New World screwworm parasite re-emerges in the United States

The New World screwworm, a parasitic fly known as Cochliomyia hominivorax, has re-emerged in the United States after being eradicated in 1966. The parasite has spread northward through Central America and Mexico, reaching U.S. borders due to warming climates and the international movement of livestock.

Unlike most fly larvae that feed on decaying matter, screwworm larvae burrow into and consume living tissue. They are attracted to small wounds, surgical incisions, tick bites, and mucous membranes in all warm-blooded animals, including livestock, wildlife, and humans. If left untreated, the infestations can cause deep, painful wounds and death.

Historically, the United States successfully eliminated the pest using the sterile insect technique, a biological control method where millions of radiation-sterilized male flies were released to collapse the wild population. This effort previously established a biological barrier in Panama to protect North America.