U.S. agricultural authorities confirmed the detection of the New World screwworm in Texas this week, marking the first time the parasite has appeared in the U.S. in 60 years [1], [2].
The return of the parasitic fly poses a severe threat to the nation's livestock industry, pets, and wildlife. If left unchecked, the parasite can cause fatal myiasis in cattle, potentially leading to widespread animal death and significant economic losses for ranchers.
Officials from the U.S. Department of Agriculture (USDA) and the Animal and Plant Health Inspection Service (APHIS) identified the infestation in La Pryor, located in Zavala County, Texas [4]. The specific case involved a three-week-old calf [3].
Because the parasite feeds on the living flesh of warm-blooded animals, it is often described as a flesh-eating parasite. The USDA has initiated an emergency containment response to prevent the fly from spreading beyond the affected area in Texas. This response includes increased surveillance and coordination with local ranchers to identify and treat any other infected animals.
While the confirmed case is isolated to Texas, other states have been notified to remain vigilant. Colorado has been placed on alert, though no cases have been reported there to date [5].
The New World screwworm is known for its ability to enter open wounds, including those from injuries or childbirth, where it lays eggs. The resulting larvae burrow into the animal's tissue, causing extensive damage and systemic infection. The absence of the parasite for six decades had previously allowed the U.S. agricultural sector to operate without the need for intensive screwworm eradication programs.
“The New World screwworm has returned to the US for the first time in 60 years.”
The reappearance of the New World screwworm threatens the biological security of the U.S. livestock industry. Because the parasite can devastate cattle populations and spread rapidly through wildlife, the USDA must successfully contain the Texas outbreak to avoid a nationwide eradication effort that would cost millions of dollars and disrupt meat production.
