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The national emblem and mascot of the United States, the bald eagle, has been the target of a mysterious neurodegenerative disease for 25 years.
Researchers have been “researching” since 1994, according to a report from Live Science, when the disease, known as vacuolar myelinopathy (VM), was first discovered. At this time, a large number of bald eagle carcasses were found near Lake DeGray, Arkansas.
According to the researchers, an infected animal will begin to have motor function problems when VM attacks the brain, and eventually the animal succumbs to a “horrible death.”
Live Science quoted co-author Susan Wilde, a University of Georgia aquatic scientist who has studied VM since 2001, and told them, “When birds are really sick, they just look really drunk. stumble and fall. She added: “But it’s even worse, they are paralyzed, blinded and may have tremors and convulsions before finally succumbing to the disease.”
Scientists had no idea how the disease was contracted.
Initially, scientists had no explanation for how the eagles contracted the disease. Eventually, they “identified an invasive plant and later a particular species of cyanobacteria that appeared to be responsible,” but were unable to determine “the exact mechanisms” behind VM.
But, Live Science reports that a new study has found that “a neurotoxin called etokthonotoxin which is produced under certain circumstances by cyanobacteria living on invading plants” is the culprit.
Lead author Steffen Breinlinger, a doctoral student at Martin Luther University in Halle-Wittenberg, Germany, told Live Science: “A toxin produced by cyanobacteria that colonize a highly invasive plant, which has the ability to affect various phyla animals, should not be underestimated in its potential impact on our environment, ”the report quoted.
What is VM?
VM has spread rapidly in American lakes since its first discovery in 1994, the report notes.
“We’ve found it in nine states, from Virginia to Texas,” Wilde said. “But I don’t think we understand how many places this could be happening.”
Although a wide range of lake species, such as “fish, frogs, snails, salamanders, turtles and snakes, as well as small birds such as coots, owls and waterfowl” also appear being affected by the disease, “bald eagles are one of the most affected species because they feed on all of these other infected animals,” said Wilde.
“We know that at least 130 eagles have died testing VM-positive,” added Wilde. “But the cadaver recovery rate is probably around 10 or 12 percent, so it’s probably at least 10 times that number.”
To test for VM, researchers perform an autopsy immediately after the animal’s death. According to Wilde, “the only physical evidence of the disease” is “lesions and lesions of the brain,” which “can only be correctly identified for a short period of time after death”, which makes it possible to “follow the disease and to estimate deaths ”. more difficult, the quoted report.
Unravel the mystery.
Although early on, scientists discovered that VM “was only found in lakes where an invasive plant species, Hydrilla verticillata, was also found,” it soon became apparent that “all lakes where Hydrilla shoots weren’t related to VM ”, so it had to be something else that was causing the disease.
Then, in a new study by Wilde and colleagues in 2015, a species of cyanobacteria (Aetokthonos hydrillicola) was identified, which “has been found on Hydrilla in lakes where VM occurs in animals.” But the team still couldn’t explain how the bacteria were causing VM, the report noted.
In the new study, when Wilde sent samples of cyanobacteria to Breinlinger and other researchers in Germany, who attempted to grow bacteria cultures to see what toxins they produced, the German team found out to their dismay surprise that “the cyanobacteria grown in regular cultures produced no toxins and seemed to refute Wilde’s theory that they were responsible for VM.”
But, according to the report, when grown on crops containing bromide, “the plants produce a toxin that researchers now believe to be the cause of VM, called etokthonotoxin.” The translation of the name is “poison that kills the eagle”.
It is still not clear why the cyanobacteria produce the toxin and only do so in the presence of bromide, the researchers say. And, although bromide is naturally present in lakes in small doses, Breinlinger said it is also spread through “anthropogenic influence,” the use of herbicides and “chemical runoff from flame retardants and fire retardants. pollution from coal-fired power stations ”.
According to Wilde, the probability that VM will one day be eradicated from American lakes, “is highly improbable.” However, scientists now have a better understanding of the toxin responsible for it, which will help develop ways to “control the spread and manage the disease.”
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