Merck Animal Health, a division of Merck & Co., underscores the continued need for industrywide collaboration to combat the growing threat of New World screwworm following confirmation of the first case in US cattle.

As part of its response, Merck Animal Health recently hosted a New World screwworm symposium in San Antonio. Held April 22-24, the event 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 US livestock.

“The US 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 Rick DeLuca, 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.”

During the symposium, experts stressed the importance of coordinated, industrywide efforts to curb the spread and minimize risk. Because NWS affects all warm-blooded animals, preparedness and strong collaboration across stakeholders are critical. 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
• A strong veterinarian relationship to support development of an NWS management plan 

In December 2025, Merck Animal Health received conditional approval from the US Food and Drug Administration for Exzlot Cattle-CA1 (fluralaner topical solution), the first novel ectoparasiticide introduced for beef cattle in several decades. Exzolt Cattle-CA1 is a pour-on product for the prevention and treatment of infestations caused by New World screwworm larvae (myiasis). The product 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.

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

Exzolt Cattle-CA1 brings a new active ingredient and drug class to the cattle industry, with no known resistance. It is the first and only topical product conditionally approved for NWS prevention and treatment and delivers the active ingredient fluralaner systemically against infestations. Exzolt Cattle-CA1 is approved for use in beef cattle 2 months of age and older and in replacement dairy heifers younger than 20 months. It is also conditionally approved for the treatment and control of cattle fever tick.

Exzolt Cattle-CA1 is available by prescription in 1-liter and 5-liter presentations.

Source: Merck Animal Health