The New World screw worm has been detected in Texas for the first time in decades, according to the U.S. Department of Agriculture (USDA). Nine cases have been confirmed in cattle, goats, and a dog, prompting federal and state authorities to implement containment measures. The parasitic fly, which lays larvae in open wounds, can cause severe infections and death if untreated. The FDA has approved antiparasitic medications for affected animals, including ivermectin and moxidectin, as part of the response.
What is the New World Screw Worm?
The New World screw worm (Cochliomyia hominivorax) is a parasitic fly whose larvae infest wounds in mammals, feeding on living tissue. Native to Central and South America, it was eradicated from the U.S. in 1982 through a combination of sterile insect technique and pesticide use. The parasite re-emerged in 2016 in Florida and Texas, with the latest cases reported in 2023. According to the USDA’s Animal and Plant Health Inspection Service (APHIS), the current outbreak involves cattle, goats, and a dog, with no human infections confirmed.
Outbreak Details and Affected Animals
Texas Animal Health Commission (TAHC) officials reported nine confirmed cases in 2023, including three cattle, five goats, and one dog. The animals showed signs of myiasis, a condition caused by larval infestation, which can lead to systemic infections and mortality without treatment. The USDA emphasized that the parasite spreads through fly transmission, with larvae developing in wounds caused by injuries, surgeries, or other skin breaches.
FDA-Approved Treatments and Containment Efforts
The FDA has authorized the use of ivermectin and moxidectin for treating screw worm infestations in dogs and cats, while cattle are managed through veterinary-prescribed antiparasitic drugs. APHIS is deploying surveillance traps and urging livestock owners to monitor animals for wounds. “Early detection is critical,” said a TAHC spokesperson. “Farmers should inspect animals daily and seek veterinary care if lesions are found.” The agency is also collaborating with the Texas Veterinary Medical Association to educate ranchers on prevention.
Why This Outbreak Matters
The re-emergence of the New World screw worm highlights risks to livestock health and agricultural economies. In 2016, the parasite cost U.S. farmers an estimated $1 billion in losses. While the current outbreak is smaller, experts warn that climate change and shifting ecosystems could increase the fly’s range. A 2022 study in *Parasites & Vectors* noted that warmer temperatures may extend the parasite’s breeding season, underscoring the need for ongoing vigilance.
Prevention and Public Health Measures
The USDA advises farmers to keep animals in enclosed spaces during peak fly activity (dusk to dawn) and to treat wounds promptly. The FDA also recommends avoiding the use of untreated animal hides, which can harbor larvae. Public health officials stress that the parasite does not transmit to humans but remains a threat to animal populations. “This is a reminder of the delicate balance between wildlife, agriculture, and public health,” said Dr. Sarah Mitchell, a veterinary epidemiologist at Texas A&M University. “Proactive measures are our best defense.”