Merck’s New Animal Health’s Isoxazoline Parasiticide EXZOLT CATTLE-CA1 For Screwworm And Tick Control Set For U.S. Launch Following FDA Conditional Clearance

Merck Animal Health, a division of Merck & Co., Inc., announced that the U.S. FDA has granted conditional approval for EXZOLT™ CATTLE-CA1, a new fluralaner-based topical solution formulated for cattle. The parasiticide belongs to the isoxazoline class and is designed to prevent and treat infestations caused by New World screwworm larvae. It also holds conditional approval for the treatment and control of cattle fever ticks, addressing two significant external parasite threats in livestock.

“The threat of New World screwworm represents a growing concern to U.S. agriculture, potentially causing devastating economic losses for cattle producers that could reach hundreds of millions of dollars,” said Rick DeLuca, president, Merck Animal Health. “EXZOLT CATTLE-CA1 is the first novel ectoparasiticide introduced for beef cattle in several decades, and its conditional approval reflects our commitment to bringing new, innovative solutions to market that address resistance concerns. We worked closely with the FDA to accelerate availability so that veterinarians and cattle producers will have access to a powerful new tool to protect cattle from these serious parasites, helping to safeguard the industry’s economic future and the nation’s beef supply.”

The FDA’s conditional approval is based on demonstrated safety and a reasonable expectation of effectiveness supported by global studies conducted by Merck Animal Health. The pour-on formulation delivers fluralaner systemically and is approved for use in beef cattle aged two months and older, as well as replacement dairy heifers under 20 months. It carries a 98-day meat withdrawal period and is not approved for bulls intended for breeding, dairy calves, or veal calves.

EXZOLT CATTLE-CA1 will be available by prescription in 1-liter and 5-liter packaging beginning in the first quarter of 2026. As a conditionally approved product, its use is legally restricted to labeled indications, prohibiting any off-label applications. The product remains under application number 141-617 as Merck continues generating data to support full approval.

“Merck Animal Health has a proud legacy of innovation, providing science-based solutions and supporting producers in adopting sustainable parasite management programs including resistance control,” said Holger Lehmann, D.V.M., Ph.D., vice president, pharmaceutical research & development, Merck Animal Health. “We are pleased that the FDA previously established an accelerated regulatory pathway for novel treatments that address life-threatening diseases through expanded conditional approval and priority zoonotic animal drug designation. Without this regulatory route, the registration of EXZOLT CATTLE-CA1 would not have been possible in such a short time.”

The company also noted that EXZOLT CATTLE-CA1 recently received market authorization in Mexico for preventing and treating New World screwworm. This expansion is expected to support broader parasite control efforts and help protect cattle health across the region.