FDA Conditionally Approves Merck Animal Health’s EXZOLT™ CATTLE-CA1 for the Prevention and Treatment of New World Screwworm (Cochliomyia hominivorax) Larvae (myiasis)

December 4, 2025 12:05 pm EST

EXZOLT™ CATTLE-CA1 is the first in its class and the only product conditionally approved for both the prevention and treatment of New World screwworm and treatment and control of cattle fever tick

RAHWAY, N.J., December 4, 2025 – Merck Animal Health, known as MSD Animal Health outside of the United States and Canada, a division of Merck & Co., Inc., Rahway, N.J., USA (NYSE:MRK), today announced the U.S. Food and Drug Administration (FDA) has granted a conditional approval for EXZOLT™ CATTLE-CA1 (fluralaner topical solution). This innovative product is in the newest class of parasiticides known as isoxazolines. The pour-on solution is effective for the prevention and treatment of infestations caused by New World screwworm (Cochliomyia hominivorax) larvae (myiasis). It is also conditionally approved for the treatment and control of cattle fever tick (Rhipicephalus microplus).

“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.”

EXZOLT CATTLE-CA1 was granted conditional approval based on demonstration of safety and a reasonable expectation of effectiveness when administered according to label directions based on global studies conducted by Merck Animal Health in recent years.

Please refer to Merck website for full information: https://www.merck.com/news/fda-conditionally-approves-merck-animal-healths-exzolt-cattle-ca1-for-the-prevention-and-treatment-of-new-world-screwworm-cochliomyia-hominivorax-larvae-myiasis/