USDA Confirms Flesh-Eating Screwworm in Texas Calves

The U.S. Department of Agriculture (USDA) confirmed on June 3 that a three-week-old calf in Zavala County, Texas, near the Mexican border, had been infected by the New World screwworm. Two days later, a second case was detected in a one-month-old calf in the same county, just 5.6 miles from the first confirmed case. The New World screwworm, or Cochliomyia hominivorax, is a parasitic fly whose larvae burrow into living flesh, unlike typical maggots that feed on decaying matter. The USDA has been monitoring the fly’s movement, which has been steadily advancing north from Central America to Mexico since 2023. As of June 5, no additional cases had been reported in the U.S., but Mexico’s border states of Nuevo León and Tamaulipas had over 200 active infestation cases last month, with more than 2,000 cases nationwide. The USDA stated it was prepared to contain the outbreak, citing prior efforts to delay its arrival. The potential economic impact of the screwworm could be significant for livestock industries, particularly in regions near the border.