USDA officials confirmed a case of the New World screwworm in a calf in South Texas this week [1].
The detection of this flesh-eating parasite threatens the U.S. livestock industry, as the pest can cause devastating tissue damage and death in cattle. Because the parasite has already caused a massive outbreak in Mexico, officials are moving to prevent a wider domestic infestation.
The parasite was detected on Thursday in a single calf [1]. Reports on the exact location of the detection vary, with some sources placing the animal about 25 miles from the U.S.–Mexico border [3] and others citing a distance of about 60 miles [4]. To contain the threat, authorities have established a quarantine zone in the affected region [1].
This is the first time the parasite has appeared in the U.S. in approximately 60 years [5]. The New World screwworm was previously eradicated from the United States six decades ago, making this a significant breach of livestock biosecurity.
The emergence in Texas is linked to an ongoing crisis in Mexico. That outbreak has already affected tens of thousands of cattle [4]. The parasite typically enters the body through open wounds, such as those from branding or injury, where the larvae then feed on the living flesh of the host.
Texas ranchers are now on high alert as the USDA works to monitor the quarantine zone. The goal is to ensure the parasite does not spread further into the interior of the U.S. livestock population, which would result in massive economic losses for the agricultural sector.
“The New World screwworm was eradicated in the United States about 60 years ago”
The reappearance of the New World screwworm after six decades highlights the vulnerability of U.S. agricultural borders to biological threats. Because the parasite is an active crisis in Mexico, the South Texas case suggests that current containment barriers are permeable. If the quarantine fails, the U.S. may face a systemic livestock crisis requiring an expensive, large-scale eradication program similar to the one used 60 years ago.
