Flesh-Eating Parasite Returns To The US, Half A Century After Being Eradicated


Ben Taub

Freelance Writer

clockNov 30 2016, 16:53 UTC

The New World screwworm is so called because it resembles a screw as it enters the flesh of its victims. CSIRO via Wikimedia Commons

A gruesome flesh-eating worm has reared its ugly head in the Florida Keys for the first time since the 1970s, when it was eradicated by local agricultural authorities – or so they thought.

The New World screwworm – which is the larva of the screwworm fly and is so called because its twisted body resembles a screw as it delves into the flesh of its victim – reappeared in a herd of endangered Key dear in July, and has since led to the death of 132 of the animals, which is about 15 percent of the population.


Capable of infecting any warm-blooded animal, including humans, the parasite eats away at the body of its host and is particularly damaging to cattle. So far, the infestation has not spread beyond Florida’s southernmost Monroe County, and with no new deaths in the past week, officials are hopeful that the situation is finally under control.

Despite this, a state of agricultural emergency remains in place, and locals are remaining vigilant against any further infections. An animal quarantine program has been running since early October, and deer are being medicated in order to protect them from the screwworm. Sterile male screwworm flies are also being released in order to restrict reproduction.

Given that female flies only mate once in their lifecycles, causing them to do so with infertile males could prevent them from becoming fertilized. When this happens, they lay their eggs in the open wounds of other animals, so that when the larvae hatch they can begin devouring the surrounding flesh.

The fly is typically found across Central America and the Caribbean, and was eradicated in the southeast US around half a century ago, following a hard-fought battle by agriculture agencies in response to a devastating wave of infestations that began in the 1930s.


Authorities believe the parasite was probably brought back into the country by either immigrants or cargo from Cuba or Haiti. Adam Putnam, Florida’s commissioner of agriculture, told the New York Times that “millions of cargo containers and millions of passengers arrive every year, entering and exiting Florida and bringing unwelcome pests and disease with them.”

If the screwworm is not eradicated again, the US Department of Agriculture says it could cause up to $1 billion in cattle losses.

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