US screwworm cases rise to 15 as infections spread
New sterile fly facility not due online until late 2027
22 June 2026
1 minute read
By: The number of US cases of New World screwworm has risen to 15 after three more animals tested positive in Texas, Reuters reported, citing a social media post from the US Department of Agriculture on Sunday.
The USDA announcement comes nearly three weeks after the first domestic screwworm infestation in six decades was found in a Texas calf.
New World screwworm is a parasitic fly that eats warm-blooded animals alive and can infect livestock, pets, wildlife and, in rare cases, people. The larvae burrow into the living tissue of animals and cause severe wounds that can eventually kill, leading to signficant economic losses for ranchers.
The USDA said it will continue aggressive eradication efforts in affected areas, including the dispersal of tens of millions of sterile flies that halt screwworm reproduction.
One lamb in Crockett County and two calves in Edwards County, Texas tested positive for screwworm in the past 24 hours, according to the USDA's Sunday evening post on X.
Texas ranchers have been bracing for screwworm to cross into the US for the past year, as the pest advanced north in Mexico. Experts have predicted that a widespread outbreak could cost the state $1.8 billion in economic damage and devastate wildlife.
The USDA broke ground in April on a facility to produce sterile flies, which experts describe as the best tool for combating the pest, but it will not come online until late 2027.
