First U.S. Human Case of Rare Flesh-Eating Parasite New World Screworm Confirmed Amidst Growing Concerns for Livestock Industry

The United States has confirmed its first human case of New World screwworm, a parasitic infestation caused by fly larvae that primarily affects warm-blooded animals. This development comes after the parasite’s recent northward migration from South America, causing concern for the nation’s cattle industry.

The Centers for Disease Control and Prevention (CDC) confirmed the case on August 4 in a patient who had recently traveled to El Salvador. According to Health and Human Services spokesperson Andrew Nixon, this is the first human case of New World screwworm myiasis identified in the United States from an outbreak-affected country. The risk to public health is currently deemed low.

The New World screwworm is typically found in South America and the Caribbean. It infests animals by laying its eggs in wounds or other entry points, with females capable of laying up to 200 eggs at a time. The larvae feed on the tissue or flesh of the host, making their way into vulnerable areas such as the brain or causing the wound to become large and potentially leading to sepsis.

However, it is important to note that New World screwworm is not contagious between humans. Instead, it poses a significant risk to livestock. In the past year, the pest has been detected in cattle farms in Mexico, raising concerns about its proximity to the U.S. border.

In response, federal authorities have taken steps to eliminate the threat, including the use of the sterile insect technique pioneered by the USDA in the 1950s. This method involves mass-rearing and sterilizing insects with radiation before releasing them to prevent reproduction. Through this approach, the U.S. successfully eradicated New World screwworm in 1966, a feat repeated by Mexico in the 1970s and Central America in the early 2000s.

Recent cases have been documented in Panama, Costa Rica, Nicaragua, and Honduras, fueling concerns of a northward spread. To combat this threat, the USDA has announced plans to build the country’s only sterile fly production facility at an air force base in Edinburg, Texas, capable of producing up to 300 million sterile flies per week.

Agricultural groups have expressed concern about the potential impact of a contemporary outbreak on the supply chain, estimating a total economic loss of over $10.6 billion. The USDA has also announced plans to hire mounted patrol officers for border surveillance, train dogs to detect screwworm infestations in livestock at the border, and invest $100 million in technologies to combat screwworm.

The introduction of New World screwworm in the U.S. could further complicate an already volatile cattle market, according to agricultural groups. The USDA’s proactive measures are intended to prevent this scenario and protect both public health and the nation’s livestock industry.