Avian Cholera on the Chesapeake

March 06, 1994

The plague of avian cholera that has swept down the Chesapeake Bay this winter reminds us of the perplexing factors that nature periodically employs to regulate the ecosystem.

Scientists admit to helplessness in the wake of the rapid contagion that has killed thousands of ducks from Queen Anne's County through Virginia's portion of the bay. Department of Natural Resources workers can do no more than promptly retrieve the carcasses to keep the disease from spreading into the streams, rivers and ponds that could infect other birds, from sparrows to swans.

The bacterium, which zoologists believe is found in minute quantities in many birds and animals, poses a remote threat to Eastern Shore commercial poultry flocks and more directly to endangered species such as the bald eagle if it is not contained.

The biggest danger may be from infected sea gulls, which can carry the disease inland. But previous outbreaks of avian cholera in the Chesapeake region in 1970, 1975 and 1978 did not extend much beyond wild birds, although killing tens of thousands of waterfowl before disappearing.

The disease is thought to be triggered by the stress of icy winter conditions, when sea birds crowd together to feed, and then transmitted to healthy birds through tainted water and food. Scientists have no firm link to other causes. But there is no warning until its lethal effects are seen. Infected birds typically die within hours of the first symptoms.

Humans are not at great risk from the disease. But household pets can become sick if they have contact with infected carcasses. Experts caution that humans should use plastic gloves when handling dead ducks, pick them up by the bill and seal them in double plastic bags before burning or burying the remains. Exposed clothing and footwear should be disinfected with bleach solution.

"In some ways we feel helpless, but this is one of those things that occurs to our birds now and then," said Larry Hindman, Maryland's migratory birds program manager, who has been leading the cleanup. Adds Virginia waterfowl specialist Gary Costanzo: "We'll just have to let nature run its course."

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