Who is the killer of the bald eagle?
Biologists in Arkansas started reporting scores of paralyzed, convulsing, or dead bald eagles more than 25 years ago. Their brains were riddled with lesions never before seen in eagles. The disease was quickly discovered in other birds in the southeastern United States.
The birds had died from a disease called avian vacuolar myelinopathy (AVM) that attacks their brains, causing them to fly erratically or swim in circles before succumbing. Now, almost two decades later, scientists finally know what causes it.
Niedermeyer’s lab discovered the neurotoxin was fat-soluble, which is unusual for cyanobacterial toxins and suggests it can accumulate in tissues. Fish and birds are exposed when they eat hydrilla coated with the new species of cyanobacteria, and then the toxin may move through the food web as eagles and owls consume afflicted prey.
It all begins with Hydrilla verticillata, also known as waterthyme, an invasive species that was introduced to the United States in the 1960s after home aquariums were spilled into local waterways. This plant is a particularly appealing host for cyanobacteria such as Aetokthonos hydrillicola, and is not fatal to waterbirds on its own.
When these cyanobacteria are exposed to bromide, they develop a toxic neurotoxin known as aetokthonotoxin. According to the latest study, this is the toxin that triggers AVM within a bird’s body.