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Canada imposes temporary ban on Texas livestock
Canada's food inspection agency announced a temporary restriction on cattle and horses entering from Texas after parasitic screwworm larvae were found in two calves this week. The measure applies to animals that spent time in Texas within the past 21 days before crossing the border.
Outbreak details and US response
The U.S. Department of Agriculture (USDA) confirmed a second infected calf in Zavala County on Friday, just days after the first case in 60 years was discovered in La Pryor, roughly 30 miles from the Mexican border. Both calves were under a month old, and the larvae were found in their umbilical areas.
Texas Governor Greg Abbott declared a state of disaster the same day, calling the outbreak an "imminent threat" to the state's agricultural sector. The USDA established a 20-kilometer control zone around the initial detection site, enforcing quarantines, movement restrictions, and heightened surveillance.
Parasite risks and spread
The New World screwworm is a parasitic fly whose females lay eggs in open wounds or mucous membranes of warm-blooded animals, including humans. Once hatched, larvae burrow into living tissue, potentially killing the host if untreated. The parasite thrives in warm, humid climates and has historically spread through Central America and Mexico.
While Canadian officials consider the risk of widespread infestation low due to colder temperatures, they advised farmers to inspect livestock for wounds with discharge or foul odors. Pet owners traveling to Texas were also urged to monitor their animals.
Trade impact and historical context
The U.S. and Canada maintain a robust two-way cattle trade, with 550,000 head imported to Canada in 2025 for slaughter, breeding, and dairy production. The screwworm was declared eradicated in the U.S. in 1966 but has resurfaced sporadically, including a 1970s outbreak.
Long-distance spread typically occurs through human transport, as the flies themselves travel only short distances. The current outbreak marks the first detected in Texas since the parasite began moving northward from Central America and Mexico.
US containment efforts
U.S. officials plan to release hundreds of millions of genetically modified sterile flies to curb population growth, alongside deploying sniffer dogs to detect infected cattle. Some experts, however, question whether these measures will be sufficient to halt the spread.
"This is likely to spread over the course of the summer,"
Texas Governor Greg Abbott, Friday press briefing
Next steps
Canadian authorities will continue monitoring the situation, while U.S. agencies focus on containment within the established control zone. The ban remains in effect until further notice.
