FDA expands emergency ivermectin access as New World screwworm spreads in US cattle

United States: The FDA broadens emergency use of ivermectin-based controls amid escalating screwworm outbreaks in cattle, highlighting regulatory shifts and mounting pressures on livestock amid rising domestic cases, especially in Texas.

The US Food and Drug Administration has widened emergency access to ivermectin-based controls as New World screwworm spreads in cattle. The move gives producers another tool, but also underlines how far the outbreak has already pushed regulators beyond normal approval channels.

According to the FDA, Bimectin, a generic injectable ivermectin, can be used within 24 hours of birth, at castration or when a wound appears. The agency said the over-the-counter product is barred from lactating dairy cows and veal calves, and carries a 35-day slaughter withdrawal period.

Bimectin is a generic version of Ivomec, which won emergency authorisation in February. The FDA has now issued 15 emergency use authorisations and three conditional approvals for animal drugs against the parasite, according to its animal-health updates dated September 3, 2026.

The agency said it relied on existing bioequivalence evidence and earlier ivermectin studies rather than fresh trials. It has also authorised products for horses, dairy cattle and multiple other species, reflecting the pressure on livestock systems as domestic cases continue to rise, with Texas among the areas most affected.