New World Screwworm returns to US after 60 years, Texas case confirmed

The US officials have issued an unsettling warning against the rare and deadly flesh-eating parasite “New World Screwworm” which appeared in the United States after 60 years.

New World Screwworm, Cochliomyia hominivorax, is a deadly parasite which feeds on warm-blooded animals and the first case has been confirmed in a three-week-old calf in La Pryor, Texas, located roughly 30 miles from the US-Mexico border.

Taking to social media on Wednesday, the US Secretary of Agriculture Brooke Rollins confirmed the presence of New World screwworm fly, citing, “As expected, USDA_APHIS confirmed the detection of a New World Screwworm (NWS) fly in a 3 week old bovine in Zavala County, Texas. USDA and Texas Animal Health officials are taking immediate action to contain and eradicate NWS from the area.”

The detection of the screwworms in the United States is not a good sign as they were largely eradicated in America in the 1960s.

While the USDA has mobilized personnel to support the effort, Texas Agriculture Commissioner Sid Miller has criticized the federal response, arguing that it was too slow and reliant on a single, long-term strategy.

NWS flies lay eggs in open wounds or mucous membranes. Upon hatching, the larvae feed on the host’s living flesh, which can be proved deadly if left untreated.

According to the CDC, “One female can lay 200 – 300 eggs at a time and may lay up to 3,000 eggs during her 10- to 30-day lifespan. Eggs hatch into maggots that burrow into the wound to feed on the living flesh. After feeding for about 7 days, larvae drop to the ground, burrow into the soil, and emerge as adult screwworm flies.”

The fatal parasite potentially affects livestock, but it can also infest pets and humans but human cases are rare, not impossible as in August 2025, the first case of New World screwworm affecting a person, who travelled to El Salvador in Central America and then returned to Maryland, was detected in the United States

Talking about the containment strategy, the authorities have established a 20 km quarantine detection zone. Moreover, the USDA is planning to release millions of sterile flies to disrupt the reproductive cycle of NWS.

In a press release, USDA asserted, “The United States has defeated this pest before, and we will do it again.”