Abstract

An adult male bottlenose dolphin was found to have elevated blood lead concentrations in July of 1997. The dolphin did not demonstrate clinical signs consistent with lead intoxication at this time or throughout the six-month period of during which the animal had elevated blood lead levels. Radiographs showed the presence of metallic objects in the dolphin's gastrointestinal tract. A combination of medical therapy, gastric lavage, and endoscopic retrieval was used to remove the lead material from the stomach. Blood lead levels returned to normal after treatment was complete.

The affected dolphin is held at The Living Seas Pavilion at Epcot® in a six million-gallon water system. During routine oral examination, two small (1-3mm) pieces of metal were noted to be loosely embedded in the gingival mucosa. The metal was identified as lead. Further investigations revealed that a weight belt had probably spilled lead pellets into the system. Radiographs of the gastric and oral regions showed numerous radio-opaque densities in the area of the first gastric compartment. Blood lead levels at this time were markedly elevated (92 mcg/dl). Other blood parameters were unremarkable and the dolphin was clinically normal.

Chelation therapy was initiated with succimer (dimercaptosuccinic acid); an oral medication recently approved for use in humans as a heavy metal chelator. Succimer forms water-soluble chelates with lead, allowing enhanced urinary excretion of the metal. Lead is stored in bone and a rebound effect is commonly seen after succimer is withdrawn as lead is redistributed from bone stores to soft tissue and blood. Lead toxicity in humans is treated with pulse therapy. Chelation is followed by several weeks without therapy to allow lead to move from bone stores into blood. From July to December, the dolphin was treated with nine cycles of succimer therapy. Using doses extrapolated from human data, the dolphin received 600 mg PO BID for 5 to 7 days. Serial blood samples revealed a peak blood lead concentration (154 mcg/dl) in August of 1997 and a steady decline until March of 1998. The dolphin remains clinically normal with blood lead concentrations less than 10 mcg/dl for the last 12 months. Other oral medications that were intermittently used during this time included psyllium, mineral oil, sucralfate, nystatin and enrofloxacin.

Endoscopy and gastric lavage were used to remove the lead material from the stomach. A small mesh net was adapted for retrieval of the pellets using an endoscope. Lead pellets were also successfully removed via gastric lavage. Two large equine stomach tubes were placed into the first gastric compartment. One tube was used to pump water into the stomach and the other allowed the water and pellets to drain out by gravity flow.

Manual and electric water pumps were used to instill water into the stomach. Attempts to remove the pellets using suction met with variable success.

Blood sampling and radiographs were usually obtained as conditioned behaviors or during short periods of manual restraint. The more invasive procedures were performed after the animal had been removed from the water. Chemical sedation with midazolam HCl (15 mg IM) was used for endoscopic procedures and for gastric lavage with good results. After the procedures were completed the effects of midazolam were antagonized using flumazenil (0.5 mg IM). The dolphin was sedated five times during the treatment period with no complications noted during these events.

Acknowledgements

The authors are indebted to the veterinary staff at SeaWorld of Florida for their extensive help in this case including numerous consultations and repeated technical assistance. We would also like to thank the marine mammal trainers at the Living Seas for their help and support.