A veterinarian's guide to New World screwworm cases, treatment, reporting, response in the US, & more
Drawing on insights shared by federal officials at the USDA, FDA, and CDC during a joint session at the 2026 AVMA Convention, along with the latest federal guidance, agency data, and published resources, this report explains what veterinarians need to know about the flesh-eating parasite.
Cochliomyia hominivorax—also known as New World screwworm (NWS) and dubbed “the flesh-eating parasite”—returned to the United States on June 3, 2026, when the US Department of Agriculture (USDA) confirmed the first domestic case in approximately 60 years, in a calf in Zavala County, Texas.1 Since then, as of July 23, 2026, the USDA's Animal and Plant Health Inspection Service (APHIS) has confirmed 42 US animal cases—21 cattle, 13 sheep, 5 goats, and 3 dogs—across 16 Texas counties and 1 New Mexico county.1