Saturday, July 31, 2010

Wells Lake Rookery: Possible Botulism

On Friday morning, John H. and I canoed to the Wells Lake Rookery near Faribault in Rice County, Minnesota.
The majority of the birds present were Double-crested Cormorants.
We were careful not to overly disturb the birds so we did not disembark.  Many cormorants flew overhead.
Also nesting in the rookery were dozens of Great Egrets.
And a few Great Blue herons.
All, however, was not well at the rookery.  Dozens of cormorants were dying along the shore. They displayed the symptoms of avian botulism. This diagnosis should be confirmed through laboratory analysis of the carcasses.  Other species at the rookery did not seem to be affected.
According to the National Wildlife Health Center,, avian botulism is a paralytic disease caused by a toxin produced by the bacterium, Clostridium botulinum. The toxin affects the birds' nervous systems, leaving them unable to use their wings and legs, neck muscles (as in the photo above) and other muscles. Although we only saw a few dozen crippled or dead cormorants, avian bacteria can strike thousands of waterfowl at once.

Botulism comes in several strains.  Type C affects birds, mostly waterfowl, shorebirds, colonial waterbirds, and other species.  Humans, dogs, and cats are resistant to this strain.  Only a few cases are reported from people and their pets.  We have to worry about Types A, B, and, perhaps E.  A and B are contracted from eating improperly preserved canned products.  Type E is from poorly cooked fish, and affects gulls, loons, and other birds. Thorough cooking destroys all types of botulism, according to the National Wildlife Health Center.

John and I immediately reported this mini-outbreak to the Minnesota Department of Natural Resources. Outbreaks can be controlled by collecting and destroying carcasses and, if dealt with promptly,  through intervention by wildlife rescue organizations.

1 comment:

  1. These symptoms also hold for Newcastle's Disease. Newcastle's disease is viral and can be devastating to chicken flocks. According to the Minneapolis Tribune, Newcastle's Disease has been diagnosed in cormorant flocks in western Minnesota in August 2010.