Last week, the United States halted all cattle trade with Mexico to stop the spread of a parasitic flesh-eating fly known as the New World screwworm. According US Department of Agriculture (USDA) Secretary Brook Rollins, the deadly parasite poses a national security risk that could impact the nation's food supply. But the outbreak could also harm big game herds if it spreads into the United States, conservationists warn.
“The health and sustainability of North America’s deer populations are paramount to our mission,” said Nick Pinizzotto, President and CEO of the National Deer Association (NDA), in a prepared statement. “The re-emergence of the New World screwworm poses a significant threat not only to livestock but also to our nation’s wildlife, especially deer."
According to NDA, New World screwworms have killed enough deer during previous outbreaks "to suppress deer population growth in many regions, especially Florida and Texas." Scientists have tamped down previous outbreaks by breeding and releasing sterile male flies, thereby suppressing breeding populations, NDA added. But a more recent outbreak in 2016 still managed to kill 132 endangered Key deer in Florida.
Rollins announced the livestock closure on Tuesday, May 11, and by May 14, a bi-partisan group of Texas lawmakers had already introduced a bill that would authorize and fund the construction of a new sterile fly production facility. Both NDA and the Wild Sheep Foundation (WSF) endorsed the bi-partisan bill shortly after it was introduced last week.
“As a life-long resident of Texas, this one hit home for me,” said Corey Mason, the Wild Sheep Foundation's VP of Conservation & COO. “I recall the horror stories from the last outbreak back in the 1960s and with our recent efforts to re-establish desert bighorn sheep in Texas, not to mention what this means for cattle, mule deer and whitetail deer, this situation must be dealt with swiftly.”
Texas' desert bighorn are already reeling from disease and die-offs caused by invasive aoudad, also known as Barbary sheep, WSF noted in a recent press release. "A New World screwworm infestation would have catastrophic effects on the remaining population," added Sam Cunningham, WSF Director and President of Texas Bighorn Society, "potentially extirpating the species entirely."
The USDA says screwworms cause deadly damage to their hosts when they burrow into an open wound. In addition to livestock and big game, they can impact birds and even humans on rare occasions.
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The recent screwworm outbreak in Mexico has spread to remote farms as far north as Oaxaca and Veracruz—about 700 miles from the U.S. border. Due to this "unacceptable northward advancement," the USDA says, "additional action must be taken to slow the northern progression of this deadly parasitic fly." Both NDA and WSF say sterile male flies are the key to stopping the outbreak as they can "effectively wipe out an entire generation of screwworms in a given area."
