New World screwworm flies — a parasitic pest that poses a major threat to the state’s livestock industry — continue to spread in Southern New Mexico, with the U.S. Department of Agriculture confirming new cases in recent days in Eddy and Sierra counties.
The flies, which burrow into the flesh of warm-blooded creatures and cause painful, sometimes deadly wounds, have likely been spurred on by warm, wet weather in the southern half of the state, said Dr. Samantha Holeck, state veterinarian with the New Mexico Livestock Board.
“Right now, the conditions are just ideal,” Holeck said in an interview.
Common in the Caribbean and Central America, New World screwworm flies were largely eliminated from the U.S. decades ago. They returned to the country in June, with a case identified in a Lea County dog the same month.
The U.S. Department of Agriculture has since identified 124 animal infestations across the Southwest — including 42 in New Mexico. Mexican agriculture officials have reported hundreds more cases in the border states of Sonora, Chihuahua, Coahuila, Nuevo Leon and Tamaulipas.
The weather — including late September floods that resulted in evacuation orders in rural Doña Ana County and decimated chile crops in Hatch — is at least partially to blame for New World screwworm flies’ recent proliferation in the state, Holeck said.
“The more mild fall weather, with the extra rain that we’ve had, it’s created [the] ideal climate for the fly down there in Southern New Mexico, and so I think that’s what’s contributed to the increase in cases, in conjunction with the natural progression of the flies moving up from Mexico,” she said.
What will it take to kill off the flies? While adult flies are more vulnerable to day-to-day temperature swings, it will take a few days of freezing weather to kill off pupae as they develop into flies underground, Holeck said.
Those temperatures aren’t yet in the forecast. The National Weather Service is forecasting a week of pleasant weather in New Mexico, with meteorologists expecting temperatures in the Las Cruces area to hover between 44 and 70 degrees Fahrenheit through Monday.
Agriculture officials for months have been dispersing sterile flies — which can’t produce the larvae that would otherwise pose a threat to livestock — in New Mexico to reduce case counts. So far, Holeck said, authorities have released more than 28 million sterile flies in the state.
The U.S. Department of Agriculture on Tuesday announced plans to start staffing up a sterile fly production facility in Edinburg, Texas. Workers in that facility will raise and sterilize the flies with irradiation prior to dispersal.
“Protecting U.S. livestock and wildlife from New World Screwworm is a national security priority, and this new facility will drastically boost the availability of sterile flies — our most successful offensive capability to drive these serious pests away from our border,” U.S. Agriculture Secretary Brooke Rollins said in a statement Tuesday. “The people filling these vital positions will serve at the front lines in our battle against this serious pest and help ensure that we again eradicate it from our country.”
Margaret O’Hara reports on issues affecting healthy communities in New Mexico. Her work is funded by a grant from Anchorum Health Foundation. Anchorum will not have any role in editorial decisions. The New Mexican and its Public Service Journalism Fund retain full editorial control. Philanthropically funded stories by The New Mexican are made available to all readers without a paywall.
