Texas Agriculture Commissioner Sid Miller is thanking the U.S. Food and Drug Administration (FDA) and the U.S. Department of Health and Human Services (HHS) for giving emergency approval to a topical wound spray called CLiK Extra. The spray can help prevent screwworm infestations in cattle, sheep, and other livestock. It can also be used on some wildlife, including deer, elk, bighorn sheep and American bison.
CLiK Extra does not kill screwworm larvae. Instead, it disrupts their development, keeping them from completing their life cycle. It is intended to prevent infestations around wounds — including injuries, wounds from giving birth, and those caused by procedures such as dehorning and castration. The F-D-A says CLiK Extra is not approved for any specific use, but determined its potential benefits outweigh the risks during the emergency authorization.
But as Texas Public Radio reports, Miller is expressing his frustration with the U.S. Department of Agriculture (USDA). He says the federal agency has relied on an approach that hasn’t been more effective. “Sterile flies are very ineffective. They haven’t worked. We’ve been releasing 100-million a week for 19 months. That’s two billion sterile flies, yet we have more active screwworm cases today than the day we started. That’s insanity.”
Miller says estimates predict that releasing 500-to-700 million flies would prevent about 2,000 cases of New World Screwworm. He tried to convince USDA officials to deploy what’s known as the Screwworm Adult Suppression System (SWASS), a proven USDA-developed program that uses targeted bait to kill fertile adult screwworm flies before they can reproduce. He did so when the pests were first detected in southern Mexico, in hopes of keeping screwworms from reaching the U.S. border. “I did share that scientific information with my Mexican counterpart. They were elated. They had been trying to develop a fly bait. This fly bait kills 80-90% of the flies.”
Miller says fly bait would be much more efficient than the expansion of the sterile fly program, or more likely, as at least another component in the fight against screwworm.
But critics say SWASS relies on dichlorvos, an insecticide classified by the Environmental Protection Agency (EPA) as a probable human carcinogen. And they also noted that no products are currently registered for that use.
But in a June 8 statement Miller said, “It is important to note that neither I, nor the Texas Department of Agriculture, have advocated for the use of Dichlorvos in SWASS. While that insecticide worked well to eradicate the New World Screwworm from Texas in the 1970s, it has since been determined to be a carcinogen,” insisted Miller.
He concluded, “Nevertheless, there are alternative insecticides available for SWASS which have been determined can be used to safely combat the screwworm as part as SWASS strategy.”
In fact, according to the National Institutes of Health, research and agricultural evaluations have identified alternatives like trichlorfon as a viable, longer-lasting, and mammal-safe alternative for SWASS pellets, alongside other approved premise and topical treatments like permethrin, coumaphos, and cypermethrin.
But, USDA undersecretary for research education and economics, Scott Hutchins, has recently stated that scientists are aggressively working to discover specific scents that attract female screwworm flies. In this way, he contends, it would create a more “modern SWASS” system in the future, without any potential collateral impact to the environment.
And the bottom line, according to the push back from the USDA: the currently used, older bait technology of SWASS simply raises concerns over safety and effectiveness.
Finally, Miller's time as Texas Agriculture Commissioner ends in January, leaving him with a little more than three and a half months in office. His attempts at a fourth term were thwarted by a GOP primary loss to Nate Sheets on March 3. This push by Miller, then, for the reintroduction of SWASS, may have as much to do with the legacy of this eighth generation Texas farmer and rancher, as it does about governmental policy to help eradicate a flesh-eating parasite.
