After eluding scientists for more than 25 years, the cause of vacuolar myelinopathy, a fatal neurological disease that affects waterbirds and raptors, has finally been revealed - a new cyanobacterial neurotoxin called aetokthonotoxin. In their study, the researchers illuminate an unexpected nexus that gave rise to this novel toxin: it is produced by a relatively newly identified cyanobacterial species - one commonly found dominating invasive water plants - when that cyanobacterial species is exposed to anthropogenic bromide in the environment. The insidious combination not only causes lethal neuropathy in the animals that eat the cyanobacteria-colonized plants, but it also bioaccumulates, killing their predators as well. Avian vacuolar myelinopathy (AVN) was first discovered during a mysterious mass mortality event of bald eagles in Arkansas during the winter of 1994-95. In the decades since, the disease has been observed in a number of bird species, and its occurrence has continued to spread throughout freshwater reservoirs of the southeastern United States. While previous research has linked AVN to the consumption of the cyanobacterium Aetokthonos hydrillicola, which colonizes aquatic plants, particularly the highly invasive hydrilla, the diseases' causative agent has remained at large. Since cyanobacteria are often associated with the production of toxins, Steffan Breinlinger and colleagues closely evaluated the role of A. hydrillicola in AVN. Breinlinger et al. discovered that the colonization of waterways by the invasive plants provided a substrate for growth of the relatively newly identified cyanobacterium. They also found that it is only after exposure of the cyanobacterium to environmental bromide, largely anthropogenic in origin, that AVN-causing cyanobacterial neurotoxin, aetokthonotoxin is produced. "A toxin produced by cyanobacteria that colonize a highly invasive plant, which has the capacity to affect diverse animal phyla, should not be underestimated in its potential impact on our environment," write Breinlinger et al. "Moreover, there remains a critical need for research on mammalian susceptibility to VM and on human health risks from consumption of fish and waterbirds from VM reservoirs."
###
Journal
Science