Bartonellaspp. Exposure in Northern and Southern Sea Otters in Alaska and California

Abstract

Since 2002, an increased number of northern sea otters (Enhydra lutris kenyoni) from southcentral Alaska have been reported to be dying due to endocarditis and/or septicemia with infection by Streptococcus infantarius subsp. coli. Bartonella spp. DNA was also detected in northern sea otters as part of mortality investigations during this unusual mortality event (UME) in Kachemak Bay, Alaska. To evaluate the extent of exposure to Bartonella spp. in sea otters, sera collected from necropsied and live-captured northern sea otters, as well as necropsied southern sea otters (Enhydra lutris nereis) unaffected by the UME, were analyzed using an immunofluorescent antibody assay. Antibodies against Bartonella spp. were detected in sera from 50% of necropsied and 34% of presumed healthy, live-captured northern sea otters and in 16% of necropsied southern sea otters. The majority of sea otters with reactive sera were seropositive for B. washoensis, with antibody titers ranging from 1:64 to 1:256. Bartonella spp. antibodies were especially common in adult northern sea otters, both free-living (49%) and necropsied (62%). Adult stranded northern sea otters that died from infectious causes, such as opportunistic bacterial infections, were 27 times more likely to be Bartonella seropositive than adult stranded northern sea otters that died from noninfectious causes ( p < 0.001; 95% confidence interval 2.62-269.4). Because Bartonella spp. antibodies were detected in necropsied northern sea otters from southcentral (44%) and southwestern (86%) stocks of Alaska, as well as in necropsied southern sea otters (16%) in southcentral California, we concluded that Bartonella spp. exposure is widely distributed among sea otter populations in the Eastern Pacific, providing context for investigating future disease outbreaks and monitoring of Bartonella infections for sea otter management and conservation.

Mustelids

“…Coinfection with multiple species of Bartonella sp. was identified in both northern and southern sea otters, but infection prevalence was not correlated with the observed lesions (Carrasco et al, 2014).…”

Sea otter population collapse in southwest Alaska: assessing ecological covariates, consequences, and causal factors

“…Mortality rates tend to be higher in populations that exist at or near carrying capacity, reflected in beach cast carcasses (Bodkin & Ballachey 1996. Conversely, even large but still growing populations may produce lower numbers of stranded carcasses, consistent with lower mortality rates (Kenyon 1969), although strandings of some segments of such growing populations (such as males) may occur following acute disease exposure events (Carrasco et al 2014). For these reasons, comparative information on the occurrence of stranded carcasses or remains through time or among islands/locations can be a useful adjunct in assessing the status of populations.…”

“…In the case of the final data type, "documented observations of deaths," we rely on previously published accounts of sea otter mortality that directly pertain to one or more hypothesized causal agents, and their distribution in time and space. Published reports on the spatiotemporal distribution (in Alaska) of exposure to and/ or mortality from disease (Goldstein et al 2009, Goldstein et al 2011, Carrasco et al 2014, Lefebvre et al 2016, fisheries interactions and human harvest (DeGange & Vacca 1989, Raymond et al 2019) and predation (Estes et al 1998, Hatfield et al 1998 were inconsistent with disease or fisheries/harvest mortality as a primary cause of decline but were consistent with predation as a primary cause of decline assuming the predator left no remains to be found.…”

Comparative Ecology of Bartonella and Brucella Infections in Wild Carnivores

“…Two B. henselae sequences detected in the spleen of raccoon dogs in Korea matched the strain Houston-1 and by ITS sequences were 99.8% similar to a strain found in dogs in China (94). Northern and Southern sea otters were found IFA positive for B. washoensis (107, 108). The authors also detected B. bacilliformis by PCR in heart valves of both species.…”

“…Analysis of the Bartonella ITS region identified two Bartonella species in those animals: a novel species closely related to Bartonella washoensis and Candidatus B. volans, whereas another genotype was molecularly identical to B. henselae . Sera from 50% of necropsied and 34% of presumed healthy, live-captured northern sea otters and in 16% of necropsied southern sea otters contained antibodies against Bartonella species (107).…”