Tag: Cattle

Authorities Confirm First Screwworm Case in U.S. in 60 Years

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flies sitting on cow

A flesh-eating, parasitic worm has been discovered in the United States once again, according to officials. In a post to social media on Wednesday, June 3, U.S. Secretary of Agriculture Brooke Rollins confirmed the presence of Cochliomyia hominivorax, the New World screwworm fly, also known as the New World screwworm or simply screwworm. “As expected, @USDA_APHIS confirmed the detection of a New World Screwworm (NWS) fly in a 3 week old bovine in Zavala County, Texas,” she tweeted Wednesday.  stock image of Screwworm larva.

Alamy “@USDA and Texas Animal Health @TAHC officials are taking immediate action to contain and eradicate NWS from the area,” Rollins continued.  Her message was an update, alerting the public that she had already met with approximately 50 Texas cattle ranchers to discuss the development in the southern part of the state.  Screwworms were “largely eradicated” in America in the 1960s, the Food and Drug Administration previously said. However, a person who traveled to El Salvador in Central America and then returned to Maryland in August 2025 was the first case of a human being infected in years. The U.S. Department of Agriculture also shared a statement, calling screwworms “a devastating pest.”

 “It can cause serious, often deadly damage to animals and people in areas where the pest spreads. While NWS is present in parts of South America—where infections in animals and people continue to occur—it was eradicated from the United States decades ago. In recent years, NWS has moved northward through Central America and Mexico,” the agency said of the New World screwworm.The New World screwworm is a fly that lays eggs in open wounds and body openings, according to the Centers for Disease Control. The parasite typically finds points of entry through the eyes, ears, nose, mouth, or genitals of warm-blooded mammals. Once the eggs hatch, they turn into maggots that burrow into the host and feed on its flesh. 

Even small breaks in the skin can be enough for the screwworm to lay eggs in, according to the CDC. “One female can lay 200 – 300 eggs at a time and may lay up to 3,000 eggs during her 10- to 30-day lifespan,” per the CDC. “Eggs hatch into maggots that burrow into the wound to feed on the living flesh. After feeding for about 7 days, larvae drop to the ground, burrow into the soil, and emerge as adult screwworm flies.”If a maggot has burrowed into an opening in your body, it is important to have a health care provider remove them.

Do not attempt to do it yourself. If a screwworm is removed from your person, do not leave it on the ground. It should be placed in a leak-proof container with rubbing alcohol to kill the parasite. Live maggots should also not be left in trash bags, as they can still escape and spread.The USDA said sterile flies are one of the ways they have been able to combat screwworms. In a press release Wednesday, the agency specified that the screwworm had been found inside a 3-week-old calf’s umbilical area. The case marked the first time it’s been detected in the U.S. since 1966.

“USDA invested heavily in the tools needed to eliminate NWS ever since cases started increasing in Central America and Mexico,” the agency said. “The United States has defeated this pest before, and we will do it again.”

Source: Authorities Confirm First Screwworm Case in U.S. in 60 Years

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