Quick Read
- The US confirmed its first travel-associated screwworm case in decades.
- The patient, a Maryland resident, contracted the parasite in El Salvador.
- Screwworm poses a major threat to livestock, with potential $1.8 billion losses in Texas alone.
- The USDA is constructing a sterile fly facility in Texas to combat the parasite.
The United States has confirmed its first travel-associated case of the flesh-eating New World screwworm parasite in decades. The infected individual, a Maryland resident, was diagnosed after returning from El Salvador. While the case was identified early and treated successfully, it has reignited concerns about the parasite’s potential to devastate livestock and wildlife, as well as its implications for public health and agriculture.
What Is the New World Screwworm?
The New World screwworm is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. Female flies lay eggs in open wounds, and once hatched, the larvae burrow into the flesh, causing severe damage. The parasite gets its name from the larvae’s screw-like motion as they burrow deeper into the host’s tissue. If left untreated, infestations can be fatal, especially in livestock. According to the Centers for Disease Control and Prevention (CDC), human cases are rare but can occur in regions where the parasite is endemic.
Historically, screwworms were eradicated from the United States in the 1960s through a sterile insect technique. However, the parasite remains a significant problem in parts of Central and South America, and its recent northward spread has raised alarms.
The Maryland Case: A Rare Occurrence
The Maryland Department of Health and the CDC confirmed the case on August 4, 2025, after analyzing images of larvae submitted by the patient. The individual had recently traveled to El Salvador, a country experiencing an outbreak of screwworm. While early reports from Reuters suggested the patient might have traveled from Guatemala, officials later clarified that El Salvador was the source.
Andrew G. Nixon, a spokesperson for the U.S. Department of Health and Human Services, stated, “This is the first human case of travel-associated New World screwworm myiasis from an outbreak-affected country identified in the United States.” Nixon emphasized that the risk to public health remains very low due to the isolated nature of the case.
The patient received prompt medical attention, which involved the removal of larvae and wound disinfection. According to Türkiye Today, privacy laws have restricted the release of further details about the individual’s condition.
Agricultural and Economic Implications
While human cases are rare, the potential impact of screwworm on livestock is enormous. The U.S. Department of Agriculture (USDA) estimates that an outbreak in Texas, the nation’s largest cattle-producing state, could cost $1.8 billion in livestock deaths, labor, and medication expenses. Livestock producers have expressed frustration with the federal government’s response to the parasite’s spread.
Beth Thompson, a state veterinarian from South Dakota, criticized the CDC for its lack of transparency, stating, “We found out via other routes and then had to go to CDC to tell us what was going on. They weren’t forthcoming at all.” This sentiment reflects growing concerns within the agricultural community about the government’s preparedness to handle a potential outbreak.
In response, Agriculture Secretary Brooke Rollins recently announced the construction of a sterile fly production facility in Texas to combat the screwworm. This technique, which was instrumental in eradicating the parasite in the past, involves releasing sterile male flies to disrupt the breeding cycle.
Lessons from History and Future Precautions
The eradication of screwworm in the U.S. during the 1960s was hailed as a major agricultural achievement. However, the parasite’s resurgence in Central and South America underscores the importance of vigilance and preventive measures. The CDC and USDA are working closely with state and international partners to monitor the situation and prevent further introductions of the parasite into the U.S.
Public health experts stress the importance of education and awareness, particularly for travelers to outbreak-affected regions. Simple precautions, such as covering wounds and seeking prompt medical attention for unusual symptoms, can significantly reduce the risk of infection.
The confirmation of this case serves as a reminder of the interconnectedness of global health and agriculture. While the immediate threat to the U.S. remains low, proactive measures are essential to safeguard both public health and the economy.