The Port of Tacoma’s dead gull mystery has been solved, partly.
Dozens of dead and paralyzed gulls found around the port earlier this year were the victims of a botulism outbreak, the state Department of Fish and Wildlife said Thursday.
Although testing at a federal lab in Wisconsin couldn’t pinpoint where the birds caught the botulism — as scavengers, their poisonous prey could have been rotting fish or old human-dumped food — the tests revealed the botulism was a strain not associated with human illness.
The finding provides as much of a definitive answer as officials hope to find about why the dead and paralyzed birds appeared around Commencement Bay.
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The birds came from two species of gulls, and no other animals appeared to be affected.
Port workers reported finding at least 30 dead and dying birds Jan. 22. By Feb. 5, a dozen more dead gulls had been reported by the public, and 31 sick birds had been taken to state-licensed wildlife rehabilitation centers.
Initial testing ruled out avian influenza, avian cholera and lead poisoning, according to the Fish and Wildlife report. No evidence of algae toxins or water contamination was found.
Whatever the source of the germ, the relatively small size and duration of the outbreak were clues it didn’t signify a mass problem, Fish and Wildlife veterinarian Katie Haman said.
“It was probably a really acute, really small source, basically,” she said, “because otherwise we would’ve seen it more widespread in more species and more gulls.”
The birds were sent for testing to a U.S. Geological Survey laboratory in Madison, Wisconsin, which found botulism was the shared culprit in a series of tests.
Had that failed, a more expensive round of molecular testing was set to take place at Washington State University, Haman said.
Although the outbreak appears to be over, state officials said anyone who sees a dead or injured gull should put on gloves before trying to help or move it.