Abstract
Cownose rays (Rhinoptera bonasus) are medium-sized elasmobranchs commonly kept in aquaria throughout North America. Eimeria southwelli, an apicomplexan parasite, is a known organism associated with mortality in cownose rays.1 Clinical signs of Eimeria infection include discoloration, emaciation and death.1 An adult female cownose ray housed in captivity long term, but initially wild caught, was maintained in a large, approximately 510,300-L multi-species exhibit. At initial clinical presentation, this ray was observed to be severely emaciated (weight 1.36 kg) and discolored. The animal was manually captured and medically evaluated. A coelomic cavity saline flush and sampling with cytological concentration was performed, and E. southwelli oocysts were observed on microscopic evaluation of the fluid. The animal was subsequently placed into an isolated established system approximately 1,810 L for further medical observation and treatment.
The animal was treated with a one-time dose of copper wire particles (50 mg, Copasure®, Animax Ltd, Shepards Grove West Stanton, Bury St. Edmunds, Suffolk, IP31 2AR, England) at a dosage of 36.7 mg/kg. The copper wire particles were placed in an empty dosing gel capsule and fed orally with frozen-thawed diet items. The animal was monitored daily and fed a varied diet consisting of shrimp, silversides, squid and pelleted food until satiation twice daily. Weights were obtained weekly, and coelomic cavity saline flush and sampling were performed at 6 and 10 weeks post copper wire treatment to observe for E. southwelli oocysts; both were negative for visible oocysts. At week 10, the animal had returned to a normal body condition, normal activity level, and was over 2 kg and determined to be clinically normal and returned to the main exhibit, where it remains. Coelomic cavity saline flush and sampling are one of the most common and effective ways to diagnose E. southwelli in cownose rays;1 however, it is not a sensitive test for detection. Copper-related treatments are not commonly used in elasmobranch species. In the case of this particular cownose ray, copper wire particles given orally appeared to be a safe and effective treatment option for an E. southwelli infection. Future studies evaluating the pharmacokinetic and dynamic effects and safety of this treatment in cownose rays are indicated.
Acknowledgements
The authors thank the husbandry and life support staff of the Audubon Aquarium of the Americas for their technical assistance.
* Presenting author
Literature Cited
1. Stamper MA, Lewbart GA, Barrington PR, Harms CA, Geoly F, Stoskopf MK. Eimeria southwelli infection associated with high mortality of cownose rays. J Aquat Anim. 1998;10:264–270.