New Mexico health and agriculture officials are urging caution now that the New World screwworm fly — a sometimes-deadly pest that poses a major threat to the livestock industry — has returned to the U.S. for the first time in decades.
There haven’t been any confirmed screwworm infestations in New Mexico, and it remains tough to predict whether the flies will make their way into the state, said Dr. Samantha Holeck, state veterinarian with the New Mexico Livestock Board.
“It’s too early to tell, but it’s never too early to make people aware of the concern and what to look for,” she said.
Common in the Caribbean and Central America, screwworm flies’ larvae burrow into the flesh of warm-blooded creatures — including livestock, pets, wildlife and, in rare cases, people — and feast upon healthy tissue, causing painful and putrid wounds.
Screwworm flies made their official return to the United States on Wednesday, after being eliminated from the country since the 1960s. The U.S. Department of Agriculture Animal and Plant Health Inspection Service confirmed the screwworm infestation in the umbilical area of a 3-week-old calf in La Pryor, Texas — about 100 miles west of San Antonio.
U.S. Rep. Gabe Vasquez voiced his concerns about the screwworm infestation to U.S. Agriculture Secretary Brooke Rollins during a House Agriculture Committee meeting Tuesday.
“That could devastate our cattle industry and should be — and must be — contained and dealt with immediately,” Vasquez said.
Precautions
The flies’ return to the U.S. comes after months of monitoring by state and federal health and agriculture authorities. The U.S. Agriculture Department has reported for months infestations moving northward, from Central America to the Mexican border states of Tamaulipas and Nuevo León and finally to Texas.
In response to that movement, the Agriculture Department has ramped up efforts to breed and disperse sterile screwworm flies, which can’t produce the larvae that would pose a threat to warm-blooded critters.
The U.S. Food and Drug Administration, meanwhile, has issued emergency use authorizations for medications to prevent and treat screwworm infestations in cattle, sheep, goats, horses, birds, dogs and cats.
All southern ports of entry have been closed to livestock trade since July. That means the hundreds of thousands of cattle that would typically enter the U.S. from Mexico at Santa Teresa each year are no longer coming into the country.
“If we all work together and follow … the movement restriction guidance, there is no reason to believe that this incursion will result in any sort of establishment of the pest on our side of the border,” Rollins said Thursday during a call with reporters.
Rollins noted the nation’s food supply is not at risk, and screwworm infestations aren’t the result of any disease or virus.
“This is not a food safety issue; this is a food production issue,” Texas State Veterinarian Lewis “Bud” Dinges said during the media call. “New World screwworms do not infest meat, fruits, vegetables or other food sources.”
New Mexico impacts
The spread of screwworm to the U.S. will increase agricultural and health officials’ vigilance of animal movement inside the country, said Holeck.
“While it was still contained in Mexico and the ports were closed, we didn’t have to really worry about any sort of legal movement of livestock,” she said.
Like New Mexico and the federal government, Texas has spent years preparing for the possibility of screwworm infestations and has imposed strict limits on animal movement in South Texas — including a quarantine on all warm-blooded animals, Dinges said.
New Mexico is relying on those precautions, Holeck said: “We’re counting on the enforcement of those restrictions to help keep them contained as long as possible.”
Holeck encouraged New Mexico ranchers to keep a close eye on their livestock and respond quickly to any unusual wounds.
Traveling with pets to places with screwworm fly infestations poses a big risk, too, because agriculture authorities don’t have as much control over small animal movements, Holeck added. Pet owners should consider southern Texas a “high-risk area” for infestations, pay close attention to their pets and talk to their veterinarians about preventive treatments.
“Being diligent is the best thing right now,” she said.
While livestock, wildlife and pets are most at risk for infestation, people can be affected, too, said Dr. Erin Phipps, public health veterinarian at the New Mexico Health Department.
Thousands of human infections have occurred in recent years in Mexico and Central America, where the flies regularly circulate, but human cases represent just a tiny fraction of total infestations.
“Right now, awareness is key,” Phipps said. “We do not have New World screwworm in New Mexico at this point, so there’s no specific actions to take for residents.”
Still, Phipps recommended taking precautions — like wearing long sleeves and long pants, covering any open wounds and keeping a close eye on pets — if you’re planning to visit an area where screwworm flies may be.
“The largest concern is for our livestock industry, wildlife, animals. But humans can be affected as well, and right now, we encourage awareness for people to protect themselves and their animals,” Phipps said.
