US confirms nation’s first travel-associated human screwworm case connected to Central American outbreak 

The first human case of travel-associated New World screwworm has been reported in the United States by the US Department of Health and Human Services. The case was confirmed by the CDC and involved a patient who had recently traveled to El Salvador. This news comes amidst concerns from the beef industry about the potential spread of the flesh-eating parasite.

Screwworms are parasitic flies that lay eggs in wounds on warm-blooded animals. Once the eggs hatch, the larvae burrow through living flesh, causing serious harm and potentially death if left untreated. The CDC has confirmed a case in Maryland, but there are conflicting reports about the source of the infection.

The US government has not confirmed any cases in animals this year, but the industry is on high alert due to the potential economic impact of a screwworm outbreak. The USDA estimates that an outbreak could cost the economy in Texas, the largest cattle-producing state, about $1.8 billion in losses.

Efforts are being made to combat the spread of screwworm, including the construction of a sterile fly facility in Texas. Mexico has also taken steps to limit the spread of the pest, with a new facility being built in the country’s south. The USDA has estimated that 500 million sterile flies would need to be released weekly to push the fly back to the Darien Gap, the rainforest stretch between Panama and Colombia.

Screwworms have been moving north through Mexico since 2023 and are endemic in several countries in the region. The US has halted livestock trade through southern ports of entry to prevent the spread of the parasite. The last major outbreak of screwworm in the US was eradicated in the 1960s through the release of sterilized male flies.