FDA Gives Conditional OK for New World Screwworm Treatment

The U.S. Food and Drug Administration announced today that it has conditionally approved fluralaner topical (Exzolt Cattle-CA1) solution for the prevention and treatment of New World screwworm larval infestations in cattle. The product is also indicated for the treatment and control of cattle fever tick in beef cattle over 2 months of age and replacement dairy heifers under 20 months old.

Under FDA’s conditional approval pathway, the agency determined the product is safe and has a reasonable expectation of effectiveness for its intended use. Intervet Inc., based in Rahway, New Jersey, has up to five years to submit additional effectiveness data needed for full approval.

“The FDA is leveraging every resource and authority at its disposal to ensure producers and veterinarians have the critical products they need to protect their livestock and safeguard our food supply against NWS and cattle fever tick,” Timothy Schell, PhD, director of the FDA’s Center for Veterinary Medicine, said in an organizational release. “We remain steadfast in our commitment to ensuring that animal drugs are safe and effective and that food from treated animals is safe to eat.”

According to the FDA, the product met conditional approval eligibility standards because it is intended to prevent and treat a serious or life-threatening illness in cattle, demonstrates effectiveness through complex or difficult studies, and addresses an unmet animal health need. The treatment also received an expedited review through a priority zoonotic animal designation under authority provided in the Coronavirus Aid, Relief, and Economic Security Act.

“This conditional approval gives cattle producers a new tool to combat two parasites threatening the well-being of cattle in the U.S.,” said FDA Commissioner Marty Makary, M.D., M.P.H. “Although NWS has not been detected in the U.S., the cattle fever tick is here. This is the first drug conditionally approved by the FDA specifically for the control and treatment of cattle fever tick.”

Exzolt Cattle-CA1’s labeling includes a 98-day slaughter withdrawal period, intended to prevent unsafe drug residues in meat and protect food safety. The FDA also states the product is not for use in lactating dairy cattle, dairy calves, veal calves, or bulls at least 1 year old intended for breeding.

“This conditional approval gives cattle producers a new tool to combat two parasites threatening the well-being of cattle in the U.S.,” Marty Makary, MD, MPH, FDA Commissioner, said. “Although NWS has not been detected in the U.S., cattle fever tick is here. This is the first drug conditionally approved by the FDA specifically for the control and treatment of cattle fever tick.”

Exzolt Cattle-CA1 is prescription-only and will come in 250 mL, 1 L, and 5 L bottles. It is a single-use, ready-to-use pour-on applied directly to the hair and skin in a narrow strip along the back from between the shoulder blades to the base of the tail.

The conditional approval follows a series of recent FDA actions related to NWS. Lotilaner (Credelio; Elanco Animal Health) received emergency use authorization to treat NWS infestations in dogs, and later, lotilaner chewable tablets (Credelio Cat; Elanco Animal Health) received emergency use authorization for cats and kittens.

“This historic [emergency use authorization] equips veterinarians and cat owners with a treatment solution and provides reassurance that they’re prepared to act quickly if New World screwworm crosses into the US,” Ellen de Brabander, PhD, executive vice president of innovation and regulatory affairs at Elanco, said in a news release.

In cattle, doramectin injection solution (Dectomax-CA1 Injectable; Zoetis) received conditional approval in September 2025 to prevent and treat NWS larval infestations and prevent reinfestation for 21 days.

Separately, Texas Agriculture Commissioner Sid Miller praised the FDA’s decision calling it a landmark for livestock health and a victory for the cattle industry.

“The threat posed to our cattle industry by these dangerous pests is substantial. The New World screwworm can destroy an animal in a matter of days, and the Cattle Fever Tick once brought the Texas cattle industry to its knees,” Commissioner Miller said. “This treatment gives our producers the modern, science-backed tools they need to keep herds safe and will help safeguard everything from small family herds to the nation’s major beef operations.”

Commissioner Miller continued: “President Trump has restored a culture of accountability and action in Washington, D.C. Because of his leadership, federal agencies are responding to agricultural threats quickly and decisively. At the same time, Health and Human Services Secretary Kennedy understands that livestock health is tied directly to food security and national security. His support for timely review and approval of critical tools like Exzolt Cattle is exactly the kind of results-driven action that rural America has been praying for.”