Canada's food inspection agency has announced a temporary ban on livestock from Texas following the discovery of flesh-eating screwworms in calves. The ban applies to cows and horses that were in Texas within 21 days prior to attempting to cross into Canada, according to an agency news release. This decision follows the U.S. Department of Agriculture's (USDA) report of the parasite being found in a second calf in Texas, prompting Texas Governor Greg Abbott to declare a state of disaster due to the outbreak's potential threat.
The New World Screwworm is a parasitic fly that lays eggs in open wounds of warm-blooded animals. If untreated, the larvae can burrow through the flesh and kill the host. The first case in Texas was detected in a three-week-old calf in La Pryor, near the Mexico border, and a second case was found in a one-month-old calf in Zavala County.
In response to the outbreak, the USDA has established a 20-kilometer-wide control zone and implemented quarantines and movement controls. Although Canadian officials believe the colder climate will prevent the parasite from becoming a problem in Canada, they have advised farmers to monitor livestock for wounds and to check pets that may have traveled to Texas.
The U.S. and Canada engage in a two-way cattle trade, with livestock moving across the border for various purposes. The number of cattle imports from the U.S. has increased, with 550,000 cattle imported in 2025. The screwworm was previously considered eradicated in the U.S. in 1966, but there have been sporadic cases since, including an outbreak in the 1970s. To combat the current outbreak, U.S. officials plan to release genetically altered sterile flies and use sniffer dogs to detect the parasite in cattle.
