May 15, 2021

A new species of toxic blue-green algae has been identified as the cause of a neurologic disease that has been killing bald eagles and other animals in the southeastern United States for more than 25 years.

In a study published in Science on March 26, researchers from the University of Georgia and their international partners describe a new cyanobacterial species—Aetokthonos hydrillicola—growing on the leaves of an invasive water plant, Hydrilla verticillata, in human-made lakes when bromide is present.

Of the thousands of known cyanobacterial species, approximately 200 are known to be toxigenic, according to Greg Boyer, PhD, director of the Great Lakes Research Consortium and a professor of biochemistry at State University of New York. Those toxigenic species also happen to be among the most common.

Authors of the Science article noted that the algae-bromide combination they investigated produces a neurotoxin that causes avian vacuolar myelinopathy, a neurologic disease first diagnosed in 1994 in bald eagles. In addition to water fowl and birds of prey, vacuolar myelinopathy also affects amphibians, reptiles, and fish.

For decades, the cause of the disease had eluded researchers, but field and laboratory studies demonstrated that the neurotoxin that causes vacuolar myelinopathy can be transferred through the food chain, from herbivorous wildlife to birds of prey.

While vacuolar myelinopathy has not been seen in humans, the newly identified cyanobacteria and animal deaths from the disease have been documented in watersheds across the southeastern United States, leading researchers to encourage people to know the signs of infection in animals and avoid consuming them.

“We want people to recognize it before taking birds or fish from these lakes,” said Susan Wilde, PhD, an associate professor of aquatic science at the UGA Warnell School of Forestry and Natural Resources who discovered the cyanobacteria, in a statement.

In some animals, such as birds, turtles, and beavers, the disease manifests as erratic movements or convulsions.

“For fish, it’s tough. I would avoid eating fish with lesions or some sort of deformities; we do see affected fish with slow swimming speeds, but anglers won’t be able to see that,” Dr. Wilde said. “We want people to know the lakes where this disease has been documented and to use caution in consuming birds and fish from these lakes.”