Federal agricultural inspectors detected a case of New World screwworm larvae \u2014 maggots that burrow into the flesh of living animals and sometimes humans \u2014 on a 3-week-old calf in south Texas, near the U.S.-Mexico border. Officials anticipated the arrival of screwworm in the United States and say they\u2019re prepared to contain it. <\/p>\n
New World screwworm, also known as Cochliomyia hominivorax, is starkly different from the average maggot that feeds on decaying organic matter such as garbage, rotting food or dead animals, said Tom Talbot, veterinarian and member of the California Cattlemen\u2019s Assn. <\/p>\n
That\u2019s because a screwworm larva \u201cattacks living flesh,\u201d Talbot said. <\/p>\n
On Thursday, the U.S. Department of Agriculture confirmed the detection<\/a> of New World screwworm in the umbilical area of a bovine in Zavala County, Texas, more than 60 miles from the northern Mexico border. <\/p>\n As of Friday morning, there have been no additional cases of infected animals reported. <\/p>\n Screwworm is endemic in South America and parts of the Caribbean, according to the Centers for Disease Control and Prevention. However, the parasitic fly has been steadily moving north from Central America to Mexico since 2023. <\/p>\n The USDA says it has actively monitored the fly\u2019s movement. Last month, the USDA was aware of more than 200 active screwworm infestation cases in the border states of Nuevo Le\u00f3n and Tamaulipas, according to Mexico\u2019s Secretary of Agriculture and Rural Development dashboard<\/a>. There are currently more than 2,000 active cases throughout Mexico. <\/p>\n It was believed that the New World screwworm would enter the U.S. in 2025, \u201chowever, thanks to the hard work across the entire Trump administration and our industry, state, and local partners, we were able to buy time for this moment,\u201d said Dudley Hoskins, undersecretary for Marketing and Regulatory Programs for the USDA, in a statement. <\/p>\n The potential economic impact of New World screwworm on the cattle industry due to import restrictions, reduced productivity and animal loss is substantial, said Sally DeNotta, director of the University of Florida\u2019s Equine Performance Laboratory. <\/p>\n Last year, 175 key agricultural organizations signed a letter<\/a> urging additional federal funding for screwworm-control measures, emphasizing USDA estimates that a New World screwworm outbreak in the U.S. could cost producers $4.3 billion annually and cause economic losses of more than $10.6 billion across the southern United States.<\/p>\n \u201cWhile the fly does not survive at temperatures at or below freezing, infected animals could carry the parasite northward and spread infection during the summer months, and the temperate climate of Southern California could certainly support year-round New World screwworm populations,\u201d DeNotta said. <\/p>\n Talbot said from the federal to the local level, everyone in the ranching community has been talking about the arrival of screwworm and how to combat it. <\/p>\n \u201cMy expectation is that there will be a minimal number of cases of [New World screwworm] in California,\u201d he said. <\/p>\n That\u2019s because there are several stations on the border in Southern California, he said, that are collecting data, monitoring for any incidents of the parasitic fly and trapping them. <\/p>\n Talbot says he\u2019s confident that the proactive measures on behalf of the federal government will mitigate the screwworm\u2019s reach and therefore not impact the beef supply locally or nationally. <\/p>\n How screwworm infection spreads<\/p>\n Female screwworm flies are attracted to the smell of wounds \u2014 that can be as small as a tick bite \u2014 and body openings such as the nose, eyes, ears and mouth where they can lay eggs, according to the CDC.<\/a> <\/p>\n A female screwworm fly can lay 200 to 300 eggs at a time and may lay up to 3,000 eggs during her 10 to 30-day lifespan.<\/p>\n When the eggs hatch into maggots, the maggots eat live tissue, causing a worsening, often painful and foul-smelling wound, according to the CDC. <\/p>\n Screwworm has hit the United States before<\/p>\n There was a screwworm outbreak in the southwestern region of the United States in 1965 that prompted Mexican and U.S. livestock producers to sign a declaration to establish a joint program for the eradication of the screwworm from the states on either side of the Mexico-U.S. border, according to the National Agricultural Library<\/a>. <\/p>\n By 1966, the United States had eradicated screwworms, but livestock remained vulnerable to reinfestation from screwworms migrating from Mexico. <\/p>\n Eradication was possible through the sterile insect technique, which uses gamma radiation to irradiate screwworm pupae and create sterile male flies.<\/p>\n The U.S. Department of Agriculture\u2019s Animal and Plant Health Inspection Service maintains a screwworm pupae sterilization facility in North America and is currently building a new center in southern Texas<\/a>. <\/p>\n When produced and released in large numbers, sterile male flies mate with wild female flies, which then lay unfertilized eggs, according to the USDA. <\/p>\n \u201cSince female screwworm flies normally mate only once, the population progressively reduces and is, ultimately, eradicated,\u201d according to USDA officials<\/a>. <\/p>\n