Acute and Chronic Gas Bubble Lesions in Cetaceans Stranded in the United Kingdom

Abstract

Abstract. The first evidence suggestive of in vivo gas bubble formation in cetacea, including eight animals stranded in the UK, has recently been reported. This article presents the pathologic findings from these eight UK-stranded cetaceans and two additional UK-stranded cetacean cases in detail. Hepatic gas-filled cavitary lesions (0.2-6.0 cm diameter) involving approximately 5-90% of the liver volume were found in four (two juvenile, two adult) Risso's dolphins (Grampus griseus), three (two adult, one juvenile) common dolphins (Delphinus delphis), an adult Blainville's beaked whale (Mesoplodon densirostris), and an adult harbour porpoise (Phocoena phocoena). Histopathologic examination of the seven dolphin cases with gross liver cavities revealed variable degrees of pericavitary fibrosis, microscopic, intrahepatic, spherical, nonstaining cavities (typically 50-750 m in diameter) consistent with gas emboli within distended portal vessels and sinusoids and associated with hepatic tissue compression, hemorrhages, fibrin/organizing thrombi, and foci of acute hepatocellular necrosis. Two common dolphins also had multiple and bilateral gross renal cavities (2.0-9.0 mm diameter) that, microscopically, were consistent with acute (n ϭ 2) and chronic (n ϭ 1) arterial gas emboliinduced renal infarcts. Microscopic, bubblelike cavities were also found in mesenteric lymph node (n ϭ 4), adrenal (n ϭ 2), spleen (n ϭ 2), pulmonary associated lymph node (n ϭ 1), posterior cervical lymph node (n ϭ 1), and thyroid (n ϭ 1). No bacterial organisms were isolated from five of six cavitated livers and one of one cavitated kidneys. The etiology and pathogenesis of these lesions are not known, although a decompressionrelated mechanism involving embolism of intestinal gas or de novo gas bubble (emboli) development derived from tissues supersaturated with nitrogen is suspected.

Hyperbaric computed tomographic measurement of lung compression in seals and dolphins

“…These findings require that we reopen the discussion as to whether marine mammals are susceptible to DCS. The data we present here add credence to findings and hypotheses on the subject of susceptibility to and manifestation of DCS in bycaught and stranded marine mammals (Fernandez et al, 2005;Jepson et al, 2005;Moore et al, 2009). The data add further weight to the suggestion that marine mammals may experience supersaturation at levels that may result in asymptomatic or symptomatic inert gas bubbles when diving repetitively, acquired when lung collapse is incomplete (Hooker et al, 2009).…”

“…These data established the pathobiological basis for a hypothesis (Cox et al, 2006) that beaked whales are acutely (Fernandez et al, 2005), and other odontocetes are perhaps chronically (Jepson et al, 2005;Moore and Early, 2004), at risk of DCS.…”

“…Gas bubbles in stranded aquatic mammals have become a focus of attention since a brief report (Jepson et al, 2003) and later papers on atypical mass strandings of beaked whales (Fernandez et al, 2005) and single strandings of odontocetes (Jepson et al, 2005). These data established the pathobiological basis for a hypothesis (Cox et al, 2006) that beaked whales are acutely (Fernandez et al, 2005), and other odontocetes are perhaps chronically (Jepson et al, 2005;Moore and Early, 2004), at risk of DCS.…”

Last “Atypical” Beaked Whales Mass Stranding in the Canary Islands(July, 2004)

“…However, the evidence of fat emboli in these beaked whales together with the fact that all three died at sea, are highly suggestive that fat emboli was not due to trauma during stranding but was triggered and developed at sea and probably contributing to the whales relatively rapid death. This also shows that fat embolism is an important pathological finding that can still be investigated even in moderate to advanced autolytic stranded cetaceans [7,12].…”

Strandings as indicators of marine mammal biodiversity and human interactions off the coast of North Carolina

“…Marine mammal strandings (hereafter 'strandings') provide researchers with rare access to protected species and serve as an invaluable source of information on their spatiotemporal distribution (e.g., Maldini et al, 2005;Nemiroff et al, 2010), and biology (e.g., Fernandez and Hohn, 1998;Thayer et al, 2003;Gannon and Waples, 2004). In addition, stranding investigations have been critical in documenting human-induced serious injuries and mortality, such as from vessel strikes (e.g., CampbellMalone et al, 2008), fi shery entanglements (e.g., Byrd et al, 2008;Cassoff et al, 2011), and sonar effects (e.g., Jepson et al, 2005). Changes in temporal or spatial patterns of strandings may serve as indicators of underlying changes in the source populations that were driven either by human causes (see previous references in this paragraph) or by naturally occurring events (e.g., Evans et al, 2005;Johnston et al, 2012;Peltier et al, 2013).…”