U.S. Struck by Flesh-Eating Parasite: First Human Case Confirmed in Maryland

A Case with Far-Reaching Consequences

For the first time in modern American history, health authorities have confirmed a human case of the dreaded New World screwworm—a flesh-eating parasite that previously decimated cattle herds in North and Central America. The case was detected in Maryland in a traveler returning from El Salvador. The parasite, potentially deadly, was identified by the Centers for Disease Control and Prevention (CDC) on August 4.

According to officials, the risk of further human transmission is considered low. However, the news has caused anxiety in the cattle industry—especially since screwworm was eradicated from the U.S. in the 1960s through an extensive campaign using sterile flies.

Economic Threat to Texas and the Cattle Industry

The USDA estimates that a potential screwworm outbreak in Texas alone could cost up to $1.8 billion. Texas is America’s largest cattle producer, and the industry is already under pressure from record-high prices and reduced herds.

In response, Agriculture Secretary Brooke Rollins has launched a plan to build a new facility in Texas for producing sterile flies—the only known method to control the parasite. However, this initiative could take up to three years to become operational. Criticism has therefore not been far behind:

“We found out through indirect channels and had to contact the CDC ourselves to get answers,” says Beth Thompson, State Veterinarian for South Dakota.

A Parasite with Corkscrew Terror

Screwworm refers to the larvae of a parasitic fly that lays its eggs in open wounds on both humans and animals. When the eggs hatch, the larvae burrow into living tissue—a process that is not only painful but can also be fatal if not detected in time.

Although screwworm usually affects animals, humans can also become infected. Treatment involves manually removing hundreds of larvae and disinfecting the wound.

Border Closures and Global Escalation

Since November 2024, the U.S. has effectively halted the import of cattle from Mexico—a measure aimed at curbing the spread from the south, where screwworm is gaining ground. Mexico has responded by constructing a new facility for sterile flies at a cost of $51 million.

The existing facility in Panama can produce 100 million sterile flies per week. But according to the USDA, five times that amount is needed to push the parasite population back to the Darien jungle between Panama and Colombia.

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