Flesh-eating screwworm found in Texas calf: What is it, what are the risk factors, and how to protect your cattle herd

After nearly sixty years, one of the nastiest parasites ever to threaten American livestock is back. The New World screwworm, the flesh-eating invader whose larvae dig deep into living animal tissue, has shown up in a Texas calf, just a few miles from the Mexican border. Officials found the case in Zavala County, and since this hasn't happened in the US since 1966, ranchers, vets, and the cattle industry are all worried.As reported by Reuters, Federal officials have confirmed that a three-week-old calf in South Texas was infected with the New World screwworm, a flesh-eating parasite whose larvae burrow into the living tissue of warm-blooded animals. The case, detected in Zavala County near the Mexican border, marks the first confirmed occurrence of the parasite in the United States since 1966 and has triggered an emergency response from state and federal authorities.The discovery has rattled ranchers, veterinarians, agricultural officials, and livestock markets alike. While authorities insist the outbreak can be contained, the reappearance of a pest that cost billions of dollars before its eradication is being viewed as a major biosecurity challenge for the US cattle industry.Per Reuters, authorities are stating that the outbreak is manageable as of now, but nobody's taking it lightly. Last time screwworms invaded, it cost billions to finally wipe them out. The US cattle business is staring down a big biosecurity headache.What’s striking is that despite the name, there's no worm here. It's actually the young form of a parasitic fly, named Cochliomyia hominivorax. Unlike typical maggots that feed on dead stuff, screwworm larvae eat live flesh. Adult flies lay eggs in open cuts, wounds, or even natural animal openings — think noses, ears, navels, mouths. Once the eggs hatch, the larvae dig further into the tissue, making these wounds bigger and more agonizing.What’s more terrifying is that if left untreated, infestations can kill.Mostly, screwworms attack cattle, sheep, goats, horses, deer, pets, and wildlife. Sometimes, they'll infect people too, which is rare, but not impossible.Back in the 1960s, scientists had a major win against the screwworm when they got rid of it from the US by dumping millions of sterile male flies across the country. Females would mate with those male flies, leaving no next generation, and eventually, the screwworm population crashed. After that, the US kept the parasite out with a biological barrier further south, mostly in Central America.However, of late, that wall has crumbled. Screwworm numbers jumped in Central America and Mexico after barriers failed in Panama, and cases have been popping up across Mexico since late 2024. The pest has been creeping north toward the US, and now Texas has the first confirmed case.One sick calf is just the start. Texas sits at the center of US beef production, as the largest cattle-producing state, but herds are already smaller than ever with drought, disease, costs, and more. A widespread screwworm outbreak wouldn't just hit ranchers, it'd ripple through the whole beef market, and disrupt beef production across the country.In fact, the USDA figures a big Texas outbreak could rack up losses close to $1.8 billion from dead animals, expensive treatment, quarantines, lower productivity, and restricted exports.It’s only understandable that markets reacted right away. After the news broke, traders and ranchers started tracking cattle futures, and everyone's worried about the supply chain if screwworm takes hold.Moreover, it's not just cattle at risk. Screwworms could spread to wildlife, pets, horses — basically, any warm-blooded animal with a wound. Past outbreaks show just how fast this parasite moves.State and federal teams jumped in fast. They've set up quarantine zones, blocked animal movement, launched surveillance, laid traps, and sent in experts to inspect every ranch.They're also back to what worked before: releasing millions of sterilized male flies to stop the parasite from reproducing. This old tactic killed off screwworms decades ago, and it's still the main weapon.Agriculture Secretary Brooke Rollins says that he is confident the case can be contained and has emphasized that officials do not currently expect the infestation to spread coast to coast.First and foremost, the key to preventing the nationwide infestation is strict vigilance. Owners need to check animals for wounds and any weird sores or maggot activity. Clean cuts quickly and keep an eye out. If you spot something odd, like fast-growing wounds or unexplained tissue damage, it’s advisable to contact the vet right away.Pet owners in the south should be watching too. Livestock is the top priority right now, but dogs and other animals can get infected under the right conditions.What’s slightly reassuring is that humans aren't at much risk as of now. However, anyone with a strange wound after visiting affected areas should get medical help.We’re yet to understand the full scale of the screwworm invasion, whether this is just a one-off or the start of something bigger. One could only hope for a healthy and safe outcome with quarantines and surveillance, as sterile flies keep things controlled, and past isolated cases disappear fast.Because in case screwworm starts to settle in, the US is looking at years of expensive eradication battles, dead animals, trade issues, and higher beef prices — and nobody wants that.So far, officials seem cautiously optimistic, because for now, it’s just one calf.However, there’s no safer option than to stay alert.