Histopathologic Lesions in Sea Otters Exposed to Crude Oil

Following th e Exxon Valdez oil spill in Prince William Soun d, Alaska, sea ott ers (Enh ydra lutris) that app eared to be conta minated with oi l, that were in dan ger of becom ing conta mi nated, or th at were behavin g abnor ma lly were captured and taken to rehabilitation centers. Exposure to oil was assessed by visual examination when otte rs ar rived at the centers . Degree of oil exposure was graded accord ing to th e following criteria: oil cove ring greater than 60% of th e body-heavily conta minate d; oil covering 30-60% of th e body-moderat ely contaminated; oil cover ing less than 30% of th e bod y or light sheen on fur - lightly conta minated. If th ere was no oil visi ble, otters were conside red uncont aminat ed. Ti ssues from 51 oil-conta minated sea otte rs (14 mal es, 37 fem ales) and fro m six uncontaminated sea otte rs (thr ee males, three fem ales) th at died in rehab ilitat ion centers were exa mined histologically. Amo ng oil-conta minated sea otte rs, 19/4 6 had int erstitial pulmonary emphysema, 13/4 0 had gastric erosio n and hem or rhage, 11/4 7 had centrilobular hepat ic necrosis, 14/4 7 had periportal to di ffuse hepat ic lipid osis, and 10/4 2 had renal tubul ar lipidos is. Of th e uncontam inated sea otters , 1/ 6 had gastric ero sion and hemorrha ge and 1/ 6 had diffuse hepat ic lipidosis. Histologic exa minatio ns were perform ed on tissues from fi ve sea otte rs (thr ee males, two fem ales) found dead with external oil present 15 to 16 days after th e spill. Periportal hepati c lipidosis and renal tubul ar lipidosis were found in 3/5 , and interstiti al pulm onary emphysem a was found in 1/ 5. Tissues fro m six appare ntly normal sea otte rs (four males, two femal es) collected fro m an area not affected by an oil spill were exam ined histologically, and none of these lesion s were found . We conclude that int erstitial pulm onar y em physema, centrilobular hepati c necrosis, and hepati c and renal lipid osis of sea otte rs were assoc iated with exposure to crude oil. Gas tric eros ion and hemor rhage may have been associated with stress of captivity and/o r oil expos ure.