Canada has imposed an immediate ban on cattle imports from Texas following the confirmation of an outbreak of New World screwworm, a parasitic fly whose larvae feed on living flesh. The decision, announced by the Canadian Food Inspection Agency on Thursday, restricts all live bovine shipments from the southern US state pending further epidemiological investigation.
The outbreak was detected in a herd in Starr County, near the Rio Grande, after ranchers reported unusual lesions and mortality. Laboratory analysis confirmed the presence of Cochliomyia hominivorax, a species eradicated from North America in the 1960s through intensive surveillance and sterile insect release programmes. Its reappearance represents a significant biosecurity failure.
Canada’s move is the first major international restriction triggered by the outbreak. Texas is the largest cattle-producing state in the United States, with an estimated herd of 12 million head. Bilateral trade in bovine animals between Canada and the United States is valued at approximately CAD 1.5 billion annually. The ban will disrupt supply chains across the continent.
The New World screwworm is not native to temperate climates. Its life cycle requires warm, moist conditions. However, climate change is expanding the range of vector-borne pathogens northwards. The UK’s Animal and Plant Health Agency has elevated its risk assessment for screwworm introduction, directing port health authorities to intensify inspections of livestock imports, particularly from the Americas. No cases have been reported in Europe since the 1980s.
The disease causes myiasis: larvae burrow into the tissue of live animals, causing necrosis, secondary infection, and often death if untreated. Human cases are rare but documented. Treatment requires surgical removal of larvae and topical antiparasitics. There is no vaccine.
Texas officials have activated a state-level response: quarantine zones, movement controls, and a public awareness campaign. The US Department of Agriculture is considering a resumption of the sterile fly release programme along the border, which proved effective in the previous eradication effort.
The outbreak underscores vulnerabilities in global agricultural biosecurity. As trade corridors expand and climate pressures intensify, pathogens previously confined to tropical zones are reaching industrialised livestock systems. The UK, which prides itself on high biosecurity standards, must now ensure that its screening protocols are robust enough to intercept pathogens before they establish a foothold.
The situation remains fluid. Canada has not indicated how long the ban will last. We will continue to monitor and report on further developments.
