Abstract

The aim of this study was to evaluate kinetics of meloxicam administration, in association to observed changes due to frequent handling and blood-sampling on hematology, plasma biochemistry and plasma protein electrophoresis (PPE) for large-spotted catsharks (Scyliorhinus stellaris) maintained under human care. To our knowledge, no baseline blood reference values have been established yet for this species. Additionally, interpretations of fish, and specifically elasmobranch hematological and plasma biochemical values under different physiological or clinical conditions are currently scarce but relevant indicators of health/welfare status.^1-5 Two different pharmacokinetic (PK) studies with meloxicam were performed on the same group of 8 animals with a resting period of 6 months between studies: first, meloxicam was administered intramuscularly (IM) at 0.5 mg/kg and then orally (PO) at 0.5 mg/kg. Both sampling routines were identical, and blood was collected via caudal vein at 15, 30, 60, 180, 360, 540, 720 and 1440 min post administration. There is currently only one published PK study performed with meloxicam in teleosts, and no studies have been yet published in elasmobranchs.⁶ However, meloxicam is frequently used in the clinical management of these animals.⁷ Our preliminary results show important variations in absorption between enteral and parenteral administration routes. Oral administration did not produce any detectable meloxicam levels in blood plasma in any of the collected samples, while same dose of meloxicam IM was detected in plasma from 15 to 1440 min after administration.

Both PK studies required intensive handling with frequent capture, immobilization, and sampling. Reference samples to evaluate handling impact on each group included one prior to intensive handling and the last one at the end of the PK study. Marked differences were found in some hematology, plasma biochemistry and PPE values before and after intensive handling. Significantly higher mean values (p<0.05) after manipulation compared to the values obtained prior to the manipulation and meloxicam administration were found for heterophil total count, creatine kinase (CK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and total protein (TP) values for the animals which were injected with meloxicam intramuscularly and for CK and TP for the animals which received oral medication. Catsharks plasma protein electropherogram was analogous to other elasmobranch PPE profiles and was divided into five fractions for its evaluation.^6-8 In the group treated IM, different fractions of the electropherogram also showed significant changes at the end of the study. These electrophoretic changes as well as the increase in AST and LDH average values were not observed or were not significant in the animals administered orally reflecting consequences of post injection tissue damage or metabolic effects of the drug. Consistent rise in CK and TP in both groups was considered direct consequence of handling stress as drug absorption was negligible through the PO route. Fish welfare is an increasingly important concern and minimizing environmental stress has proven effective at reducing fish disease.¹⁰ Besides the PK work, different parameters were found relevant indicators when it comes to evaluate the impact of handling on the inflammatory and enzyme activity response in elasmobranchs.

Acknowledgements

The authors thank the husbandry and animal care staff from Oceanogràfic of Valencia for their dedicated care of the different animal species at the Aquarium and the veterinary team for their help and support.

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