Avian vacuolar myelinopathy linked to exotic aquatic plants and a novel cyanobacterial species.
Invasions of exotic species have created environmental havoc through competition and displacement of native plants and animals. The introduction of hydrilla (Hydrilla verticillata) into the United States in the 1960s has been detrimental to navigation, power generation, water intake, and water quality (McCann et al., 1996). Our field surveys and feeding studies have now implicated exotic hydrilla and associated epiphytic cyanobacterial species as a link to avian vacuolar myelinopathy (AVM), an emerging avian disease affecting herbivorous waterbirds and their avian predators. AVM, first reported in 1994, has caused the death of at least 100 bald eagles (Haliaeetus leucocephalus) and thousands of American coots (Fulica americana) at 11 sites from Texas to North Carolina (Thomas et al., 1998; Rocke et al., 2002). Our working hypothesis is that the agent of this disease is an uncharacterized neurotoxin produced by a novel cyanobacterial epiphyte of the order Stigonematales. This undescribed species covers up to 95% of the surface area of leaves in reservoirs where bird deaths have occurred from the disease. In addition, this species is rare or not found on hydrilla collected at sites where AVM disease has not been diagnosed. Laboratory feeding trials and a sentinel bird study using naturally occurring blooms of cyanobacteria on hydrilla leaves and farm-raised mallard ducks (Anas platyrhynchos) induced the disease experimentally. Since 1994 AVM has been diagnosed in additional sites from Texas to North Carolina. Specific site characteristics that produce the disjunct distribution of AVM are unknown, but it is probable that the incidence of this disease will increase with the introduction of hydrilla and associated cyanobacterial species into additional ponds, lakes, and reservoirs.
Wilde
Susan B
SB
Belle W. Baruch Institute for Marine and Coastal Sciences, University of South Carolina, Charleston, South Carolina 29412, USA. wildes@mrd.dnr.state.sc.us
Murphy
Thomas M
TM
Hope
Charlotte P
CP
Habrun
Sarah K
SK
Kempton
Jason
J
Birrenkott
Anna
A
Wiley
Faith
F
Bowerman
William W
WW
Lewitus
Alan J
AJ
D000818:Animals; D001427:Bacterial Toxins / Q000633:toxicity*; D001715:Bird Diseases / Q000453:epidemiology / Q000209:etiology*; D001717:Birds; D000458:Cyanobacteria / Q000472:pathogenicity*; D003625:Data Collection; D003711:Demyelinating Diseases / Q000453:epidemiology / Q000209:etiology / Q000662:veterinary*; D004196:Disease Outbreaks; D031321:Hydrocharitaceae / Q000254:growth & development / Q000382:microbiology*; D015994:Incidence; D009026:Mortality; D009186:Myelin Sheath / Q000473:pathology; D014481:United States / Q000453:epidemiology
D001427:Bacterial Toxins