Merck Animal Health SVP: to promote human health, invest in protecting animals

The return of the New World screwworm is reviving concerns about a parasite that once caused extensive damage to cattle herds across the southern United States.

The flesh-eating maggot was eradicated in the United States roughly six decades ago after a major campaign. That effort delivered a significant economic benefit to livestock producers, highlighting the broader business stakes of controlling animal diseases.

A costly threat to cattle producers

New World screwworm had previously decimated cattle herds across the South. The parasite’s impact was severe enough that its eradication became an important achievement for the livestock industry and U.S. agriculture.

According to the source material, the campaign saved livestock producers approximately $6 billion annually, adjusted for inflation. The figure illustrates the financial burden the parasite once placed on producers and the value of preventing its spread.

Earlier outbreaks preceded the latest return

The parasite’s presence did not disappear permanently from the region. Brief outbreaks were recorded in Texas during the 1970s and in the Florida Keys in 2016.

Its return now places renewed attention on animal health risks that can affect livestock production. The available information does not specify the location or scale of the latest development, but the parasite’s history shows why its reappearance matters to cattle producers.

Why the development matters

The New World screwworm episode demonstrates how animal-health threats can carry substantial economic consequences. Past eradication efforts protected herds and saved producers billions of dollars each year. The parasite’s return underscores the continuing importance of protecting livestock from diseases and infestations that can disrupt agricultural businesses.