Vegetative valvular endocarditis (VVE) has contributed to an Unusual Mortality Event (UME) in northern sea otters since 2002. Streptococcus bovis/equinus (SB/E) complex was isolated from cardiac lesions. Bartonella infection is also associated with VVE in different mammals, but little is known regarding its pathogenic significance in marine mammals. Our primary goal was to evaluate the role of bacterial agents, especially SB/E and Bartonella spp., in VVE and the UME in northern sea otters. Presence of these pathogens was also evaluated in southern sea otters as a comparison group. In our first investigation, we found that SB/E was isolated in 45% (23/51) of northern sea otter heart valves, and one-third of these cases were co-infected with Bartonella spp. Sequencing identified SB/E isolates as Streptoccocus infantarius subsp. coli. Our analysis demonstrated that SB/E was associated with VVE in northern sea otters. While Bartonella infection was detected using PCR in 45% (23/51) and 10% (3/30) of the heart valves of northern and southern sea otters, respectively, Bartonella infection was not associated with VVE. Phylogenetic analysis of the ITS region of Bartonella identified two potentially novel species. We then investigated the seroprevalence of Bartonella in northern and southern sea otters using an IFA assay. Antibodies against Bartonella were commonly detected in stranded and live-captured northern sea otters (50%; 24/48 and 34%; 15/44, respectively), whereas only 16% (24/148) of the stranded southern sea otters were seropositive. Antibodies to B. washoensis were frequently detected in both sea otter populations with titers ranging from 1:64 to 1:256. Exposure to Bartonella was commonly detected in mature live-captured (49%) and stranded (62%) northern sea otters, and adult stranded animals dying of infectious causes were 27 times more likely to be seropositive (95% CI = 2.62–269.4). IFA and PCR results from both investigations provided evidence that Bartonella was widely distributed among sea otters from southcentral Alaska. This study has helped define the role of SB/E and Bartonella in VVE-related sea otter mortalities in southcentral Alaska. Our findings shed light on infectious disease challenges in northern and southern sea otter populations; information that is being used in disease monitoring programs.
|Advisor:||Mazet, Jonna A.K.|
|Commitee:||Byrne, Barbara, Chomel, Bruno|
|School:||University of California, Davis|
|School Location:||United States -- California|
|Source:||MAI 50/06M, Masters Abstracts International|
|Subjects:||Wildlife Conservation, Pathology, Veterinary services|
|Keywords:||Alaska, Bartonella, Enhydra lutris, Sea otter, Streptococcus bovis/equinus, Vegetative valvular endocarditis|
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