By Mackenzie Tatananni
The first case of New World screwworm, a flesh-eating fly that typically feeds on livestock, has been detected a calf in Texas -- the first U.S. case in six decades.
The discovery has very real implications for America's ranchers and meat processors. Earlier this year, the U.S. beef cattle herd reached a 75-year low. The head count was 86.2 million, down from 86.5 million in just 12 months.
The shortage is driving up livestock prices. Both ranchers and meat processors are seeing their profits shrink.
The calf with the worm was about 50 miles from the U.S.-Mexico border, officials said. The parasitic fly lays its eggs on warm-blooded animals, where the hatched maggots burrow into and feed on the flesh.
New World screwworm is endemic to South America and parts of the Caribbean. Today, there are outbreaks in Mexico and Panama. As of early May, Mexico had 1,717 active cases, according to the government. Panama has stopped tracking individual cases because there have been so many since its outbreak started in 2023. Earlier this year, the number of cases and complaints totaled more than 6,000, according to officials there.
The U.S. halted all livestock imports from Mexico during an outbreak in May 2025, and the ban remains in place. The fly was officially eradicated from the U.S. in 1966.
America's beef shortage could last another two years, a long time for the ranchers and meat processors already feeling the squeeze.
Two of the largest processors in the country, Tyson Foods and JBS, said last month that soaring livestock prices are taking a big bite out of them.
The U.S. ban "has placed incremental pressure on beef supplies over the last year," Raymond James analyst Brian Vaccaro wrote, adding that the New World screwworm "limits visibility as to when cattle imports may resume."
Shares of Tyson and JBS are both in the red for the year, down 2.6% and 16%, respectively. The benchmark S&P 500 has gained 10%.
Shoppers are feeling the tension, too. As of April, the average price for steak was $13 a pound, up from $8.70 five years ago, according to the Labor Department.
Restaurants are grappling with the high prices, too. Steak restaurants -- Texas Roadhouse, Outback Steakhouse, and LongHorn Steakhouse, for example -- are the most vulnerable because beef is such a big part of their costs.
And fast-food chains Wendy's and Burger King are particularly sensitive because burgers are their core menu. Wendy's, in fact, is pushing much-cheaper chicken to help offset beef inflation.
Another sector paying attention to the Texas calf is animal health.
On Thursday, Elanco Animal Health. described the finding as a threat "that has not been seen north of the Florida Keys since the fly was eradicated from the United States more than 50 years ago."
Elanco has six products targeting screwworm larvae, including an aerosol wound treatment sanctioned by the Environmental Protection Agency. In pets, Elanco's family of Credelio tablets for dogs and cats have been granted either conditional approval or emergency use authorization from the Food and Drug Administration.
Peers Zoetis and Merck are also positioned to benefit. Zoetis manufactures an injection called Dectomax-CA1, which the FDA has given conditional approval for use in cattle. Merck Animal Health offers a pour-on solution targeting screwworm infections.
Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com
This content was created by Barron's, which is operated by Dow Jones & Co. Barron's is published independently from Dow Jones Newswires and The Wall Street Journal.
(END) Dow Jones Newswires
June 04, 2026 16:22 ET (20:22 GMT)
Copyright (c) 2026 Dow Jones & Company, Inc.
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