A flesh-eating parasite has been confirmed in Texas livestock. Canada has now banned the import of United States livestock, including horses, over the screwworm infestation.

The first case of screwworm was identified in Texas on Wednesday. This marks the first detection of the parasite in the US, roughly 80km (50 miles) from the Mexican border. The outbreak began in Central America in 2023 and has been spreading steadily northward ever since. By late 2025, Mexico had reported thousands of cases in animals and dozens of humans.

Parasite Screwworm Infects Its First American

A second case of screwworm was identified on Friday in the same area. It was this case that prompted Texas rulers to declare a state of disaster over the outbreak. That same day, the Canadian Food Inspection Agency said it would temporarily halt imports of livestock from Texas until further notice and “continue to work closely with US counterparts to assess developments and adjust measures as needed.”

“This pest affects live animals and does not impact inspected Texas beef. Canada’s broad restriction on Texas livestock is an overreaction that is more political than science-based,” the governor told USA Today in a statement.

The parasite, which in its adult form resembles a common housefly, lays its eggs into wounds and natural body openings of warm-blooded animals. The eggs – laid in hundreds by a single fly – hatch into parasitic maggots, which feast for about a week on living flesh, causing an extremely painful and potentially deadly condition. The maggots ultimately burrow out of the bodies of their hosts and dig into soil to pupate, emerging as an adult fly several weeks later to repeat the process. –RT

The screwworm was declared eradicated in the US in 1966, in Mexico in 1991, and all across Central America by the mid-2000s.

Sterile Screwworm Flies Have Been Released To Combat Parasite