The U.S. Department of Agriculture (USDA) confirmed the detection of the New World screwworm in a three-week-old calf in Zavala County on June 3. Since this initial case, the agency has reported additional screwworm infestations across Texas.
This parasitic fly presents a significant challenge, posing a multibillion-dollar crisis for Texas's cattle industry, which generates $41 billion annually. The outbreak also carries the potential to further increase already record-high beef prices nationwide. While the full extent of the current outbreak in Texas remains unclear, Mexican officials have reported nearly 28,000 cases in Mexico since November 2024.
State and federal officials have been actively tracking the northern migration of the screwworm since 2023. In response to the confirmed cases, the USDA and the Texas Animal Health Commission (TAHC) have implemented heightened animal surveillance measures around detection sites. These agencies have established zones around each infestation, restricting animals from leaving these areas without proper inspection.
Control efforts are also being intensified through several strategies. Officials are increasing the deployment of fly traps, expanding surveillance of wildlife, and releasing sterile flies. The release of sterile flies is a key tactic designed to disrupt the reproduction cycle of the parasitic screwworm fly, thereby limiting its spread.
New World screwworm is a parasitic fly attracted to living tissue. Its larvae burrow into open wounds, where the maggots feed off the living flesh, causing severe damage to the host animal. If left untreated, these infestations can be fatal. The screwworm can also penetrate the skin through other openings, such as the corner of an eye or through the nose.
From a biological standpoint, all mammals, including pets and humans, are vulnerable to screwworm infestations. However, livestock and wildlife are particularly susceptible because they spend their entire lives outdoors, increasing their exposure. Dogs and cats can become vulnerable through small wounds or scratches that break the skin.
Veterinarian Casey Locklear, who serves as the parasiticides lead for Elanco Animal Health, advises pet owners to keep their pets on year-round medication for fleas and ticks. Locklear emphasized the importance of early detection and treatment: “As a pet owner, if you were to notice that your dog or cat had a wound, especially if it’s foul smelling, it’s enlarging, you may actually see the maggots.” She concluded that, whether for oneself or a pet, "early treatment is key."
As officials continue to monitor and respond to the outbreak, the collaborative efforts between the USDA and the Texas Animal Health Commission will focus on containing the spread through ongoing surveillance, inspections, and biological control methods to protect both the state's vital agricultural industry and its animal populations.
