sterile fly production facility in the United States to stop the northward advancement.”

Mounting costs and global concern

The screwworm threat comes at a time when the US cattle herd is already at a 75-year low, pushing beef prices to record highs. Experts estimate that Texas alone could face as much as US$1.8 billion in damages if the pest takes hold.

Global agencies are also sounding the alarm. The World Organisation for Animal Health has called the parasite’s reappearance in Central America a “worrying development” for animal health, human health, and biodiversity. 

Belize recently confirmed its first human case, while Mexico continues to battle outbreaks in livestock and pets.

Despite the urgency, experts warn that the US and Mexico must dramatically expand sterile fly production to slow the spread. Current facilities in Panama can only produce a fraction of the sterile insects needed.

“This might be the worst biological outbreak that we’re facing in our lifetime,” said Freddy Nieto, manager of El Sauz Ranch in South Texas. “We’ve faced the New World screwworm before and succeeded. With collective action, we can do it again.”

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