A parasitic invader from the tropics has breached a border once thought secure. Canada has imposed an immediate ban on the import of cattle from Texas following an outbreak of New World screwworm (Cochliomyia hominivorax), a flesh-eating maggot capable of decimating livestock populations. The decision, announced by the Canadian Food Inspection Agency late Tuesday, marks the first such restriction in decades and underscores the creeping biological toll of a warming planet.
Screwworm myiasis is not a disease of neglect. It is a predator that exploits wounds, however small. A single gravid female can lay up to 400 eggs in a scratch, a tick bite, or a navel of a newborn calf. Within hours, larvae hatch and begin burrowing into living tissue, consuming the host from the inside out. The result is a gruesome, often fatal infection that can spread through a herd with devastating speed.
The outbreak in Texas was confirmed last week near the Mexican border, where the pest has long been endemic. Screwworms were eradicated from the United States in 1966 using the sterile insect technique, a triumph of entomological engineering. But climate change is redrawing the map. Rising temperatures have allowed the screwworm to creep northward, surviving winters that once limited its range. The current outbreak is a harbinger of a larger biospheric shift: pathogens and parasites are moving poleward as the world warms.
Canada’s ban is a calibrated response. The country imports roughly 600,000 head of cattle annually from the United States, a significant portion from Texas. The economic cost of the ban will ripple through the supply chain, but the alternative is unthinkable. An established screwworm population in Canada would be catastrophic. The cold is no longer a reliable barrier.
“This is not an overreaction,” said Dr. Helena Vance, Science and Climate Correspondent. “The screwworm is a biological machine. It doesn’t need a passport. It needs a wound and 30 degrees Celsius. We are giving it both.”
The outbreak also exposes the fragility of our agricultural defences. The sterile insect technique, effective for decades, requires constant funding and vigilance. Budget cuts and complacency have weakened the buffer. The United States Department of Agriculture has already deployed emergency teams to Texas, but eradication will take months, if not years.
For Canada, the ban is a stopgap. The real solution lies in robust climate adaptation: better surveillance, rapid response protocols, and a recognition that the old boundaries are dissolving. The screwworm is a message from a changing planet. We ignore it at our peril.
As Dr. Vance noted, “The invasion is not coming. It is here. We are now in the era of biological displacement.”
