COAHUILA — A New World screwworm was detected in a 5-year-old goat in Mexico's Coahuila state, 25 miles from the U.S. border. A second case was found in a 6-month-old sheep in the same state, 31 miles from the border.
U.S. officials have tracked 32 cases of the New World screwworm in Coahuila, including 19 active infections. Nationally, at least 26,216 cases have been identified across Mexico, with more than 2,700 currently active. The U.S. Department of Agriculture states that the New World screwworm "is not currently present" in the United States and that "the current risk to livestock, other animals, and people in the United States remains very low."
The New World screwworm is a parasitic fly that lays its eggs in open wounds or orifices such as the eyes, ears, nose, or mouth, and the larvae consume living tissue after hatching. The parasite is typically found in South America and parts of the Caribbean but has been detected increasingly farther north in Central America and Mexico over the last three years.
The U.S. has blocked cattle imports from Mexico for over a year to prevent the spread of the New World screwworm. An outbreak in the U.S. could cause $1.8 billion in damage to Texas' economy alone, according to a USDA estimate.
In April, the screwworm was found in Mexico 60 miles from the U.S. border. In late 2024, the Texas Parks and Wildlife Department issued an advisory after the parasite was detected in a cow in southern Mexico.
In 2023, the first U.S. human case was confirmed in a traveler who returned to Maryland from El Salvador. Maryland health officials reported that the person had recovered, and investigators found no evidence of transmission to other people or animals. The USDA has invested millions of dollars to establish facilities for breeding sterile flies as a method to control outbreaks, though these facilities are not yet operational.