Abstract

A mass mortality event of wild and captive sea stars has resulted in the loss of millions of individuals along the western coast of North America.¹ A virus has been associated with the disease termed Sea Star Wasting Disease (SSWD); however, no definitive etiology has been identified.² The purple sea star (Pisaster ochraceus) is a predominant intertidal species and is commonly affected.³ Anecdotal reports of treating affected aquarium animals with antibiotics indicate varied success; enrofloxacin is one of the commonly used agents. Although antibiotic pharmacokinetic studies have been performed in other invertebrates, pharmacokinetic data for echinoderms are lacking.^4,5 This study investigates enrofloxacin pharmacokinetics by intracoelomic injection and immersion treatment in P. ochraceus.

Twelve study individuals and two control animals were utilized for each method of administration - a single 5 mg/kg intracoelomic injection or 5 mg/L 6-hr immersion. Water vascular system samples were obtained hourly during immersion and at various times over a 120-hr period following enrofloxacin administration. No adverse effects to treatment or repeated sampling were observed. Drug concentration in the samples was assayed using HPLC to derive pharmacokinetic parameters.

For the intracoelomic injection, elimination half-life (t_1/2), peak concentration (C_max), and area under the curve to infinity (AUC_0-∞) were respectively 43.7 hr, 22.1 µg/mL, and 370.1 hr*µg/mL. After 6 hr immersion, t_1/2, C_max, and AUC_0-∞ were 92.8 hr, 0.67 µg/mL, and 39.7 hr*µg/mL, respectively. The immersion route resulted in 10% relative exposure compared to the injection. These results are valuable for echinoderm antimicrobial therapy and future related work.

Acknowledgements

The authors thank Shannon Balfry, Dave Carlson, and Boaz Hung for their support with housing and caring for the animals used in this study. The authors also thank Danny Kent and the BC Waters Aquarists at the Vancouver Aquarium for acquiring the animals under Department of Fisheries and Oceans Canada permit XR 1 2014. A debt of gratitude is also owed to Delta Dise for her help in processing the samples for analysis. This project was funded through a Boeing private grant for sea star wasting disease related research through the Seattle Aquarium.

* Presenting author
⁺ Student presenter

Literature Cited

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2.  Hewson I, Button JB, Gudenkauf BM, et al. Densovirus associated with sea-star wasting disease and mass mortality. In: Proc Natl Acad Sci USA. 2014;11(48):17278–17283. doi: 10.1073/pnas.1416625111.

3.  Sea star wasting syndrome: status of the science and identification of response actions. Newport, OR: Oregon State University; June 29–30, 2014.

4.  Gore SR, Harms CA, Kukanich B, Forsythe J, Lewbart GA, Papich MG. Enrofloxacin pharmacokinetics in European cuttlefish, Sepia officinalis, after a single i.v. injection and bath administration. J Vet Pharmacol Ther. 2005;28:433–439.

5.  Nolan MW, Smith SA, Jones D. Pharmacokinetics of oxytetracycline in the American horseshoe crab, Limulus polyphemus. J Vet Pharmacol Ther. 2007;30:451–455.