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First Human Flesh-Eating New World Screwworm Case Confirmed in U.S.

New World screwworm larva, like the one pictured, will hatch and feed on the flesh of living animals, typically cattle. Cases in humans are rare but can be fatal.
AP/USDA Agricultural Research Service
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New World screwworm larva, like the one pictured, will hatch and feed on the flesh of living animals, typically cattle. Cases in humans are rare but can be fatal.

Scientists eradicated New World screwworms in the U.S. and Mexico half a century ago by releasing hundreds of millions of sterile adult flies that mated with females and prevented them from laying eggs. Exceptions have included the costly and destructive 1976 outbreak.

For the first time in decades, a case of the deadly New World screwworm has been confirmed in a human in the United States. As Texas Public Radio reports, health officials say the patient became infected after traveling in Central America and was diagnosed after returning home. Reuters reports the patient received medical treatment in Maryland. Due to patient privacy laws, health officials have not released further personal details.

New World Screwworm Life Cycle
New World Screwworm Life Cycle

The screwworm is a flesh-eating parasite that lays eggs in open wounds. The larvae can cause severe tissue damage and even death if untreated. The discovery is raising alarms because the screwworm was eradicated from the U.S. in the 1960s after a massive government program.
Beyond the danger to people, the parasite is a major threat to livestock. Texas ranchers still remember the enormous losses before eradication — screwworms attacked cattle, costing the industry millions of dollars each year. The USDA is now ramping up a massive program to fight the spread of screwworm.

Scientists were able to eradicate the New World screwworm in the 1960s and ‘70s by releasing hundreds of millions of sterile adult flies that would mate with the females, ultimately preventing them from laying viable eggs; and it worked. This strategy created a so-called “barrier zone” that kept the parasites from reentering Mexico and the United States, except in rare cases.
In 1976, for example, more than 1.4 million cattle and hundreds of thousands of sheep and goats became infects during a screwworm outbreak in Texas. According to USDA analysts, if such an outbreak took place today, it would cost the Texas economy $1.8 billion.

A surge in cases is now being reported in Central America, with some cases as far north as 700 miles from the U.S. border in remote farms in Mexico.

Originally from the Pacific Northwest, and a graduate of the University of Washington, Jeff began his on-air broadcasting career 33 years ago in the Black Hills of South Dakota as a general assignment reporter.
David Martin Davies is a veteran journalist with more than 30 years of experience covering Texas, the border and Mexico.