Abstract

During an investigation of high mortality of California sea lion (Zalophus californianus) and Northern fur seal (Callorhinus ursinus) pups on San Miguel Island in southern California, hookworm (Uncinaria spp.) enteritis with secondary bacteremia was found in 65% of the 225 pups examined. Ages ranged from 2 weeks to 9 months. Lesions found in these pups included parasitic enteritis, peritonitis, myocarditis, hepatitis, encephalitis, nephritis, pneumonia, and arthritis. Adult parasites including eggs were even found within the peritoneal cavity causing peritonitis. This severe epizootic hookworm infection is having an effect on the population of these two species of marine mammals. Over the last 30 years or so the populations of California sea lions and fur seals have steadily increased causing the rookery to become fairly crowded, thus this recent problem with hookworms is considered to be a density dependent disease.

Literature Cited

1.  Lyons ET, DeLong RL, Spraker TR, Melin SR, Tolliver SC. Observations in 2001 on hookworms (Uncinaria spp.) in otariid pinnipeds. Parasitol Res. 2003;89, 503–505.

2.  Lawrence CE. Is there a common mechanism of gastrointestinal nematode expulsion? Parasite Immunol. 2003;25:271–281.

3.  Spraker TR, Lyons ET, DeLong RL, Zink RR. Penetration of the small intestine of a California sea lion (Zalophus californianus) pup by adult hookworms (Uncinaria spp). Parasitol Res. 2004;92:436–438.