Coxiella burnetii in northern fur seals and Steller sea lions of Alaska.

Coxiella burnetii, a zoonotic bacterium, has recently been identified in several marine mammal species on the Pacific Coast of North America, but little is known about the epidemiology, transmission, and pathogenesis in these species. We tested sera archived from northern fur seals (NFS, Callorhinus ursinus; n=236) and Steller sea lions (SSL, Eumetopias jubatus; n=72) sampled in Alaska for C. burnetii antibodies, and vaginal swabs from NFS (n=40) for C. burnetii by qPCR. The antibody prevalence in NFS samples from 2009 and 2011 (69%) was significantly higher than in 1994 (49%). The antibody prevalence of SSL samples from 2007 to 2011 was 59%. All NFS vaginal swabs were negative for C. burnetii, despite an 80% antibody prevalence in the matched sera. The significant increase in antibody prevalence in NFS from 1994 to 2011 suggests that the pathogen may be increasingly common or that there is marked temporal variation within the vulnerable NFS population. The high antibody prevalence in SSL suggests that this pathogen may also be significant in the endangered SSL population. These results confirm that C. burnetii is more prevalent within these populations than previously known. More research is needed to determine how this bacterium may affect individual, population, and reproductive health of marine mammals.

Population structure as revealed by mtDNA and microsatellites in northern fur seals, Callorhinus ursinus, throughout their range.

BACKGROUND: The northern fur seal (Callorhinus ursinus; NFS) is a widely distributed pinniped that has been shown to exhibit a high degree of philopatry to islands, breeding areas on an island, and even to specific segments of breeding areas. This level of philopatry could conceivably lead to highly genetically divergent populations. However, northern fur seals have the potential for dispersal across large distances and have experienced repeated rapid population expansions following glacial retreat and the more recent cessation of intensive harvest pressure. METHODOLOGY/PRINCIPAL FINDINGS: Using microsatellite and mitochondrial loci, we examined population structure in NFS throughout their range. We found only weak population genetic structure among breeding islands including significant F(ST) and Phi(ST) values between eastern and western Pacific islands. CONCLUSIONS: We conclude that insufficient time since rapid population expansion events (both post glacial and following the cessation of intense harvest pressure) mixed with low levels of contemporary migration have resulted in an absence of genetic structure across the entire northern fur seal range.