Maryland Detects First U.S. Human Screwworm Case, Stirring Livestock Concern

U.S. health and agriculture officials are investigating the nation’s first confirmed human case of New World screwworm after a Maryland resident who recently travelled from Guatemala was diagnosed with the flesh-eating parasite, according to multiple sources familiar with the matter. The Centers for Disease Control and Prevention privately confirmed the infection last week, and the Maryland Department of Health oversaw treatment, the sources said. The New World screwworm is a parasitic fly whose larvae burrow into the flesh of warm-blooded animals. While human infections are rare and usually survivable with prompt care, the insect can devastate livestock herds if it becomes established. The Maryland case is the first sign of the pest in the United States since an outbreak began spreading north from Central America in 2023. Livestock groups warned the discovery could unsettle already tight beef and cattle futures markets. Analysts estimate an uncontrolled outbreak in Texas alone could cost about $1.8 billion in animal losses, labour and medication. The U.S. cattle herd is at its smallest in seven decades, heightening market sensitivity to disease threats. The incident has renewed criticism of the U.S. Department of Agriculture’s preparedness. Agriculture Secretary Brooke Rollins this month announced plans for a sterile-fly production facility at Moore Air Force Base in Edinburg, Texas, but the plant is two to three years from operation. Border restrictions on Mexican cattle imports remain in place, and Mexico is building its own $51 million sterile-fly plant to slow the parasite’s advance.