Leptospirosis in Northern Sea Otters (Enhydra lutris kenyoni) from Washington

We diagnosed leptospirosis in six northern sea otters (Enhydra lutris kenyoni) that stranded on beaches in Washington, US in 2002. Significant gross findings included cyanotic oral mucous membranes, renal swelling, congestion or pale streaks on the cut surface of the lobules, hematuria, dehydration, lymphadenopathy, pulmonary congestion and rarely adrenal hemorrhage and congestion. Histopathology showed lymphoplasmacytic tubulointerstitial nephritis with intraluminal spirochetes and immunoreactivity to leptospiral antigens in the renal tubules and interstitium. qPCR using kidney or urine for the leptospiral lipL32 gene was positive with cycle threshold values indicative of abundant or moderate amounts of nucleic acid. A microscopic agglutination test showed the highest serum antibody titer to serovar Pomona and titers to serovars Autumnalis, Bratislava, Hebdomadis, Grippo, Ictero, Pyrogenes, Ballum, Canicola, and Hardjo. While antibodies to Leptospira interrogans have been previously detected in sea otters, there are no reports of disease or descriptions of pathology.