Botulism caused the deaths of at least 30 gulls last month, according to final test results received by the Washington Department of Fish and Wildlife.
In a release, they say that the botulism detected was a toxin that is not associated with disease in humans, according to the report from the U.S. Geological Survey’s National Wildlife Health Center. Other lab tests for viruses, heavy metals, organophosphates, and other bacteria were negative.
Earlier tests had ruled out avian influenza virus, avian cholera, and lead poisoning. No other animals were affected and no evidence of water pollution or contamination was found. Although results are still pending from tests for marine algal toxins at a National Oceanic and Atmospheric Administration (NOAA) lab, the lack of other affected species indicates harmful algal blooms were not involved.
WDFW veterinarian Dr. Katie Haman and WDFW wildlife biologist Emily Butler, who led the investigation, said the gulls may have picked up the botulism toxin when scavenging in the area.
“Botulism is a bacteria frequently associated with fish kills and decaying carcasses that gulls often scavenge,” Haman said. “We’ll never know for sure what the gulls ate that caused the botulism toxicity, but since a limited number were impacted, it looks like it was a localized event.”
Although no further gull deaths or sickness have been reported this month, Haman said people should not handle birds without protective gloves and should keep dogs and other pets from scavenging bird carcasses.
Port of Tacoma workers reported on Jan. 22 that at least 30 gulls were found dead or dying in and around Commencement Bay. At least a dozen more dead gulls were reported by the public through Feb. 5, and 31 sick gulls showing signs of weakness and/or paralysis were taken to state-licensed wildlife rehabilitation centers.
Twenty-five of the 31 sick gulls were taken to the Progressive Animal Welfare Society (PAWS) in Lynnwood. Other gulls went to Puget Sound WildCare, Fair Isle Animal Clinic, and West Sound Wildlife Shelter. Sixteen of the gulls at PAWS and one at Puget Sound WildCare recovered and were released. Two gulls at West Sound Wildlife Shelter are doing well and will be released soon.