Following a resurgence of the New World Screwworm (NWS) in Mexico, the U.S. Department of Agriculture (USDA) has imposed a temporary halt on cattle, horse, and bison imports from the southern border. This decision was made to mitigate the risk of the parasitic fly, historically eradicated in the U.S. since 1966, from re-entering and spreading to American livestock. USDA Secretary Brooke Rollins declared the suspension effective immediately, citing the potential devastation that a recurrence of the NWS could bring.
According to the USDA’s Animal and Plant Health Inspection Service (APHIS), the NWS is endemic to regions such as Cuba, Haiti, the Dominican Republic, and parts of South America. Though the flies primarily inhabit forested areas, they often target warm-blooded hosts like cattle and horses in open fields. The female fly lays eggs in wounds or orifices, leading to the hatching of larvae that burrow into the host’s flesh, causing extensive tissue damage and potentially fatal myiasis infections. The CDC notes that while rare, the larvae can also infest humans, particularly those with open wounds, immunocompromised conditions, or recent surgical procedures.
The USDA’s move has significant implications for the U.S. livestock industry, which suffered an estimated $50 million to $100 million in annual losses during the 1950s and 1960s due to the NWS outbreak before it was successfully eradicated. While the last significant outbreak in the U.S. was contained in the Florida Keys in 2016, the current situation has raised concerns about the potential for economic damage if the NWS is not contained. The shutdown of imports has already disrupted trade and may affect markets for livestock and related products.
The NWS’s emergence in Mexico has sparked a multi-agency response, with federal officials working to bolster border controls and implement prevention strategies. The CDC is also advising travelers and outdoor enthusiasts to take precautions, especially in regions where the fly is known to be prevalent. Given the potential for the NWS to affect both animals and humans, the USDA’s decision underscores a broader effort to protect public health and the agricultural economy from the threat of this invasive species.
As authorities intensify their efforts to monitor and prevent the spread of the NWS, the focus remains on minimizing the impact on livestock and safeguarding human health. The situation highlights the ongoing challenges of managing invasive biological threats and the importance of international cooperation in disease prevention. With the risk of further outbreaks, the U.S. is preparing for a potential resurgence of a pest that once posed a major economic and health crisis.