The return of the screwworm
Screwworms were once endemic in the US, but were eradicated in the 1960s amid a concerted effort to wipe out their population. This is done by aerial bombardment of sterile male flies, which is the most effective weapon against parasites. The mass release of false stallions displaces fertile males, preventing them from mating with females, who generally only mate once.
With this method, called the Sterile Insect Technique, the flies were eradicated not only from the United States, but from all of Central America. They were declared eradicated from Panama in 2006.
Until recently, the screwworm population was kept in check by a biological barrier along the Darien Gap on the border between Panama and Colombia. The USDA partnered with Panamanian authorities to build a sterile fly production facility in the gap to release sterile flies regularly and maintain the line. But in 2022, the barrier was broken and the flies have buzzed incessantly north ever since.
In response, the United States has expanded surveillance and capture efforts in Texas. It is also building a $750 million sterile fly production facility in South Texas. The USDA says it is currently dispersing 100 million sterile insects per week in Mexico and along the US-Mexico border to prevent the flies from advancing further.
In Wednesday night’s news release, the USDA said it will release sterile flies through ground release chambers in the area around the detection. This is in addition to the 4 million flies that have already been released by air in the area this week.
“The United States has defeated this pest before and we will do it again,” Dudley Hoskins, USDA undersecretary for marketing and regulatory programs, said in the news release.
This post was updated at 10:45 pm ET to reflect that the USDA confirmed a northwest screwworm infection.
