Abstract

Two southern stingrays (Dasyatis americana) housed in a large multispecies tank at Atlantis resort in the Bahamas died within 11 days of each other and 14 days post Hurricane Sandy. Both southern stingrays were behaviorally normal prior to storm event. Upon necropsy, one ray was found to have two and a half intact oleander (Nerium oleander - family Apocynaceae) leaves located in the stomach. The only histologic finding was multifocal epicardial hemorrhage. The second ray died in a quarantine pool after removal from main lagoon habitat 11 days after initial presentation of neurologic behavior such as; disorientation, erratic swimming patterns, blood from vent, lethargy, inappetance and tremors. Upon necropsy, olive green digesta and very small foliage pieces were found in the gastrointestinal tract but no intact vegetation. Histologically hepatic lipid stores were decreased, consistent with the history of prolonged anorexia. There were no other histologic lesions. The presence of ingested oleander leaves in the first case coupled with suggestive lesions of epicardial hemorrhage, suggests sublethal oleander toxicosis. In the second case, neurologic signs were also consistent with (sublethal) toxicosis; supported by proximity to the other stingray mortality as well as the lack of overt evidence of other potential causes. Anorexia was presumably the cause of death but was also considered secondary to initial neurologic signs. It is possible that if there was oleander ingestion, after 11 days of quarantine clinical treatment, any vegetation could have been broken down and possibly expelled.

All parts of Oleander species are poisonous to animals and humans and have been used to formulate fish pesticides (piscicide). Digotoxin is the main neurotoxin associated with oleander toxicity and has cardiac glycoside properties. Neurologic conditions from oleander toxicity include uncoordinated gait, disorientation, and tremors/seizures. Gastrointestinal signs can include diarrhea and bleeding. The facility lagoons holding animals are open and can allow for accumulation of storm blown debris. There are large groves of oleander located around the facility's property as it is a commonly used ornamental plant for landscaping. While it is not always common to have oleander directly next to the lagoon pools, during storm and high wind events, foliage can be brought in contact with the pools in which the fish are housed. Due to the risk of lethal ingestion of oleander by fish, it would be highly recommended that oleander not be a part of a landscaping plan in habitats with direct outside access.

Acknowledgements

The authors would like to acknowledge Michael Kinsel of the University of Illinois Zoological Pathology Program, Michelle Liu and the Atlantis Marine Aquarium Operations (MAO) team for their continued cooperation on aquarium clinical cases and the Dolphin Cay laboratory assistants.

* Presenting author