Nematode (Otostrongylus circumlitus) infestation of northern elephant seals (Mirounga angustirostris) stranded along the central California coast

Between 1 January 1992 and 31 December 1995, 73 of 487 (15%) juvenile northern elephant seals (Mirounga angustirostris) that stranded along the central California coastline and were transported to a rehabilitation center had similar clinical signs. These signs included anorexia, depression, dehydration, and epistaxis, and were accompanied by a neutrophilia. Coagulation assays on five of these animals indicated all five were in a state of disseminated intravascular coagulation. Sixty-five of the 73 animals died, and post-mortem examination revealed heavy burdens of Otostrongylus circumlitus in the right ventricle and atrium of the hearts and pulmonary arteries, with occasional nematodes in the bronchi and bronchioles. Histologic examination of 33 of these seals showed multiple pulmonary thromboses associated with a suppurative arteritis and occasionally intravascular nematodes, suggesting disseminated intravascular coagulation triggered by an arteritis may be important in causing mortality of elephant seals infested with O. circumlitus. This pathology, combined with the observation that death of juvenile northern elephant seals infected with O. circumlitus usually occurs prior to the parasite reaching reproductive maturity, suggests this is a relatively recent host-parasite association.