US releases flies in Panama to combat dangerous worm infestation

The Trump administration agreed with the government of José Raúl Mulino to release millions of flies in Panama to try to extinguish a pest that threatens livestock and rural areas of the Central American country.

Specifically, 14 million flies, all male, will be released each week in locations such as the Panamanian jungle.

The aim is to control and wipe out a plague of the Cochliomyia hominivorax or the cattle screwworm, an insect larvae endemic to the region that is capable of causing serious health problems in both animals and humans when it infiltrates their skin.

The released flies will act as a barrier to combat the proliferation of the cattle screwworm. Being male, they will prevent reproduction.

Both governments are working together through the Panama-United States Commission for the Eradication and Prevention of the Screwworm (COPEG), created in 1994. The Department of Agriculture (USDA) is a member of this group.

A reason to block imports

According to detailed COPEG, at the beginning of 2025 there were 24,696 positive cases of infection by the cattle screwworm, called "myiasis," in Panama. Other countries in the region also had cases: Costa Rica (13,014), Nicaragua (9,279), Honduras (311), Guatemala (89), Mexico (three), El Salvador (two) and Belize (two).

Despite the fact that, for the moment, there were few cases of infection, Secretary of Agriculture Brooke Rollins warned that cattle imports from Mexico to the United States could be blocked if the plague is not controlled, sending a formal letter to the Mexican government.

Mexican President Claudia Sheinbaum reacted by calling Rollins' warning "excessive." "There are things [in the letter] that are right, [such as] collaboration, coordination, and others we consider to be excessive," she said, in statements picked up by AFP.

According to the Centers for Disease Control and Prevention (CDC), the cattle screwworm usually settles in open wounds or body cavities, where it causes infections. At this time, there is no specific method to extinguish the pest, so assets such as flies are used to try to control it.

The CDC asks that, if larvae are found, they should be killed and placed in high-proof ethyl alcohol.