ORLANDO, Fla. \u2013 One of the most devastating parasites in Florida\u2019s history has once again been detected in the Sunshine State.<\/p>\n
In a release last year<\/a>, the Florida Department of Agriculture and Consumer Services announced that the New World Screwworm (NWS) had been moving northward through Mexico, posing a huge threat to the U.S.<\/p>\n But just last week<\/a>, the USDA announced that a horse from Argentina had been presented for routine importation at a quarantine facility in Florida. There, officials found an open wound with NWS larvae.<\/p>\n [BELOW: New World Screwworm may be poised for a return to the U.S.]<\/p>\n However, Texas Ag Commissioner Sid Miller cautioned Florida residents not to panic.<\/p>\n \u201cI want to set the record straight on the recent New World Screwworm detection in Florida,\u201d he said<\/a>. \u201cThis detection did not constitute evidence of a U.S. outbreak or domestic New World Screwworm infestation. It was thankfully caught during a routine inspection of an imported horse arriving from a country south of the Dari\u00e9n Gap.\u201d<\/p>\n (Left) New World Screwworms; (Right) Blowflies were sterilized in the 1950s to help eradicate screwworm infestations in Florida (Florida Department of Agriculture and Consumer Services\/Florida State Archives)<\/p>\n Per experts, the NWS are maggots that often enter animals through open wounds, feeding on an animal\u2019s living flesh. As a result, infestations can be fatal if not treated.<\/p>\n \u201cThe New World Screwworm<\/a> \u2014 a destructive parasite that targets warm-blooded animals \u2014 was eradicated from the U.S. more than four decades ago,” state officials announced. \u201cIts return would pose a serious threat to livestock, wildlife, and domestic animals, particularly in states like Florida with warm climates and abundant animal populations.\u201d<\/p>\n Experts state that screwworm eggs are deposited in a \u201cshingle-like manner\u201d at the edges of superficial wounds, with larvae feeding by burrowing into the wound like a screw \u2014 hence the name<\/a>.<\/p>\n An illustration depicting a larvae infestation, showing how the “screwworm” burrows into its host (U.S. Department of Agriculture)<\/p>\n While the NWS had been present in the southwestern U.S. since at least 1842, it was first documented as a major problem in 1933 after shipments of infested animals came in from the region.<\/p>\n At the time, the federal government and the state of Florida began developing tactics to deal with the threat, such as education programs, special insecticides, and radiation to sterilize the insects.<\/p>\n 450 sterile screwworm pupae in a typical paper box “bomb” to be dropped on a cattle ranch by plane in 1958 \u2014 just one of the methods to fight back against New World Screwworm infestations in Florida (Florida State Archives (Public Domain))<\/p>\n But in the meantime, producers lost out on tens of millions of dollars each year as the NWS ravaged livestock, data shows.<\/p>\n Eventually, the U.S. and Mexico worked together to push these infestations down to the southern borders of Mexico in 1986. <\/p>\n There was a brief reemergence in the Florida Keys affecting the endangered Key deer back in 2016, though the outbreak was ultimately eradicated.<\/p>\n In this Feb. 12, 2013, file photo, a key deer walks out of the woods on Big Pine Key, Fla. Florida\u2019s agriculture commissioner said Thursday, March 16, 2017, that the state anticipates winning its fight against flesh-eating maggots threatening endangered deer in the Florida Keys. (AP Photo\/J Pat Carter, File) (Copyright 2017 The Associated Press. All rights reserved.)<\/p>\n However, Florida officials said that infestations have been spreading north from Panama since 2023, increasing the risk of this pest being reintroduced to the U.S.<\/p>\n As a result, health experts have been urging residents to keep an eye out for any signs of their return.<\/p>\n \u201cThis is about protecting American agriculture, plain and simple,\u201d Florida Commissioner of Agriculture Wilton Simpson said. \u201cWe know how costly and dangerous this pest can be if it takes hold. We\u2019re calling on Florida\u2019s producers, veterinarians, and animal health professionals to remain aware and act quickly if they suspect something unusual.\u201d<\/p>\n Recent New World Screwworm detections in Mexico (U.S. Department of Agriculture)<\/p>\n Last summer, federal officials rolled out a plan<\/a> to preemptively combat the NWS by pushing eradication efforts in Mexico and setting up a facility in South Texas that can disperse sterile flies.<\/p>\n Later on, the USDA announced that it would be closing U.S. southern border ports<\/a> to livestock trade as the infestation moved further northward. In 2025, the first case was reported domestically<\/a> out of Maryland.<\/p>\n [BELOW: Florida woman gathers cold-stricken iguanas that fell from trees]<\/p>\n That said, Commissioner Miller explained that no outbreaks of NWS in the wild have yet been discovered in the U.S. As such, the risk to public health at the time of writing is still very low.<\/p>\n Signs of screwworm infestation in animals include the following symptoms:<\/p>\n Wounds in living animals infested with maggots<\/p>\n Blood-tinged discharge from the infested wounds<\/p>\n Foul odor<\/p>\n Discomfort<\/p>\n Depressed\/no eating<\/p>\n Decreased milk production<\/p>\n Seclusion from rest of herd or flock<\/p>\n