The US Department of Agriculture announced Wednesday that the New World screwworm, a flesh-eating parasite that infects cattle and other warm-blooded animals, has been detected in a calf in Texas. The pest was previously declared eradicated in the United States in 1966.

Experts believe the screwworm migrated from Central America through Mexico into Texas, bypassing biological barriers that had contained it for decades. Between mid-July and mid-August 2025, Mexico reported a 53% increase in animal cases. Humans can also be infected, though rarely.

Female screwworm flies lay eggs in wounds of warm-blooded animals; the larvae hatch and feed on living tissue for about a week before dropping to the ground to pupate. Newborn calves are especially vulnerable due to umbilical wounds. Infestations cause painful, progressive wounds with visible maggots and can be fatal if untreated.

The current case involves a three-week-old calf in LaPryor, Texas, about 50 km from the Mexican border. A 20-km quarantine zone has been established, banning animal movement. Cheryl Whitehorn of the London School of Hygiene and Tropical Medicine stated that key measures include vigilance, case isolation, larval elimination, and sterile male release programs.

The US typically imports over one million Mexican cattle annually but halted imports last year due to the parasite's spread, contributing to rising beef prices. A US outbreak could cost the Texas economy $1.8 billion in losses. Most ranchers lack experience in diagnosing and treating screwworm after decades of eradication, experts warn.

Source: www.aljazeera.com