San Diego

An outbreak of bird botulism caused public health officials to shut the Lake Murray water supply Saturday.

Though the disease is not believed to be transmittable to humans through water, the supply to the lake’s drinking water filtration plant was closed as a precautionary measure, said Tom Gallagher, a county Department of Health Services spokesman.

About 100 ducks, pigeons and other birds have died at the lake since Friday, Gallagher said. A preliminary investigation by county veterinarian Kerry Mahoney determined that the die-off was most likely caused by botulism, which was spread through maggots that accumulated around the carcasses of the birds, Gallagher said.

Testing of the water will continue, but there is no evidence of a health threat to the public, he said. Customers also will continue to receive their regular supply of water.

Lake Murray will remain open for recreational uses.