[1] Michigan State Univ, Coll Vet Med, Dept Clin Sci, E Lansing, MI 48824 USA
[2] Colorado State Univ, Coll Vet Med, Dept Microbiol Immunol & Pathol, Ft Collins, CO 80524 USA
[3] Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Marine Mammal Lab, Seattle, WA 98115 USA