Caribbean coral catch disease from sewage

(NPR): A bacterium from our guts is now rampaging through coral reefs in the Caribbean. Those reefs were already in slow decline, but they took a huge hit starting in 1996, when a disease called white pox appeared in the Florida Keys. "Since that time, elkhorn coral — the species it affects — has declined 88 percent in the Florida Keys," says Kathryn Sutherland, a reef ecologist at Rollins College in Florida. "And we've seen similar declines elsewhere in the Caribbean." The coral is named for its resemblance to elk antlers, and is among the most important reef-building species in the Caribbean. Sutherland and her colleagues soon found a culprit for the die-off — a bacterium called Serratia marcescens.

It also happens to cause disease in human beings, notably hospital infections. But the scientists couldn't prove cause and effect. “In 2002, we could only speculate that human waste was the source of the pathogen because the pathogen is also found in the guts of other animals," such as deer, Sutherland says.

So she and some colleagues exposed the coral in the laboratory to bacteria extracted from sewage. As they report in the journal PLoS ONE, the coral got the pox within days. "That gave us definitive evidence that white pox disease is caused by a pathogen found in human sewage."

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