The New World screwworm, a flesh-eating parasite, has spread beyond Texas, with new cases confirmed in New Mexico. This development has raised concerns about the potential impact on the cattle industry and wildlife. The U.S. Department of Agriculture (USDA) and other authorities are working to contain the outbreak and protect livestock.
The screwworm is a type of fly larva that feeds on living flesh, unlike typical maggots that feed on dead material. The flies lay their eggs in open wounds of animals, including cattle, wildlife, pets, and occasionally humans. The USDA has a program to breed sterile male flies and release them to mate with wild females, which has been effective in containing the parasite in the past.
New cases confirmed in Texas and New Mexico
As of June 2026, there have been six confirmed cases of the New World screwworm in the U.S. Three calves and a goat in Texas, and a dog in Lea County, New Mexico. The dog had not traveled to Mexico or Texas, so authorities are investigating the property where the pet lived. If infected flies are found, animal inspections in the area will increase.
The first two screwworm cases were discovered in calves in south Texas. A case was announced in a calf in La Salle County, southwest of San Antonio, and in a goat in Gillespie County, west of Austin. In each case, officials have set up a 12-mile quarantine zone to try to slow the parasite’s advance.
Efforts to contain the outbreak
The USDA and the U.S. cattle industry have been working to prevent an outbreak since the screwworm was detected in Mexico late in 2026. The USDA has been dropping sterile flies in south Texas since February and is working to increase sterile fly production in plants outside the U.S. and build a $750 million fly factory in Texas.
The long-term solution to the screwworm problem is breeding sterile male flies. Since wild female flies mate just once, if that encounter is with a sterile male, outbreaks can eventually be halted as the flies die out. The goal is to have enough sterile flies to stop the pests from returning in 2027 after the winter kills off most of them.
Scientists are also working on ways to sterilize only male flies to make the program even more effective. The USDA has established a 24-hour screwworm hotline and a website and map for reported cases. Texas officials have encouraged ranchers to keep a close eye on their herds and local wildlife.
The impact on beef consumers and the cattle industry
Experts have assured beef consumers that the screwworm infections in cattle do not pose a risk to human health. The parasite does not infest meat or fruit, and there is no need to panic. The outbreak marks the first time the screwworm has been detected in the U.S. in decades, but authorities have been tracking the pest for a long time and are prepared to fight it.
The outbreak is not expected to cause beef prices to increase, as they are already at an all-time high due to drought conditions and geopolitical issues. However, the screwworm could devastate the millions of wild white-tailed deer in Texas and other warm-blooded livestock if it is not contained.
The Texas A&M AgriLife Extension Service has launched a New World screwworm task force to protect the cattle industry. The task force is developing new training programs to get more people on the ground to inspect and treat animals, preventing the spread of the parasite.
