Abstract

Decompression sickness (DCS) as a clinical diagnosis has been recently recognized as a new pathologic entity in sea turtles. Our main goal is to provide the basics to maximize diagnostic and therapeutic capabilities in all potentially affected animals.

Until now, this condition has been only detected in animals forcibly submerged coming from by-catch interactions. Some necropsy findings in dead stranded sea turtles, though highly compatible with the condition, could not be fully confirmed to be consequence of DCS due to putrefaction interference. Systematic evaluation of DCS compatible signs in bycaught animals from trawlers and gillnets (n = 85), has revealed a relatively high prevalence of disease (48%).

Diagnostic imaging is the most reliable approach for gas embolism confirmation, including common and relatively affordable veterinary techniques, such as radiography or ultrasonography. The most consistent diagnostic regions to explore for a quick evaluation are kidneys, heart and liver, showing different degree of intravascular gas accumulation depending on severity.

Careful dissection of deceased individuals could permit the pathologists to directly visualize the presence of gas in certain key anatomical regions including right atrium, sinus venosus, mesenteric veins, and postcava vein. However, in less severe cases it is rather complicated to visualize gas on necropsy. Other gross lesions such as congestive/hemorrhagic areas in the kidneys, liver, and/or in the intestinal mucosa, are also commonly present in many cases of decompression. On histology, intravascular gas bubbles associated with general congestion and perivascular hemorrhages in selected tissues represent the main findings.

According to our experience, disease outcome greatly depends on total amount and distribution of intravascular gas, time to hyperbaric oxygen therapy (HBOT), severity of clinical signs and evidence of pulmonary water aspiration. Adapted human diver's recompression-decompression tables had been progressively readjusted with time towards longer treatment regimes for turtles. The condition is generally lethal in moderate and severe cases not receiving HBOT and could cause sequelae in patients, even in mild cases. Kidney ischemic lesions were observed through magnetic resonance images, necropsy and histopathology in late/non-treated individuals several days after gas reabsorption and blood profile normalization, indicating a temporal and potentially permanent loss of renal functional capacity. Permanent neurologic damage has been also associated with late HBOT-treated mild embolism. Therefore, we consider all professionals dealing with bycaught or forcedly submerged sea turtles should be familiar with these diagnostic and therapeutic techniques in order to minimize sea turtle mortality or any other risks associated with organic damage in survivors.

Based on these preliminary findings, the present recommendation would be to apply HBOT as soon as possible in any sea turtle with confirmed gas embolism to decrease mortality and risk of potential permanent damage. Besides DCS treatment and based on the experiences with other species, we also consider HBOT could be an additional interesting tool for the sea turtle practitioner to treat other common conditions affecting these animals such as certain ischemic lesions, non-healing wounds, refractory osteomyelitis, severe blood loss, intracranial abscesses, necrotizing soft-tissue infections, CNS trauma or other hypoxic conditions.

Acknowledgements

We thank all professionals at the Oceanografic, especially at the ARCA Rehabilitation Centre, for their many efforts and complete dedication to the best animal care. We are also grateful to the Consellería de Infraestructuras, Territorio y Medio Ambiente of the Valencia Community Regional Government who made the project possible with their support. We finally want to thank all the professionals involved with the Experimental Radiology Platform at the Hospital la Fe de Valencia and the GIBI230 group for their invaluable assistance in image acquisition and post-processing.

* Presenting author