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Screwworm

Scientific Name

Cochliomyia hominivorax (Coquerel) (ITIS; name is valid but unverified)

Common Name

New World screwworm, primary screwworm

Native To

South America and the Caribbean (CFSPH 2012)

Date of U.S. Introduction

Eradicated in the U.S. in 1966 (ARS 1992)

Means of Introduction

Could be reintroduced to the U.S. from an infested animal (CFSPH 2012)

Impact

Parasite that kills livestock and wildlife, particularly cattle (CFSPH 2012)

Current U.S. Distribution

Not currently established

Screwworm, larva(e)

Screwworm, larva(e)

Credit

Photo by Lesley Ingram

Find more images

Spotlights

  • APHIS History Highlights: APHIS and Mexico Take On Deadly Screwworm

    • Apr 12, 2022
    • USDA. Animal and Plant Health Inspection Service.

    • In the early 1970s, USDA's progress in eradicating screwworm—among the deadliest and most vicious of livestock pests—was at a crossroads. Department scientists had revolutionized the country's battle against the insect by creating a new technology. The concept was simple yet profound: rear and aerially distribute masses of sterile screwworm flies in infested areas, so the resident fly populations would have increasing difficulty reproducing—and eventually breed themselves out of existence. The new approach worked so well that by 1966, USDA declared screwworm eradicated within U.S. borders.

  • ARS Science Key to Stopping ‘Man-Eating’ Parasite

    • Jan 4, 2021
    • USDA. ARS. Tellus.

    • Eliminating screwworms from the United States saves farmers and ranchers nearly $900 million in lost livestock each year.

  • USDA Agencies Work Together to Eradicate an Old Foe: the Screwworm

    • Jan 9, 2018
    • USDA. Blog.

    • Early in October 2016, the U.S. Department of Agriculture (USDA) was faced once again with New World screwworm, which had been eradicated from the United States more than three decades ago. Infestation of this flesh-eating parasite was confirmed in deer from the National Key Deer Refuge in the Florida Keys.

      USDA’s Animal and Plant Health Inspection Service (APHIS) immediately began releasing sterile male flies in Florida’s affected areas as part of an aggressive eradication campaign. By March 2017, the screwworm had been successfully eradicated from Florida.

  • A New World Screwworm - A Story Map by USDA

    • USDA. Animal and Plant Health Inspection Service.

    • An interactive story map of the USDA's history of eradicating the infestation and the continuing efforts to keep screwworm out of the US.
      See also: APHIS Interactive Maps to explore plant and animal health or wildlife damage management data

Videos

Selected Resources

The section below contains highly relevant resources for this species, organized by source.

Partnership
Federal Government
State and Local Government
Academic
Citations