A brevetoxin-specific ELISA was used to test environmental samples, and marine- and shorebirds displaying neurologic abnormalities during a prolonged red tide event in the Gulf of Mexico during 2005–2006.1 Histologic examinations were performed on select birds.
Results suggest that coquina clams (Donax variabilis) are efficient bio-accumulators of brevetoxin and may pose an exposure risk as a food source. Gastrointestinal contents of all species of birds examined frequently had high levels (>300 ng/g) of brevetoxin present, suggesting ingestion is a primary route of exposure. Highest tissue levels of toxin were most consistently found in gall bladder, followed by liver. Brevetoxin was also detected in kidney, lung, muscle, brain and/or heart in some birds. Brevetoxin was detected in serum or plasma at low levels (1–13 ng/ml) in multiple live birds.
Neurologic symptoms associated with suspected brevetoxicosis include ataxia, disorientation, hyperexcitability, ascending paralysis and loss of palpebral reflex. Symptoms appeared to be somewhat species specific. Gross necropsy findings frequently included cloacal impaction and/or emaciation. Pulmonary congestion was noted on gross and/or histologic examination of some birds; however, due to the low number of fresh carcasses examined, no definitive conclusions could be drawn.
The authors would like to thank the wildlife rehabilitators that have provided samples for this research, including Dr. P.J. Deitschel and C.R.O.W. staff, Lisa Miller, Mary Coerver, Amanda Wilkerson, Chris Beatty, Lloyd Brown and many others. We would also like to acknowledge diagnostic support from the Southeastern Cooperative Wildlife Disease Study, particularly Dr. John Fischer and Dr. Kevin Keel; Dr. Betty Miguel and her staff at Kissimmee Animal Diagnostic Lab, and the assistance of Dr. Mark Cunningham and Bambi Ferree of Florida Fish and Wildlife Conservation Commission. This research was supported in part by funds from the National Oceanic and Atmospheric Administration’s Coastal Management Program through the Florida Department of Environmental Protection and the Florida State Wildlife Grant Program.
1. Naar, J., A. Bourdelais, C. Tomas, J. Kubanek, P.L. Whitney, L. Flewelling, K. Steidinger, J. Lancaster, and D.G. Baden. 2002. A competitive ELISA to detect brevetoxins from Karenia brevis (ex. Gymnodinium beve) in seawater, shellfish, and mammalian body fluid. Env Health Persp. 110(2): 179–185.