The bacterial neurotoxin is responsible for the fact that bald eagles die again and again in many US states. This has now been proven by researchers at the University of Halle-Wittenberg and the University of Georgia. Like her Report in “Science” magazine, Bacteria grow on a specific aquatic plant. However, it is possible that they only produce the toxin when the plant is controlled with herbicides.
In the winter of 1994, bald eagles first died on Lake DeGray in Arkansas from a then-unknown disease. Initially, the birds experienced tremendous movement disorders: they flew into the trees or crashed; They eventually died. Analyzes of her brain tissue showed that many fluid-filled vesicles formed in the insulating layer of the nerve tracts, the myelin, which destroyed the nervous system. The new disease has been called vacuolar myelopathy (VM).
In the years that followed, animals that died from the VM – including other bird species as well as reptiles, amphibians, and fish – were found near water in several states. It was noticed that all the affected lakes were infested with an invasive aquatic plant, the nettle. The nettles themselves were also colonized by unknown cyanobacteria at the time.
Since cyanobacteria were known to produce toxins, the team around Timo Niedermeier and Susan Wilde suspected that the neurotoxin was the cause of the disease. During a close microbiological examination of the colonized leaves, they discover a substance containing bromine, and they think it is the toxin they are looking for. Cyanobacteria also formed the unknown molecule in a petri dish if grown in a nutrient medium containing bromine. In order to see if the substance actually masked the toxin they were looking for, they tested its effect on chickens: this brain damage was typical of a VM over a short period of time, confirming the scientists’ skepticism.
The unusual thing is that bacteria need the bromine to produce the toxin – and you find it on the leaves of nettle. Why the chemical element accumulates there is not clear. It can come from power or fuel plants. Above all, however, the team around Niedermeier and Wilde suspected an herbicide containing bromine that is used to control nettle. Grass carp that naturally eat aquatic plants can contain invasive species. However, it is not very popular with fishery authorities, as there is a risk that large numbers of carp will become a problem for the lakes themselves. It should be noted if the neurotoxin can also be dangerous for people who drink contaminated water.