New World Screwworm Threatens US Livestock After Mexico Outbreak
A concerning development has emerged for American livestock producers as the New World Screwworm (NWS) fly, a pest considered eradicated from the United States since 1966, has resurfaced as a potential threat. This re-emergence follows a recent outbreak in Mexico, prompting immediate action from US authorities to safeguard the nation’s animal agriculture.
The gravity of the situation was underscored by the swift response of U.S. Department of Agriculture (USDA) Secretary Brooke Rollins. In a public announcement via social media platform X on Sunday, Secretary Rollins declared an immediate suspension of live cattle, horse, and bison imports through U.S. southern border ports of entry. This decisive measure aims to prevent the potential introduction and spread of the NWS fly within the United States.
Secretary Rollins emphasized the potential devastation that the NWS could inflict on the American cattle industry, drawing a stark comparison to the previous infestation that took three decades to overcome. The prevention of another such prolonged and costly recovery is clearly a top priority.
The New World Screwworm is a fly species endemic to several regions, including Cuba, Haiti, the Dominican Republic, and certain South American countries. According to the USDA’s Animal and Plant Health Inspection Service (APHIS), while the adult flies typically inhabit forests and wooded areas, they actively seek out hosts like cattle and horses in pastures and fields for reproduction.
The life cycle of the NWS fly is particularly gruesome and destructive. The female fly targets live, warm-blooded animals and lays her eggs in open wounds or natural orifices. Once hatched, the eggs develop into larvae, commonly known as maggots, which then burrow into the flesh of the host animal. This burrowing action causes extensive and potentially deadly damage.
The name "screwworm" is derived from the characteristic behavior of the maggots. Their method of burrowing into the flesh is similar to the way a screw is driven into wood, causing significant tissue damage and severe pain to the host. The maggots utilize sharp mouth hooks to tear at the host’s tissue, further enlarging the wound and attracting more flies to lay eggs, creating a vicious cycle of infestation.
While primarily a threat to livestock, the NWS can, in rare instances, infest humans. The Centers for Disease Control and Prevention (CDC) notes that individuals who travel to regions where the screwworm is prevalent, spend time around livestock animals, sleep outdoors, or have open wounds are at a higher risk of infestation.
These infestations can lead to myiasis, a parasitic infection characterized by the presence of fly larvae in human tissue. Myiasis is often extremely painful and can result in serious and potentially fatal damage to the affected individual. People who are immunocompromised, very young, very old, or malnourished are also at a heightened risk of contracting a screwworm infection. Similarly, those who have recently undergone surgery are at increased risk due to the presence of open sores, which serve as prime egg-laying sites for the flies.
The USDA has issued a stark warning regarding the potential consequences of another NWS outbreak in the United States. If the pest were to re-establish itself, pets, livestock, wildlife, and even humans would face the risk of suffering and dying from screwworm myiasis. The economic impact could also be substantial.
Historical data reveals the devastating impact of NWS infestations on the US livestock industry. During the 1950s and 1960s, livestock producers in the southwestern United States experienced annual losses estimated between $50 million and $100 million due to the screwworm. It was not until 1966 that the NWS was successfully eradicated from the country through intensive control and prevention efforts.
The significantly higher losses experienced in the Southwest during that era are attributed to several factors, including higher livestock populations, a larger geographic area, and a greater potential for the NWS to survive overwinter.
Despite the successful eradication in 1966, a localized outbreak occurred in the Florida Keys in 2016. However, this outbreak was quickly contained and eradicated by March 2017, primarily affecting the endangered deer population in the area. The swift response and eradication efforts demonstrated the ongoing vigilance and preparedness of the USDA.
The current outbreak in Mexico serves as a reminder of the ever-present threat posed by invasive pests and the importance of maintaining robust biosecurity measures. The temporary suspension of livestock imports from Mexico is a precautionary measure aimed at protecting the American livestock industry and preventing the re-establishment of the New World Screwworm in the United States. Continuous monitoring and proactive management are critical to mitigating the risk of future outbreaks and safeguarding the health and economic well-being of the nation’s animal agriculture sector.
