Texas Governor Greg Abbott has declared a statewide disaster after authorities confirmed a second case of the New World screwworm parasite in a calf in Zavala County on June 5. This discovery, following an initial case identified on June 3 in a three-week-old calf near La Pryor, approximately 30 miles from the Mexican border, marks the first known U.S. outbreak of the destructive parasite in decades. The declaration mobilizes state resources and enhances coordination among agencies to prevent the screwworm's spread into Texas's substantial livestock industry.
"This pest poses a significant threat to Texas livestock, wildlife, and the broader agricultural economy." — State Officials
The New World screwworm (Cochliomyia hominivorax) is a highly damaging livestock parasite. Unlike typical fly larvae that feed on decaying tissue, screwworm larvae consume living flesh, causing deep, festering wounds that can lead to severe infection, permanent injury, or death if left untreated. The first infected calf was found near La Pryor, and the second, about one month old, was located approximately 5.6 miles away, indicating a localized but concerning presence.
The rapid response from state and federal agencies underscores the gravity of the threat. Governor Abbott's disaster declaration authorizes the deployment of state resources, prioritizes emergency response efforts, and strengthens inter-agency collaboration. "This pest poses a significant threat to Texas livestock, wildlife, and the broader agricultural economy," state officials affirmed as containment operations scaled up.
A 20-kilometer quarantine zone has been established, encompassing parts of Zavala and Uvalde counties. Within this zone, movement restrictions are now in effect for livestock, wildlife carcasses, and any other warm-blooded animals that could potentially facilitate the parasite's spread. These measures are critical to isolating the current infestation and preventing its expansion.
The United States successfully eradicated the New World screwworm in 1966 through a massive federal campaign. This effort largely relied on the Sterile Insect Technique (SIT), a method where millions of male screwworm flies are bred in specialized facilities, sterilized using radiation, and subsequently released into the wild. Since female screwworm flies mate only once, breeding with sterile males results in no viable offspring, gradually leading to a collapse of the wild population.
State and federal officials are once again employing the SIT strategy. Facilities in Texas are actively producing and releasing millions of sterile flies weekly to disrupt the parasite's reproductive cycle and halt its advance. Additionally, more than 8,000 monitoring traps have been strategically placed along the southern border to detect any further infestations.
Agricultural experts have warned about the potential for devastating consequences should this outbreak become uncontrolled. Before the successful eradication efforts in the 1960s, screwworm infestations were responsible for significant livestock losses across the southern United States. Animals frequently suffered extensive tissue damage, substantial weight loss, secondary infections, and often death. Wildlife populations were also severely affected, with historical outbreaks in Texas causing mortality rates exceeding 50 percent among white-tailed deer and other game species in some areas.
The current outbreak follows a northward migration of the parasite, which began around 2023, moving through South America, Central America, and Mexico. Texas, being the leading state in cattle production nationwide, is particularly vulnerable to the economic disruption that a widespread infestation could inflict.
The Texas Animal Health Commission (TAHC) and the Texas Parks and Wildlife Department (TPWD) are spearheading the response through a specialized New World Screwworm Response Team. Officials are urging ranchers, veterinarians, hunters, and all animal owners to meticulously inspect their animals for any unusual wounds, signs of larvae, or other indications of infection. Prompt reporting of any suspected cases is considered crucial to the success of the containment efforts. While the outbreak currently remains limited to two confirmed cases, authorities emphasize that aggressive and coordinated containment measures are vital to avert a larger crisis for Texas agriculture and livestock producers across the nation.
