A human case of the New World screwworm has emerged in the United States, prompting federal officials to take immediate action to prevent this parasitic threat from affecting the food supply. This marks the first recorded infestation in a human within the country in years. The U.S. previously faced significant challenges with New World screwworms (NWS) and has recently taken measures to safeguard livestock as the parasite approaches the southern border.
In November 2023, the U.S. Department of Agriculture (USDA) closed the southern border to livestock imports due to concerns regarding potential infestations. According to the U.S. Food and Drug Administration (FDA), under an emergency use authorization, animal drugs can now be utilized to treat or prevent infestations, specifically noting that the authorization pertains solely to animal medications. The FDA stated, “Although eradicated from North America and Central America decades ago, NWS has progressed north since 2022 and is now approaching the U.S. border with Mexico. This parasite poses an emerging threat to livestock and food security, with potential impacts on both national security and animal health.”
Health and Human Services Secretary Robert F. Kennedy Jr. emphasized the urgency of the situation, stating, “Today we are taking decisive action to safeguard the nation’s food supply from this emerging threat.” He further noted that the FDA’s authorization empowers them to act swiftly to limit the spread of the New World screwworm and to protect American livestock.
Understanding the New World Screwworm
New World screwworms are larvae of the New World screwworm fly, which can lay eggs in the wounds of warm-blooded animals. Once hatched, the larvae burrow deeper into the flesh, causing severe damage that can lead to death if untreated. The USDA highlights that these parasites can affect various animals, including livestock, pets, and even humans in rare cases. The Centers for Disease Control and Prevention (CDC) notes that NWS is endemic to regions in South America and the Caribbean, and the larvae can also infiltrate body cavities with mucous membranes, such as nasal passages.
The recent human case involved a Maryland resident who may have contracted the infestation during international travel, possibly to El Salvador or Guatemala. This incident is linked to an ongoing outbreak in Central America. The CDC has stated that there is currently no specific treatment other than prevention and the rapid removal of the larvae.
Combatting the Screwworm Threat
In response to the rising concern regarding New World screwworms, Secretary of Agriculture Brooke Rollins recently announced plans for a significant investment of up to $750 million to establish a facility in Texas that will produce sterile flies. This method has proven effective in managing screwworm populations in the past. Governor Greg Abbott of Texas warned that an infestation could severely impact the state’s cattle industry, potentially costing up to $1.8 billion to the economy and driving up beef prices.
Following the closure of the U.S. border to livestock imports, officials acknowledged the risk that the screwworm could cross the border through natural wildlife movement. To address these concerns, the U.S. and Mexican governments agreed in February to a comprehensive pre-clearance inspection and treatment protocol to protect trade and mitigate the spread of the fly’s larvae.
A facility at Moore Airbase in Texas is set to become a production site for sterile flies, with an expected output of up to 300 million sterile flies per week. This facility will collaborate with similar operations in Panama and Mexico, where the USDA has allocated $21 million for renovations aimed at enhancing sterile fly production by an additional 60 to 100 million flies.
Historically, sterile flies have been utilized effectively to combat screwworm infestations since the 1960s. The method involves releasing sterile males that mate with wild females, resulting in no offspring and gradually reducing the screwworm population.
The appearance of New World screwworms in humans, while rare, serves as a reminder of the potential risks posed by this parasite. Infestations can lead to significant health issues, including severe irritation, foul odors, and visible maggots in wounds. A similar case reported in Mexico was successfully treated with antibiotics after the larvae were removed, highlighting the importance of rapid response in managing such infections.
As federal officials continue to monitor the situation closely, the emphasis remains on protecting both public health and the agricultural industry from the threats posed by the New World screwworm.
