Novel “gas embolic syndrome” in beaked whales resembling decompression sickness

Abstract

Lesions consistent with in vivo bubble formation in beaked whales has been recently described in Nature by Fernández et al., and Jepson et al. A Decompression Like Syndrome has been postulated to happen in whales in response to sonar exposure and might result from behavioral changes to normal dive profiles, causing excessive nitrogen supersaturation in the tissues (as occurs in decompression sickness); alternatively, bubble formation might result from a physical effect of sonar on in vivo bubble presursors (gas nuclei) in nitrogen supersaturated tissues. As Gas Embolism “in vivo” is difficult to determine some time after death, fresh cases are certainly needed for this aim. One adult female and one old male Blainville´s beaked whales (Mesoplodon densirostris) stranded on the coasts of Gran Canaria and Tenerife in 2003 and 2004 respectively. Both animals were necropsied around 4 to 8 hours after died. A routine necropsy for whales was carried out by pathologist. A routine histological study was also performed in all the sampled organs, as well as a microbiological study. Possible relationship with sonar exposure is, up to date, not known. Both animals showed massive gas bubbles in the portomesenteric system, involving changes in the liver. Gas bubbles were seen macro and microscopically in the venous system, including portomesenteric system, liver, lung, kidney, heart and brain. Although test of nitrogen content of the gas is now underway, the pathological picture is consistent with a severe acute systemic gas embolism in DCS in humans. No bacterial pathogens were found. The present results restate the occurrence of “systemic gas embolism” in beaked whales, a new pathology entity to be described in cetaceans, with special attention to deep, long time diving species. Triggering causes of this “embolic syndrome” should be further investigated.