Context:

New World screwworms, a flesh-eating larval form of the blow fly Cochliomyia hominivorax, have been spreading in Central America since early 2023, posing a significant threat to livestock in the region. This parasitic insect targets warm-blooded animals, laying eggs in wounds, which then hatch into larvae that feed on living tissue, causing severe damage and even death if untreated. The United States previously eradicated this pest in the 1960s and 1970s using a method of sterilized male flies, which are released to mate with wild females, preventing reproduction. With the recent spread to southern Mexico, US officials plan to establish a new facility near the Texas-Mexico border to produce sterilized flies for aerial dispersal, a costly but necessary measure to protect the multimillion-dollar livestock industry. The new facility is part of a broader strategy, including reopening livestock trading ports and renovating an old fly production plant in Mexico, to combat the screwworm threat effectively.

Dive Deeper:

• New World screwworms are the larval stage of Cochliomyia hominivorax, a fly species that uniquely feeds on the flesh of living animals, unlike other blow flies that consume dead tissue. These larvae cause significant harm by burrowing into the tissue of their hosts, creating large wounds that can lead to severe health issues or death if left untreated.

• The current outbreak, which started in early 2023, has affected several Central American countries, marking the first such occurrence in over two decades. The spread of screwworms has reached southern Mexico, prompting concerns in the United States about potential impacts on livestock and the need for preventive measures.

• Historically, the US successfully eradicated screwworms in the 1960s and 1970s using a strategy of releasing sterilized male flies to reduce the population through unsuccessful mating. This method relies on breeding large numbers of sterile flies, which are then dispersed to mate with wild females, preventing further reproduction.

• To counter the current threat, the US Department of Agriculture plans to open a new facility near the Texas-Mexico border to produce sterilized flies, an effort estimated to cost around $300 million. This 'fly factory' is crucial for producing the hundreds of millions of sterile flies needed to slow and eventually eliminate the outbreak.

• The economic impact of screwworm infestations is substantial, with potential losses to the livestock industry estimated at $10 billion. The planned initiatives, including the new fly production facility and reopening of livestock trading ports, are seen as vital investments to protect this critical sector.

• In addition to the new facility, the USDA has announced plans to renovate an old fly factory in Mexico by late 2025, further enhancing the capacity to produce sterile flies. This coordinated effort aims to control the spread of screwworms across affected regions in Central America and prevent their northward migration into the US.

• Surveillance and preventive measures remain key to managing the screwworm threat, particularly in rural areas where these flies are more likely to thrive. Ranchers are advised to monitor livestock closely and avoid activities that create wounds susceptible to screwworm infestations during warmer months when flies are more active.