Abstract

Beginning in early August 2012, increased numbers of mostly waterfowl and shorebirds were reported sick or dead on the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island, Maryland. An avian botulism event was suspected, but initial testing came back negative and the freshwater algal toxin microcystin was detected in the water. This naturally-occurring toxin causes acute liver damage and death.

Blood, liver, gastrointestinal contents, and water samples were submitted for analysis by LC/MS. One blood sample was negative for microcystin and the additional freshwater algal toxins anatoxin and nodularin. Twelve of fifteen liver samples were positive for microcystin at levels consistent with or exceeding those associated with other reported bird and mammalian mortalities in the United States. One water sample and five of seven samples of gastrointestinal contents were also positive for microcystin.

Mortalities began to taper off in mid-September and had subsided by the first week of November 2012. Over the course of the 14-week event the total number of individual animals collected was 777: 564 dead (556 birds and 8 mammals) and 213 live, representing 35 different species. The survival rate for birds admitted for rehabilitation and surviving initial stabilization and treatment was 56%. Avian botulism was later confirmed in additional bird carcasses submitted for diagnostics and was responsible, in some part, for some of the mortalities observed during the mortality event.

Acknowledgements

The authors wish to thank the staff and volunteers at Tri-State Bird Rescue and Research, Inc., (TSBRR) for making all those trips to Tilghman Island and receiving sick birds for transport to TSBRR. Thanks to all the volunteers who took time from their regular jobs to assist in field surveys collecting sick and dead birds and made it possible to conduct thorough and efficient field surveys. Thanks to the staff at the Southeastern Cooperative Wildlife Disease Study, National Wildlife Health Center, and University California-Davis for pathology and diagnostics of submitted wildlife. The training provided by Dr. Cindy Driscoll of the Maryland Department of Natural Resources to Maryland Environmental Service (MES) staff on how to stabilize sick birds before being transported to TSBRR is greatly appreciated. A very special thanks to MES Environmental Unit staff Michelle Osborne, Claire Ewing, and Alexa Poynter for their field assistance in collecting sick and dead birds on a daily basis, stabilizing sick birds, and making it possible to get sick birds to TSBRR as quickly as possible. Lastly, thanks to Chris Dwyer and the U.S Fish and Wildlife Service's Region 5 Office of Migratory Birds for providing funding for pathology and diagnostics of individual animals and chemical analyses of tissue samples.

* Presenting author