Merck Animal Health Receives FDA Conditional Approval for Exzolt Cattle-CA1 to Combat New World Screwworm

Merck Animal Health, a division of Merck & Co., received conditional approval from the U.S. Food and Drug Administration for Exzolt Cattle-CA1 fluralaner topical solution, the first novel ectoparasiticide introduced for beef cattle in several decades, for the prevention and treatment of infestations caused by New World screwworm (NWS) larvae, or myiasis. The company reaffirmed its commitment to supporting the cattle industry’s response to the growing threat of NWS during a symposium in San Antonio, underscoring the continued need for industrywide collaboration to combat this devastating parasite.

Exzolt Cattle-CA1 is a pour-on product that delivers the active ingredient fluralaner systemically. It is the first and only topical product conditionally approved for NWS prevention and treatment and brings a new active ingredient and drug class to the cattle industry, with no known resistance. The product is approved for use in beef cattle 2 months of age and older and in replacement dairy heifers younger than 20 months, and is also conditionally approved for the treatment and control of cattle fever tick. It has been available in the United States since early spring 2026, with distribution focused on southern border states to help ensure access in regions at the highest risk of NWS outbreak. Exzolt Cattle-CA1 is available by prescription in 1- and 5-liter presentations.

The San Antonio symposium brought together cattle producers and veterinarians from high-risk regions. Leading researchers, academic experts, government representatives and Merck Animal Health technical team members delivered programming focused on NWS preparedness, risk mitigation and coordinated strategies to help protect U.S. livestock. “The U.S. cattle industry successfully eradicated New World screwworm in the past, and renewed vigilance and collaboration across the industry are essential to preventing and managing this evolving threat,” said the president of Merck Animal Health. “Merck Animal Health is committed to being a partner in that effort by providing innovative solutions to support veterinarian and producer preparedness.”

Experts at the symposium stressed the importance of coordinated, industrywide efforts to curb the spread and minimize risk, noting that NWS affects all warm-blooded animals. Key prevention strategies highlighted by industry leaders include daily observation of livestock and wildlife to detect wounds and potential infestations early, prompt reporting of suspected cases to enable rapid response, and a strong veterinarian relationship to support development of an NWS management plan.

“Innovation plays a critical role in how we respond to emerging threats like New World screwworm,” said the executive director of livestock technical services for Merck Animal Health. “Exzolt Cattle-CA1 represents an entirely new drug class never before used in U.S. cattle. When paired with strong veterinary partnerships and proactive management, it gives the industry an important new tool to help protect cattle herds.”