National Wildlife Health Center

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Avian Vacuolar Myelinopathy - FAQ

What is the cause of AVM?
The exact cause of AVM is not known. Diagnostic, laboratory and field work suggest a toxin, either naturally occurring or man-made. Tests for a variety of compounds, including some known to cause vacuolar myelinopathy, have been negative to date.There is no evidence of bacterial, viral or parasitic infection.

Is AVM a prion disease like bovine spongiform encephalopathy?
It is not currently thought that AVM is a prion disease based on laboratory testing, the lesion itself, and consultation with prion disease experts.

How are the birds exposed to AVM?
The exact route of exposure or intoxication is not known. It could be that eagles develop AVM after ingesting affected coots or waterfowl, however all the species affected may come in contact with the same disease agent independently of each other.

What species have been confirmed with AVM

  • Bald eagles
  • American coots
  • Waterfowl
  • Other - killdeer, great horned owl

What are the clinical signs?
Affected birds may have wobbly or uncoordinated flight and may crash land. Eagles have been observed to fly into objects such as rock walls. On land, birds are unsteady, walk with wings outstretched and appear "intoxicated". In the water, coots and waterfowl have been observed swimming upside down, or trailing a wing or leg. In general, affected birds are alert and aware of their surroundings.

When does the disease occur?
AVM typically occurs between November and March, which is generally when the overwintering avian populations migrate into and out of the area.

Where has this disease occurred?
As per diagnostic and research work conducted by USGS and SCWDS:
Arkansas - Lakes De Gray, Ouachita, Hamilton and Greeson - within approximately a 35 mile area of southwestern Arkansas.
Georgia - Lake Juliette (near Macon) and Strom Thurmond Lake (on Georgia/South Carolina border)
North Carolina - Woodlake near the town of Vass
South Carolina - L Lake and Par Pond on Savannah River Ecology Lab, Lake Murray (near Columbia)
Texas - Suspect cases occurred on Sam Rayburn Reservoir (in eastern Texas near Nacogdoches)


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Page Last Modified: Jun 20, 2018