Scientists finally identify a deadly toxin that has been killing birds


For 25 years, A mysterious killer is on the loose in the southern United States, responsible for the deaths of more than 100 eagles and thousands of other birds. The first victims were found in the fall of 1994 and winter of 1995, when 29 bald eagles were killed on or near DeGray Lake, Arkansas. At first, the birds appeared to be intact. But during an autopsy, scientists found lesions in the brain and spinal cord, a condition they called avian vacuolar myelinopathy (AVM). Investigators from the Department of Fish and Wildlife looked for diseases or toxins like DDT that could cause this debilitating disease, but found nothing.

The mystery remained unsolved.

The killer turned up again a few years later in the Carolinas, Georgia and Texas. In addition to bald eagles, it had started attacking waterfowl such as Canadian geese, coots, and mallards. First it made the birds unable to fly. They staggered, their wings fell off, looked catatonic or paralyzed. Then in just five days, they were dead.

Now, in an article published today in Sciences, An international team of researchers from Germany, the Czech Republic and the United States finally identified the culprit, a previously unknown neurotoxin called ethoctonotoxin, which could be produced by a deadly combination of invasive plants, opportunistic bacteria and chemical contamination in lakes and reservoirs.

To find this new toxin, the scientists had to work together as detectives, assessing the crime scene and questioning the suspects. Susan Wilde, a professor of aquatic sciences at the University of Georgia, began investigating the mystery in 2001 when 17 bald eagles died in Lake J. Strom Thurmond, a man-made reservoir on the Georgia-South Carolina border. “I had seen eagle kills before in past events, but this was the reservoir where I had done my thesis research,” she says. “It was an interesting mystery but a success. That was the reservoir in which he had worked and had seen many eagles flying overhead. “

When Wilde had been collecting data for his dissertation in the mid-1990s, there was not much vegetation growing in the reservoir. But when he returned a few years later, the lake had been overtaken by an invasive plant called hydrilla, which is easy to grow and has become a popular plant for fish tanks. (Rumor has it that hydrilla was initially released in the US in the 1950s when it outgrew an aquarium and someone dumped it into a Florida canal. Since then, it has become one of the most pernicious aquatic weeds in the world. country, thriving in freshwater lakes Washington to Wisconsin to the Carolinas.) Wilde began to wonder if eagle kills and the presence of this new plant were related.

But Wilde had to question all possible suspects. He began by sampling the lake’s water and sediment in search of bacteria. She arrived empty-handed. But when he began examining the leaves of the hydrilla plant, he found colonies of a previously unknown cyanobacterium. She named him Aetokthonos hydrillicola, “The eagle killer that grows on hydrilla”.

Photograph: Getty Images

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