The U.S. Food and Drug Administration issued an Emergency Use Authorization (EUA) for ivermectin liquid for horses (ivermectin oral solution) for the short-term prevention of New World screwworm (NWS) infestations (myiasis) in horses. The product is authorized for use when administered within 24 hours of the horse’s birth or during initial wound care. Ivermectin liquid for horses is not for use in species other than horses.

“We at USDA have been working with our federal partners to prepare for any potential infestation of animals that may occur as a result of New World screwworm. Today’s announcement is another step in the right direction,” said Brooke L. Rollins, U.S. Department of Agriculture Secretary.

New World screwworm is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. Newborn animals with healing umbilical wounds and animals with open wounds are particularly vulnerable to infestations. This is because NWS flies are attracted to these sites to lay their eggs. Left untreated, infestations can be severe and life-threatening.

For Short-Term Prevention, Not Treatment

Based on the scientific evidence available, the FDA has concluded it is reasonable to believe that ivermectin liquid for horses may be effective in the short-term prevention of NWS myiasis in horses when used as authorized. It has also concluded that the known and potential benefits of the product outweigh its known and potential risks.

“This marks the FDA’s 11th Emergency Use Authorization deployed against New World screwworm,” said Acting FDA Commissioner, Kyle A. Diamantas, J.D. “We will continue to use all available authorities, act with maximum speed and deliver tools to protect animals.”

This EUA authorizes ivermectin liquid for horses only for short-term prevention of NWS myiasis, not treatment. If a wound is already infested, or if an infestation develops after administering ivermectin liquid for horses, contact a veterinarian to discuss treatment options.

“This authorization provides a short-term prevention option for horses, but owners and veterinarians should be aware of the limitations,” said Timothy Schell, Ph.D., director of the FDA’s Center for Veterinary Medicine. “This product’s window of prevention lasts no more than 24 hours. So it is important that the product be used alongside other preventive measures such as bandaging, repellents and other fly-control methods.”

Solution Available by Prescription

Ivermectin liquid for horses is a clear, ready-to-use solution. It can be administered as an oral drench or via a tube going from a horse’s nose to its stomach. This product is available only by prescription from a licensed veterinarian. Do not use this product in species other than horses.

Detailed product information about ivermectin liquid for horses can be found in the Fact Sheet: Emergency Use Authorization of Ivermectin Liquid for Horses (ivermectin oral solution) for New World Screwworm (NWS). This EUA will be effective until it is revoked or the HHS Secretary terminates the declaration that the potential public health emergency presented by NWS justifies the emergency use authorization of animal drugs for NWS.