The U.S. Food and Drug Administration has issued an Emergency Use Authorization for generic Nitenpyram Tablets to treat New World screwworm infestations in certain dogs and cats, marking the first generic animal drug authorized for use against the parasite.
The authorization comes days after federal officials confirmed the first U.S. detection of New World screwworm in decades. On June 3, the U.S. Department of Agriculture identified larvae in a 3-week-old calf in Zavala County, Texas, prompting containment measures, including a quarantine zone, sterile insect releases, and intensified surveillance efforts, as reported by The Dallas Express.
Days later, a veterinarian in Andrews County, Texas, submitted samples from a dog believed to be infested with NWS. The dog had reportedly been in Mexico recently. Although originally reported as a Texas case, it was later reclassified as a New Mexico case after it was determined that the dog resides in Lea County, which is across state lines.
Federal officials said the over-the-counter treatment is intended for dogs, puppies, cats, and kittens that weigh at least two pounds and are at least four weeks old.
“The U.S. government is moving aggressively to contain and eliminate New World screwworm,” U.S. Health and Human Services Secretary Robert F. Kennedy Jr. said in a news release. “Today’s authorization is the latest HHS action to strengthen our response. It puts an affordable, fast-acting treatment in the hands of pet owners, strengthens our containment strategy, and helps stop this destructive parasite from spreading further in the United States.”
According to the FDA, available scientific evidence indicates it is reasonable to believe Nitenpyram Tablets may be effective in treating New World screwworm myiasis in eligible pets and that the benefits outweigh potential risks.
“The FDA has spent nearly a year fast-tracking reviews and readying for the arrival of New World screwworm in the U.S.,” Acting FDA Commissioner Kyle Diamantas said. “As of today, under the Trump administration’s decisive leadership, the FDA has issued ten EUAs and three conditional approvals for drugs to combat this threat, and this count will continue to grow as we receive more animal drug submissions and unleash American regulatory speed.”
New World screwworm flies lay eggs in open wounds or the mucous membranes of mammals. After hatching, the larvae burrow into living tissue and feed on flesh. The pest can affect livestock, wildlife, pets, and, in rare cases, humans.
Federal officials said Nitenpyram works quickly, killing most larvae within hours of the first dose. A second dose should be administered six hours later. Because the medication is short-acting, it does not prevent future infestations.
Following treatment, veterinarians may need to remove remaining live or dead larvae and provide wound care. Pet owners are encouraged to consult a veterinarian regarding treatment and ways to reduce the risk of reinfestation.
“The Trump Administration is taking a whole-of-government approach to fighting New World screwworm. USDA has been working with our partners to prepare for this day and were ready day one to spring into action,” U.S. Department of Agriculture Secretary Brooke Rollins said. “HHS and FDA have been great partners in this fight, and I am thankful to Secretary Kennedy for making sure cat and dog owners have access to treatment should they need it.”
The FDA said the authorization also expands available treatment options during the response effort.
“Generic animal drugs build resilience in our domestic supply chain and play a critical role in expanding the toolkit of U.S. veterinary drugs for New World screwworm,” said Timothy Schell, director of the FDA’s Center for Veterinary Medicine. “By authorizing this generic treatment, FDA is reinforcing our commitment to providing timely, affordable options to safeguard animal health for American pet owners.”
Meanwhile, Texas and federal officials continue efforts to contain the recently detected infestation in South Texas. The Texas Animal Health Commission established an infested zone covering parts of Zavala and Uvalde counties, with movement restrictions in place for warm-blooded animals. A 20-kilometer buffer zone surrounds the detection site.
So far, there have been seven confirmed NWS cases in the U.S.: six involving calves and goats in Texas, and the dog from Lea County, New Mexico.
Response efforts include fly trapping, surveillance, sterile male fly releases, and movement controls. Officials have emphasized that rapid containment is critical for Texas, which leads the nation in cattle production with an industry valued at $15.5 billion as of 2022.
Nitenpyram Tablets are available without a prescription in 11.4-milligram and 57-milligram strengths, with dosage determined by an animal’s weight. The product is sponsored by Felix Pharmaceuticals Pvt. Ltd., based in Ireland.
Livestock owners and pet owners are urged to inspect their animals for wounds and report any suspicious larvae infestations immediately.
