Avian Cholera may be cause of bird deaths

The recent rash of bird deaths in Richardson Bay may be avian cholera. The first necrospy done on three birds showed that one bird died of this highly contagious bacteria. The disease is commonly transmitted through contact with secretions or feces of infected birds or the ingestion of food or water containing the bacteria.

According to the California Fish and Games website: "Avian cholera (not related to human cholera) is a common disease of North American waterfowl and results from infection with the bacterium Pasturella multocida. It spreads rapidly from bird-to-bird and can kill thousands of birds in a single incident. A bird infected with avian cholera dies quickly. Avian cholera die-offs in waterfowl commonly occur during the winter months in California, especially during cold spells and fog."

At least 235 birds were picked up dead over the past two weeks. The spike was blamed on two recent sewage spills into the bay. At least 5 million gallons of partially treated human waste was dumped from the Marin County area. Scientists believe that the spill may have contributed to the rise of avian cholera. More tests on some of the other dead birds will help researchers determine the true cause.

See the San Francisco Chronicle story: Cholera killed bird found in Richardson Bay

What's killing the birds in Richardson Bay?

At least 160 birds have turned up dead along the shores in Richardson Bay near Tiburon and UC Davis scientists are expected to report this week on what caused the deaths.

The birds certainly could have been affected by two recent sewage spills in Marin County that dumped nearly 5.5 million gallons of partially treated sewage into the northern part of San Francisco Bay. Those spills occurred on January 26 and 31. The birds started appearing shortly thereafter.

The Richardson Bay Audubon Center and Sanctuary in Tiburon reported an unusual number of dead birds following the spills. There was also speculation that these birds could have also been suffering from remnants of the Cosco Busan oil spill that hit the bay on November 7, 2007.

Media reports:

Alarming spike in Richardson Bay bird deaths, San Francisco Chronicle

Necropsy Results On Dead Birds Due This Week, NBC-TV 11

Bird toll mounts on Richardson Bay, Marin IJ