The US Department of Agriculture has confirmed New World screwworm in American wildlife for the first time. On 21 October its Animal and Plant Health Inspection Service (APHIS) said a hunter-harvested elk from a private game ranch in Pecos County, Texas, had tested positive for the flesh-eating larvae. Because the elk was already dead when it was sampled, the case is classed as inactive.
On the same day New Mexico's state animal health officials confirmed a case in a beef cow in Otero County, one of several detections in the state since the pest crossed from Mexico earlier this year. As of 21 October officials counted seven active US cases and 59 detections in all since the first, a three-week-old calf in Zavala County, Texas, on 3 June. The pace has picked up: three cases were recorded in September and six in the most recent week alone. About 1,000 suspect samples have been submitted nationwide since June, 531 of them from Texas, and a single wild screwworm fly has also been caught in a trap.
Dudley Hoskins, USDA Under Secretary for Marketing and Regulatory Programs, told reporters the wildlife finding and the recent rise do not amount to an outbreak, and credited producers, hunters and state agencies for reporting suspect animals quickly. He said wild fly populations appear low and localised, based on more than 39,000 wildlife observations by APHIS Wildlife Services using trail cameras, drones and feral hog monitoring, and stressed that screwworm is a treatable pest, not a food-safety risk.
The Texas Animal Health Commission is redrawing its infested zones around the new case, while USDA and the Texas Parks and Wildlife Department widen wildlife surveillance in the area. New Mexico has set an infested zone of at least 20 kilometres around its latest detection, inside which animals must be inspected, and treated if needed, before they move. Both states are adding fly traps to find out whether the pest has spread beyond the known zones.
The response relies on the sterile insect technique that eradicated screwworm from the United States decades ago: lab-reared, radiation-sterilised male flies are released so that wild females lay eggs that never hatch. USDA says it had released more than 1.64 billion sterile flies by 22 October. A new production plant at Moore Air Base in Edinburg, Texas, is due to open in April 2027 with 100 million flies a week, and a second phase would add 200 million more; plants in Panama and Metapa, Mexico, are each working towards 100 million a week. USDA's Agricultural Research Service and the Environmental Protection Agency are also field-testing a male-only sterile strain, NovoFly, in Panama. Mexico has recorded more than 29,000 cases since November 2024.
The pest has already reshaped the cattle trade. Washington halted live cattle, horse and bison imports from Mexico for more than a year, which tightened US cattle supplies and has been linked to record beef prices. A phased, port-by-port reopening began in August, and regulators are moving carefully because even a small wildlife reservoir of the pest would complicate a full return to open trade.
Photo: USDA / Wikimedia Commons (Public domain)
Source: Global Agriculture
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