Follow-Up: FDA Issues Emergency Use Authorization for Bravecto to Treat New World Screwworm in Dogs and Puppies
The U.S. Food and Drug Administration (FDA) announced on November 3 that it has issued an emergency use authorization (EUA) for Bravecto tablets, made by Intervet, a unit of Merck Animal Health, to treat New World screwworm infestations in dogs and puppies. The FDA said that, based on the available scientific evidence, it is reasonable to believe the drug may be effective in treating screwworm infestations and that its potential benefits outweigh its risks when used as authorized.
Bravecto's active ingredient is fluralaner, which was already approved for flea- and tick-related uses in dogs and puppies. The FDA noted that fluralaner belongs to the isoxazoline class of antiparasitic medicines, which has been associated with neurologic adverse reactions including muscle tremors, loss of coordination and seizures. The authorized tablets are available only by prescription through a licensed veterinarian. The FDA also said most dogs in the United States remain at low risk, as confirmed cases are limited to a restricted geographic area.
The New World screwworm, Cochliomyia hominivorax, is a parasitic fly whose larvae burrow into the open wounds and mucous membranes of warm-blooded animals and feed on living tissue. It can infest livestock, pets and wildlife, occasionally birds, and in rare cases people, and the damage is often deadly to the animal. On August 18, 2025, the Secretary of Health and Human Services declared that the screwworm presents a significant potential for a public health emergency, allowing the FDA to use the emergency authorization pathway for animal drugs. As of November 3, the FDA has issued 16 emergency use authorizations and three conditional approvals for screwworm drugs, and its Center for Veterinary Medicine is working with the U.S. Department of Agriculture (USDA), the Environmental Protection Agency (EPA) and state animal health officials on the response.
GSM has been following the screwworm's northward spread: the USDA is spearheading the national response and is building a $750 million sterile-fly facility in Edinburg, Texas; in late October, Arizona confirmed its first case, in a dog whose wound was found to carry larvae, and quarantine zones in New Mexico and Texas have been adjusted repeatedly since. The authorization of a widely used dog antiparasitic gives front-line veterinarians a ready treatment option for pets.
(Source: U.S. Food and Drug Administration)
Source: U.S. Food and Drug Administration
Published by GSM · USA (original Chinese edition)
Photo: 图：美国食品药品监管局（FDA）位于马里兰州 Silver Spring 的 White Oak 园区总部大楼（GSM 四级固定图库）。 / Photo: U.S. Food and Drug Administration headquarters at the White Oak campus in Silver Spring, Maryland (GSM fixed asset library).
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