WASHINGTON, D.C. — The Food and Drug Administration authorized prescription ivermectin for the short-term prevention of New World screwworm infestations in horses, expanding federal preparations against a parasite capable of threatening livestock and agricultural production.
The emergency authorization covers Ivermectin Liquid for Horses, an oral solution that may be administered within 24 hours of birth or during initial wound care. It applies only to horses and does not authorize the drug for other animal species.
The FDA concluded that available scientific evidence provides a reasonable basis to believe the product may prevent New World screwworm myiasis when used under the authorization. The agency also determined that the expected benefits outweigh the known and potential risks.
The authorization covers prevention, not treatment. Horse owners must contact a veterinarian if an existing wound is already infested or if an infestation develops after the drug is administered.
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 injuries face elevated risk because the flies lay eggs at those sites.
Untreated infestations can cause severe injury and death.
The product’s preventive effect lasts no longer than 24 hours, according to the FDA. The agency advised owners and veterinarians to combine it with bandaging, repellents and other fly-control measures.
“This authorization provides a short-term prevention option for horses, but owners and veterinarians should be aware of the limitations,” Timothy Schell, director of the FDA’s Center for Veterinary Medicine, stated.
The ready-to-use solution may be administered as an oral drench or through a tube inserted through a horse’s nose into its stomach. It will be available only through a licensed veterinarian’s prescription.
Acting FDA Commissioner Kyle Diamantas identified the action as the agency’s 11th emergency use authorization involving New World screwworm.
Federal agriculture and health agencies have been preparing for possible infestations as the parasite poses risks to livestock, wildlife and companion animals.
The authorization will remain effective until the FDA revokes it or the Department of Health and Human Services ends the emergency declaration supporting the use of animal drugs against New World screwworm.
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