Merck Animal Health has secured a conditional approval from the US Food and Drug Administration for Exzolt Cattle-CA1, a pour-on isoxazoline parasiticide designed to take on some of the most destructive cattle pests threatening US herds. 

 

The topical fluralaner solution is cleared for the prevention and treatment of new world screwworm infestation and conditionally approved for treating and controlling cattle fever ticks—two threats capable of inflicting massive economic damage on the livestock sector.

 

“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 granted the conditional approval after Merck Animal Health demonstrated safety and a reasonable expectation of effectiveness through 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, 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 pour-on delivers fluralaner systemically and is approved for use in beef cattle two months and older, plus replacement dairy heifers under 20 months. It carries a 98-day meat withdrawal period and is not approved for bulls intended for breeding (one year and older), dairy calves, or veal calves.

 

Exzolt Cattle-CA1, authorized under application number 141-617, will be available by prescription in 1-liter and 5-liter bottles starting in the first quarter of 2026. Federal law prohibits any off-label use of conditionally approved drugs. 

 

The US approval follows recent authorization in Mexico, where the product is already cleared to help control and prevent New World screwworm and curb its spread in cattle.