Texas ranchers and livestock owners have a new tool to help prevent New World screwworm infestations, as federal officials authorized a wound spray for use on multiple livestock and wildlife species.
The U.S. Food and Drug Administration issued an Emergency Use Authorization Aug. 7 for CLiK Extra, a dicyclanil topical suspension manufactured by Elanco, for application on or around wounds to prevent New World screwworm infestations. The authorization covers sheep, cattle, goats, swine, camelids such as llamas and alpacas, and several captive and captured wildlife species, including deer, elk, American bison, bighorn sheep and Sonoran pronghorn.
Texas Agriculture Commissioner Sid Miller praised the authorization in an Aug. 7 statement, calling it an important step in protecting livestock and wildlife while stressing that prevention and treatment alone will not eradicate the pest.
“I want to thank President Trump, Health and Human Services Secretary Robert F. Kennedy Jr., the FDA, and everyone at HHS who worked with urgency to make this Emergency Use Authorization a reality,” Miller said.
Miller said the authorization gives ranchers, veterinarians and livestock owners another tool to protect animals and called for continued aggressive eradication efforts.
“But let's not confuse treatment with eradication,” Miller said. “The only proven way to eliminate this pest is to destroy the fly itself through an aggressive program, including the proven SWASS strategy that I've been calling for from day one.”
The FDA said CLiK Extra does not kill New World screwworm larvae. Instead, it acts as an insect growth regulator that disrupts larval development and stops the parasite's life cycle before it can cause tissue damage. The product is authorized for prevention associated with wounds, birth and surgical or husbandry procedures, including dehorning, ear tagging, castration, tail docking and shearing.
The spray is not authorized to treat an existing infestation. If a wound already contains larvae, or an infestation develops after the product is applied, the FDA advises contacting a veterinarian to discuss treatment options.
The product is available over the counter for topical use on or around wounds, but it is not approved or conditionally approved by the FDA for any indication. The emergency authorization allows its use under the conditions specified by the FDA while the federal emergency declaration remains in effect.
The FDA determined, based on the available scientific evidence, that it is reasonable to believe CLiK Extra may be effective in preventing New World screwworm myiasis when used as authorized and that its known and potential benefits outweigh its known and potential risks.
The authorization also carries food-safety restrictions. According to the FDA fact sheet, sheep, cattle, goats, swine, cervids, American bison and bighorn sheep treated with CLiK Extra must not be slaughtered or harvested for human consumption within 86 days of treatment. Treated camelids and Sonoran pronghorn may not be used for human consumption, and the FDA has not established a milk-discard period, meaning the product should not be used on animals producing milk for human consumption.
Acting FDA Commissioner Kyle Diamantas said the authorization gives farmers, ranchers, veterinarians and wildlife managers another tool to prevent the spread of the pest.
Timothy Schell, director of the FDA's Center for Veterinary Medicine, said the authorization's inclusion of wildlife species is intended to protect those animals and reduce their potential role in spreading New World screwworm in the United States.
A growing Texas threat The authorization comes as Texas continues responding to the reappearance of New World screwworm, a parasitic fly that was eradicated from the continental United States in 1966 through the use of the sterile insect technique. The pest's larvae feed on the living tissue of warm-blooded animals and can cause severe wounds, secondary infections and death if left untreated.
The first confirmed Texas case in decades was identified June 3 in a threeweek- old calf in Zavala County. Additional cases subsequently led to the expansion of infested zones across the state. The Texas Animal Health Commission currently lists 15 Texas counties with cases and 32 affected premises.
The threat has moved directly into the Hill Country and Bandera County's surrounding area.
On June 23, New World screwworm was detected in a bovine in neighboring Medina County. The following day, the Texas Animal Health Commission designated portions of Bandera, Medina and Uvalde counties as Infested Zone 09 and imposed animal movement restrictions.
Parts of southern Bandera County remain subject to movement restrictions. TAHC's current guidance states that warm-blooded animals in an infested zone may not be moved outside the zone without prior authorization. Animals leaving an infested zone must be inspected, and a New World screwworm treatment/ movement certificate must accompany the movement.
For Bandera County, the issue is particularly significant because of the county's ranching and equine economy. The restrictions can affect the movement of cattle, horses, sheep, goats, swine and other warm-blooded animals, as well as activities involving livestock exhibitions and other animal events.
TAHC said livestock and pet owners should regularly inspect animals for open wounds and signs of New World screwworm and report suspected infestations. The agency also is working with Texas A&M AgriLife on a certified inspector program to provide animal inspections and issue treatment and movement certificates.
Eradication remains the goal While products such as CLiK Extra can help prevent infestations, state and federal officials continue to emphasize that the longterm goal is eradication of the fly.
Texas is using the sterile insect technique, in which sterilized male flies are released to mate with wild females. Because females mate only once, resulting eggs are not viable, gradually reducing the population over successive generations. TAHC says aerial and ground releases are underway in affected areas.
The federal government also is expanding sterile fly production. The USDA announced Aug. 10 that a new Texas facility intended to produce sterile New World screwworm flies will open in spring 2027, earlier than the previously planned endof- 2027 timeline. The facility is intended to increase U.S. sterile fly production as officials work to push the pest southward.
USDA currently reports that all southern ports of entry remain closed to livestock trade, although the agency has announced a phased reopening beginning with the Douglas, Arizona, port on Aug. 24.
Miller said the new authorization is welcome but should not replace the broader eradication effort.
“I also urge the federal government to fully embrace the aggressive eradication strategy this crisis demands,” Miller said. “Texas producers deserve nothing less than a comprehensive plan that doesn't just slow the screwworm, it defeats it once and for all.”
.png)
