The U.S. confirms its first human case of New World screwworm. What’s it?

The U.S. has confirmed its first human case of the New World screwworm, a flesh-eating parasite whose northward creep from South America has put the nation’s cattle trade on excessive alert in current months.

The Facilities for Illness Management and Prevention (CDC), in coordination with the Maryland Division of Well being, confirmed the case on Aug. 4 in a affected person who had returned from journey to El Salvador, Division of Well being and Human Providers spokesperson Andrew Nixon advised NPR on Monday.

“This is the first human case of travel-associated New World screwworm myiasis (parasitic infestation of fly larvae) from an outbreak-affected country identified in the United States,” Nixon mentioned. “Currently, the risk to public health in the United States from this introduction is very low.”

David McAllister, a spokesperson for the Maryland Division of Well being, confirmed to NPR that the person — a resident of Maryland — has recovered from the an infection.”The investigation confirmed there is no indication of transmission to any other individuals or animals,” he wrote, calling the detection a “timely reminder for health care providers, livestock owners and others to maintain vigilance through routine monitoring.”

The New World screwworm is a species of parasitic flies usually present in South America and the Caribbean, based on the CDC. Infestation happens when fly larvae feed on the tissue or flesh of warm-blooded animals, primarily livestock and, hardly ever, people.

“It’s a fly, and it’s the larvae that does the damage,” says Max Scott, a professor within the Division of Entomology and Plant Pathology at North Carolina State College.

He says infestation in people might be “quite painful,” with excessive mortality charges if left untreated.

“Because once an infestation starts, that often attracts more flies that lay more eggs,” he explains. “And depending where the wound is, the maggots can make their way into vulnerable tissue like the brain, or the wound can get quite big and then you get sepsis.”

However, Scott says, screwworm is an insect, not a virus — so it isn’t contagious.

The pest poses a a lot larger threat to livestock, and up to now yr has been detected in cattle farms in Mexico. Because the New World screwworm will get nearer to the U.S. border, federal authorities have taken a sequence of steps to eradicate the risk — which they did efficiently within the mid-Twentieth century.

What precisely is New World screwworm? 

Screwworms are a sort of blue-gray blowfly that look similar to black flies discovered within the U.S.

The distinction is that screwworms — particularly females — lay their eggs in dwell animals, often in a wound or one other entry level like a nasal cavity.

“The females can lay up to, like, 200 eggs at a time,” Scott says. “And then when the eggs eat, they eat the animal alive.”

After feeding, the larvae fall into the bottom, burrow into the soil and emerge as grownup screwworm flies, persevering with the cycle.

The parasites are named after the screw-like method they burrow into tissue utilizing their sharp mouth hooks. Their Latin title, Cochliomyia hominivorax, “literally means maneater,” Scott says.

“It was named after a sort of unfortunate number of cases in the French penal colony of Devil’s Island back in the 19th century,” he explains.

Human circumstances are comparatively uncommon today, although counts are rising in some elements of South America.

The U.S. Embassy in Nicaragua mentioned in July that it had confirmed 124 circumstances up to now yr. In June, the U.S. Embassy in Costa Rica confirmed its seventh case since 2023 — and first human loss of life “since at least the 1990s.”

How was screwworm eradicated — and why is it spreading now? 

Screwworm was once within the U.S., primarily in Florida, Texas and, throughout the summer time, typically as far north because the Dakotas, Scott says.

Within the Fifties, scientists with the U.S. Division of Agriculture (USDA) pioneered a way of combating them generally known as the sterile insect approach, which Scott calls “one of the great success stories of the USDA of the 20th century.”

As an alternative of utilizing broad-spectrum pesticides, they determined to make use of the pest itself as a management agent. That includes mass-rearing bugs inside factories, sterilizing them with radiation after which releasing them — both from the bottom or, as is the case at the moment, by “planes that fly very precise routes.”

“If the females on the ground mate with a sterile male, at least with a screwworm, that’s all they’ll mate with … so that female won’t produce any offspring,” Scott says.

By way of this system, the U.S. managed to eradicate New World screwworm in 1966. Mexico adopted swimsuit within the Nineteen Seventies, and Central America within the early 2000s. The U.S. additionally used this methodology to eradicate what the CDC calls a “small outbreak” within the Florida Keys in 2017.

“Over a 50-year period, screwworm was pushed back from the United States through Mexico, through Central America, to the Panama-Columbia border. That was about 20 years ago,” Scott says. “It was stopped at the border and then was held for a long time until the barrier broke and screwworm came back.”

Panama, Costa Rica, Nicaragua and Honduras have documented new circumstances lately, fueling considerations of a northward unfold.

Scott says there are most likely a number of explanations, together with the motion of infested cattle and the chance that the present pressure of sterilized flies is much less efficient than up to now. The hope, he says, is {that a} larger crop of sterilized bugs will be capable to include the screwworm risk to southern Mexico, earlier than it may possibly attain the U.S.

What’s the U.S. doing about screwworm? 

The U.S. briefly halted dwell cattle imports from Mexico in November, after a constructive case was detected there.

It lifted the ban in February however reinstated it on a month-by-month foundation in Might, with Agriculture Secretary Brooke Rollins citing “the continued and rapid northward spread of New World Screwworm (NWS) in Mexico.” She mentioned it had been detected in farms as far north as Oaxaca and Veracruz, some 700 miles from the U.S. border.

Within the months since, the federal authorities has confronted mounting stress from agricultural teams anxious about the specter of screwworm and its potential influence on the provision chain. In an early August letter to Rollins, they used USDA estimates to calculate {that a} modern outbreak may trigger a complete financial lack of greater than $10.6 billion.

The USDA seems to have heard these considerations. Earlier this month, it introduced sweeping plans to fight the unfold of screwworm, together with constructing the U.S.’ solely sterile fly manufacturing facility at an air power base in Edinburg, Texas. It says it’s going to produce as much as 300 million sterile flies per week.

Scott says at its peak, the half-century eradication marketing campaign was run from a facility in Mexico that might produce no less than 500 million sterile flies per week. It was shut down for financial causes in 2012. There’s at present just one such facility in operation, in Panama, with a most capability of some 100 million flies per week.

Asserting the brand new initiative in Texas, Rollins didn’t specify when the plant will probably be operational, however has beforehand mentioned it’s going to take two to 3 years to construct, Reuters studies. The USDA can also be supporting a separate facility in Mexico that’s slated to open in 2026.

Different steps the USDA says it’s going to take embody ramping up the hiring of USDA-employed mounted patrol officers, known as “Tick Riders,” to deal with border surveillance; coaching canine to detect screwworm infestations in livestock on the border and investing $100 million in applied sciences to fight screwworm.

Agricultural teams welcomed the announcement. Zippy Duvall, president of the American Farm Bureau Federation, mentioned in a press release that the introduction of New World screwworm within the U.S. would solely exacerbate an already-volatile cattle market.

“It took decades to eradicate this parasite from within and adjacent to our borders more than a generation ago, and this is a proactive first step,” he added.