SHERIDAN, WYOMING - December 19, 2025 - Merck Animal Health says the U.S. Food and Drug Administration (FDA) has granted conditional approval for EXZOLT™ CATTLE-CA1 (fluralaner topical solution), positioning the pour-on as a new systemic parasiticide option for U.S. beef operations and replacement dairy heifers facing New World screwworm (Cochliomyia hominivorax) larvae (myiasis) risk and cattle fever tick (Rhipicephalus microplus) pressure.
What the FDA conditional approval covers
According to the company, 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." The product is described as part of the newest class of parasiticides known as isoxazolines, and Merck Animal Health says it is effective for the prevention and treatment of New World screwworm infestations and conditionally approved for the treatment and control of cattle fever tick.
For veterinary practices and producers, this positioning matters because it frames EXZOLT CATTLE-CA1 as both a prevention and intervention tool-two use cases that can influence purchasing decisions, protocol design, and on-farm logistics.
Why New World screwworm is a business risk for cattle operations
Merck Animal Health links the approval to heightened concern about the potential impact on U.S. agriculture and cattle supply chains. "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."
From a B2B perspective, parasite control decisions are rarely just "animal health" choices-they tie directly to labor, herd performance, scheduling, and marketing windows, especially where withdrawal periods and eligibility constraints shape treatment timing.
Conditional approval pathway and what it signals
Merck Animal Health said EXZOLT CATTLE-CA1 was granted conditional approval based on demonstration of safety and a reasonable expectation of effectiveness when administered according to label directions, citing global studies conducted in recent years. "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 notes EXZOLT CATTLE-CA1 is conditionally approved pending a full demonstration of effectiveness under application number 141-617.
Label specifics that will drive adoption planning
Merck Animal Health describes EXZOLT CATTLE-CA1 as a pour-on that delivers fluralaner systemically to act against infestations. The product is approved for use in beef cattle two months of age and older, and in replacement dairy heifers under 20 months. It is not approved for use in bulls intended for breeding (one year of age and older), dairy calves, and veal calves, and the label includes a 98-day meat withdrawal period.
For integrated operations, those parameters can be as important as efficacy claims: they determine where EXZOLT CATTLE-CA1 fits in herd health protocols, how it aligns with production cycles, and what safeguards are needed to maintain compliance.
Commercial rollout and North American relevance
Merck Animal Health said EXZOLT CATTLE-CA1 will be available by prescription in 1 L or 5 L presentations in the first quarter of 2026. The company also emphasized that use is restricted to the labeled indications and that off-label or extra-label use is prohibited by federal law for conditionally approved products. Separately, Merck Animal Health stated it recently received market authorization in Mexico for prevention and treatment of New World screwworm, pointing to cross-border relevance where containment and herd protection strategies can require regional coordination.
For full product information and dosing instructions, visit https://ExzoltCattle-CA1.com.