On December 4, the U.S. Food and Drug Administration granted conditional approval to EXXZOLT CATTLE CA1. This is the first isooxazoline pour-on treatment approved for screwworm prevention and treatment in U.S. cattle, and it is the only product with conditional approval for this purpose.
Why This Approval Matters for U.S. Animal Health
This announcement follows renewed national concern about screwworm after a traveler-related case was discovered earlier this year. Although no U.S. livestock were affected, the case demonstrated how quickly pests can spread, highlighting the importance of early detection and response.
Federal agencies swiftly increased surveillance, sterile fly programs, and cross-border monitoring, reminding the industry that vigilance remains crucial, even in a country that has been screwworm-free for decades.
What Conditional Approval Means
Conditional approval allows veterinarians to begin using EXXZOLT CATTLE CA1 while the manufacturer continues collecting additional efficacy data. For producers and veterinarians, this provides:
• A new first-in-class option to prevent and treat screwworm
• Rapid response capability if screwworm were ever reintroduced
• Ease of administration as a long-acting pour-on
• Dual control benefits, including effectiveness against cattle fever ticks
The product is approved only for beef calves under 2 months old and replacement dairy heifers under 20 months, with a 98-day slaughter withdrawal period to ensure meat safety.
Enhancing Biosecurity and Herd Security
Although the United States remains screwworm-free, global travel, changing climate patterns, and wildlife migration create opportunities for occasional introductions. Screwworm infestations can cause severe tissue damage, rapid clinical decline, and significant economic loss if not identified and managed early.
Expanding the toolkit of treatment and prevention options provides veterinarians and producers with a vital advantage in supporting animal health, public health, and U.S. food security.
The Bigger Picture
Screwworm serves as a reminder of how closely connected global movement, biosecurity, and livestock resilience truly are. Outbreaks in other regions have demonstrated how quickly this parasite can spread when detection and treatment tools are limited.
With this new conditional approval, the U.S. cattle industry gains an important layer of protection and a step forward in safeguarding the nation’s herds.
