Novel lambdapapillomavirus in northern sea otters Enhydra lutris kenyoni, associated with oral hyperplastic nodules.

A novel papillomavirus (PV) associated with hyperplastic nodules scattered over the muco-cutaneous border of the oral cavity of a dead, wild, subadult northern sea otter Enhydra lutris kenyoni (NSO) in 2004 in Homer, Alaska, USA, was genetically characterized. Primers for the amplification of 2 large overlapping DNA fragments that contained the complete genome of the NSO PV were designed. Sanger methodology generated sequences from which new specific primers were designed for the primer-walking approach. The NSO PV genome consists of 8085 nucleotides and contains an early region composed of E6, E7, E1, and E2 open reading frames (ORFs), an E4 ORF (contained within E2) lacking an in-frame proximal ATG start codon, an unusually long (907 nucleotide) stretch lacking any ORFs, a late region that contains the capsid genes L2 and L1, and a non-coding regulatory region (ncRR). This NSO PV has been tentatively named Enhydra lutris kenyoni PV2 (ElkPV2). Pairwise and multiple sequence alignments of the complete L1 ORF nucleotides and concatenated E1-E2-L1 amino acid sequences showed that the NSO PV is a novel PV, phylogenetically most closely related to southern sea otter PV1. The carboxy end of the E6 oncoprotein does not contain the PDZ-binding motif with a strong correlation with oncogenicity, suggesting a low-risk PV, which is in agreement with histopathological findings. However, the ElkPV2 E7 oncoprotein does contain the retinoblastoma (pRb) binding domain LXCXE (LQCYE in ElkPV2), associated with oncogenicity in some high-risk PVs. Further studies on the prevalence and clinical significance of ElkPV2 infections in NSO are needed.

Primary intracranial fibrosarcoma in a southern sea otter Enhydra lutris nereis.

Southern sea otters Enhydra lutris nereis, a threatened marine mammal species, face numerous environmental and infectious disease challenges in their native habitat of coastal California, USA. However, there are few published cases describing neoplasia in sea otters despite their relatively long life span when cared for in aquarium settings. An 18 yr old neutered male southern sea otter, born and raised in human care, presented with an acute onset of seizures and dull mentation. Magnetic resonance imaging of the head revealed a large, central brain lesion. After no improvement with treatment, euthanasia was elected due to a poor prognosis. Grossly, a poorly demarcated, granular, tan mass expanded the cranial meninges in the longitudinal fissure at the level of the cruciate sulcus and extended into the underlying gray matter and superficial white matter. Histologically, the mass was composed of spindle cells, forming haphazardly arranged interlacing bundles and herringbone patterns, with a high mitotic count, moderate cellular pleomorphism, and prominent vascularization. Neoplastic cells demonstrated positive immunoreactivity for vimentin and negative immunoreactivity for smooth muscle actin, factor VIII-related antigen, S100, melan-A, E-cadherin, desmin, glial fibrillary acidic protein, and cytokeratin AE1/AE3. Based on gross, histologic, and immunohistochemical findings, the mass was most consistent with a primary intracranial fibrosarcoma (PIF). PIFs are a rare neoplasm in both humans and other animals with few reports in the veterinary literature. This is the first recorded case of a PIF in a sea otter.

Type X strains of Toxoplasma gondii are virulent for southern sea otters (Enhydra lutris nereis) and present in felids from nearby watersheds.

Why some Toxoplasma gondii-infected southern sea otters (Enhydra lutris nereis) develop fatal toxoplasmosis while others have incidental or mild chronic infections has long puzzled the scientific community. We assessed robust datasets on T. gondii molecular characterization in relation to detailed necropsy and histopathology results to evaluate whether parasite genotype influences pathological outcomes in sea otters that stranded along the central California coast. Genotypes isolated from sea otters were also compared with T. gondii strains circulating in felids from nearby coastal regions to assess land-to-sea parasite transmission. The predominant T. gondii genotypes isolated from 135 necropsied sea otters were atypical Type X and Type X variants (79%), with the remainder (21%) belonging to Type II or Type II/X recombinants. All sea otters that died due to T. gondii as a primary cause of death were infected with Type X or X-variant T. gondii strains. The same atypical T. gondii strains were detected in sea otters with fatal toxoplasmosis and terrestrial felids from watersheds bordering the sea otter range. Our results confirm a land-sea connection for virulent T. gondii genotypes and highlight how faecal contamination can deliver lethal pathogens to coastal waters, leading to detrimental impacts on marine wildlife.

Active touch in sea otters: in-air and underwater texture discrimination thresholds and behavioral strategies for paws and vibrissae.

Sea otters (Enhydra lutris) are marine predators that forage on a wide array of cryptic, benthic invertebrates. Observational studies and anatomical investigations of the sea otter somatosensory cortex suggest that touch is an important sense for detecting and capturing prey. Sea otters have two well-developed tactile structures: front paws and facial vibrissae. In this study, we use a two-alternative forced choice paradigm to investigate tactile sensitivity of a sea otter subject's paws and vibrissae, both in air and under water. We corroborate these measurements by testing human subjects with the same experimental paradigm. The sea otter showed good sensitivity with both tactile structures, but better paw sensitivity (Weber fraction, c=0.14) than vibrissal sensitivity (c=0.24). The sea otter's sensitivity was similar in air and under water for paw (cair=0.12, cwater=0.15) and for vibrissae (cair=0.24, cwater=0.25). Relative to the human subjects we tested, the sea otter achieved similar sensitivity when using her paw and responded approximately 30-fold faster regardless of difficulty level. Relative to non-human mammalian tactile specialists, the sea otter achieved similar or better sensitivity when using either her paw or vibrissae and responded 1.5- to 15-fold faster near threshold. Our findings suggest that sea otters have sensitive, rapid tactile processing capabilities. This functional test of anatomy-based hypotheses provides a mechanistic framework to interpret adaptations and behavioral strategies used by predators to detect and capture cryptic prey in aquatic habitats.

Complete genome sequence of a novel sea otterpox virus.

Members of the Poxviridae family are large, double-stranded DNA viruses that replicate in the cytoplasm of their host cells. The subfamily Chordopoxvirinae contains viruses that infect a wide range of vertebrates including marine mammals within the Balaenidae, Delphinidae, Mustelidae, Odobenidae, Otariidae, Phocidae, and Phocoenidae families. Recently, a novel poxvirus was found in a northern sea otter pup (Enhydra lutris kenyoni) that stranded in Alaska in 2009. The phylogenetic relationships of marine mammal poxviruses are not well established because of the lack of complete genome sequences. The current study sequenced the entire sea otterpox virus Enhydra lutris kenyoni (SOPV-ELK) genome using an Illumina MiSeq sequencer. The SOPV-ELK genome is the smallest poxvirus genome known at 127,879 bp, is 68.7% A+T content, is predicted to encode 132 proteins, and has 2546 bp inverted terminal repeats at each end. Genetic and phylogenetic analyses based on the concatenated amino acid sequences of 7 chorodopoxvirus core genes revealed the SOPV-ELK is 52.5-74.1% divergent from other known chordopoxviruses and is most similar to pteropoxvirus from Australia (PTPV-Aus). SOPV-ELK represents a new chordopoxvirus species and may belong to a novel genus. SOPV-ELK encodes eight unique genes. While the function of six predicted genes remains unknown, two genes appear to function as novel immune-modulators. SOPV-ELK-003 appears to encode a novel interleukin-18 binding protein (IL-18 BP), based on limited sequence and structural similarity to other poxviral IL-18 BPs. SOPV-ELK-035 appears to encode a novel tumor necrosis factor receptor-like (TNFR) protein that may be associated with the depression of the host's antiviral response. Additionally, SOPV-ELK-036 encodes a tumor necrosis factor-like apoptosis-inducing ligand (TRAIL) protein that has previously only been found in PTPV-Aus. The SOPV-ELK genome is the first mustelid poxvirus and only the second poxvirus from a marine mammal to be fully sequenced. Sequencing of the SOPV-ELK genome is an important step in unraveling the position of marine mammal poxviruses within the larger Poxviridae phylogenetic tree and provides the necessary sequence to develop molecular tools for future diagnostics and epidemiological studies.

From the predictable to the unexpected: kelp forest and benthic invertebrate community dynamics following decades of sea otter expansion.

The recovery of predators has the potential to restore ecosystems and fundamentally alter the services they provide. One iconic example of this is keystone predation by sea otters in the Northeast Pacific. Here, we combine spatial time series of sea otter abundance, canopy kelp area, and benthic invertebrate abundance from Washington State, USA, to examine the shifting consequences of sea otter reintroduction for kelp and kelp forest communities. We leverage the spatial variation in sea otter recovery to understand connections between sea otters and the kelp forest community. Sea otter increases created a pronounced decline in sea otter prey-particularly kelp-grazing sea urchins-and led to an expansion of canopy kelps from the late 1980s until roughly 2000. However, while sea otter and kelp population growth rates were positively correlated prior to 2002, this association disappeared over the last two decades. This disconnect occurred despite surveys showing that sea otter prey have continued to decline. Kelp area trends are decoupled from both sea otter and benthic invertebrate abundance at current densities. Variability in kelp abundance has declined in the most recent 15 years, as it has the synchrony in kelp abundance among sites. Together, these findings suggest that initial nearshore community responses to sea otter population expansion follow predictably from trophic cascade theory, but now, other factors may be as or more important in influencing community dynamics. Thus, the utility of sea otter predation in ecosystem restoration must be considered within the context of complex and shifting environmental conditions.

The high cost of reproduction in sea otters necessitates unique physiological adaptations.

Superimposed on inherently high basal metabolic demands, the additional energetic requirements of reproduction can push female sea otters beyond physiological limits. Indeed, the resulting energy imbalance contributes to disproportionately high rates of mortality at the end of lactation in this species. To examine and quantify metabolic changes associated with reproduction, we measured the resting metabolic rate (RMR) of a female sea otter across gestation, lactation and non-reproductive periods. Concurrently, measurements were made on a non-breeding control female. Our results suggest that RMR declines during gestation. Conversely, RMR increases during lactation, reaches a peak at 3-4 months postpartum, and remains elevated until weaning. Combining these direct measurements with published data, we found the cost of pup rearing to be significantly higher than previously estimated. High baseline energy demands and limited energy reserves, combined with significant lactation and pup rearing costs, appear to necessitate metabolic and thermal lability during key reproductive stages.

California mussels (Mytilus californianus) as sentinels for marine contamination with Sarcocystis neurona.

Sarcocystis neurona is a terrestrial parasite that can cause fatal encephalitis in the endangered Southern sea otter (Enhydra lutris nereis). To date, neither risk factors associated with marine contamination nor the route of S. neurona infection to marine mammals has been described. This study evaluated coastal S. neurona contamination using California mussels (Mytilus californianus) as sentinels for pathogen pollution. A field investigation was designed to test the hypotheses that (1) mussels can serve as sentinels for S. neurona contamination, and (2) S. neurona contamination in mussels would be highest during the rainy season and in mussels collected near freshwater. Initial validation of molecular assays through sporocyst spiking experiments revealed the ITS-1500 assay to be most sensitive for detection of S. neurona, consistently yielding parasite amplification at concentrations ⩾5 sporocysts/1 mL mussel haemolymph. Assays were then applied on 959 wild-caught mussels, with detection of S. neurona confirmed using sequence analysis in three mussels. Validated molecular assays for S. neurona detection in mussels provide a novel toolset for investigating marine contamination with this parasite, while confirmation of S. neurona in wild mussels suggests that uptake by invertebrates may serve as a route of transmission to susceptible marine animals.

Energetic demands of immature sea otters from birth to weaning: implications for maternal costs, reproductive behavior and population-level trends.

Sea otters (Enhydra lutris) have the highest mass-specific metabolic rate of any marine mammal, which is superimposed on the inherently high costs of reproduction and lactation in adult females. These combined energetic demands have been implicated in the poor body condition and increased mortality of female sea otters nearing the end of lactation along the central California coast. However, the cost of lactation is unknown and currently cannot be directly measured for this marine species in the wild. Here, we quantified the energetic demands of immature sea otters across five developmental stages as a means of assessing the underlying energetic challenges associated with pup rearing that may contribute to poor maternal condition. Activity-specific metabolic rates, daily activity budgets and field metabolic rates (FMR) were determined for each developmental stage. Mean FMR of pre-molt pups was 2.29 ± 0.81 MJ day(-1) and increased to 6.16 ± 2.46 and 7.41 ± 3.17 MJ day(-1) in post-molt pups and dependent immature animals, respectively. Consequently, daily energy demands of adult females increase 17% by 3 weeks postpartum and continue increasing to 96% above pre-pregnancy levels by the average age of weaning. Our results suggest that the energetics of pup rearing superimposed on small body size, marine living and limited on-board energetic reserves conspire to make female sea otters exceptionally vulnerable to energetic shortfalls. By controlling individual fitness, maternal behavior and pup provisioning strategies, this underlying metabolic challenge appears to be a major factor influencing current population trends in southern sea otters (Enhydra lutris nereis).

Data needs for sea otter bioenergetics modeling.

Sea otters are keystone predators whose recovery and expansion from historical exploitation throughout their range can serve to enhance local biodiversity, promote community stability, and buffer against habitat loss in nearshore marine systems. Bioenergetics models have become a useful tool in conservation and management efforts of marine mammals generally, yet no bioenergetics model exists for sea otters. Previous research provides abundant data that can be used to develop bioenergetics models for this species, yet important data gaps remain. Here we review the available data that could inform a bioenergetics model, and point to specific open questions that could be answered to more fully inform such an effort. These data gaps include quantifying energy intake through foraging by females with different aged pups in different quality habitats, the influence of body size on energy intake through foraging, and determining the level of fat storage that is possible in sea otters of different body sizes. The more completely we fill these data gaps, the more confidence we can have in the results and predictions produced by future bioenergetics modeling efforts for this species.

Species distribution modeling of northern sea otters (Enhydra lutris kenyoni) in a data-limited ecosystem.

Species distribution models (SDMs) are used to map and predict the geographic distributions of animals based on environmental covariates. Typically, SDMs require high-resolution habitat data and time series information on animal locations. For data-limited regions, defined as having scarce habitat or animal survey data, modeling is more challenging, often failing to incorporate important environmental attributes. For example, for sea otters (Enhydra lutris), a federally protected keystone species with variable population trends across the species' range, predictive modeling of distributions has been successfully conducted in areas with robust sea otter population and habitat data. We used open-access data and employed a presence-only model, maximum entropy (MaxEnt), to investigate subtidal habitat associations (substrate and algal cover, bathymetry, and rugosity) of northern sea otters (E. lutris kenyoni) for a data-limited ecosystem, represented by Kachemak Bay, Alaska. Habitat association results corroborated previous findings regarding the importance of bathymetry and understory kelp as predictors of sea otter presence. Novel associations were detected as filamentous algae and shell litter were positively and negatively associated with northern sea otter presence, respectively, advancing existing knowledge of sea otter benthic habitat associations useful for predicting habitat suitability. This study provides a quantitative framework for conducting species distribution modeling with limited temporal and spatial animal distribution and abundance data. Utilizing drop camera information, our novel approach allowed for a better understanding of habitat requirements for a stable northern sea otter population, including bathymetry, understory kelp, and filamentous algae as positive predictors of sea otter presence in Kachemak Bay, Alaska.

Mercury content in the fur of sea otters (Enhydra lutris) from the Commander Islands.

The sea otter (Enhydra lutris) is a keystone species in the ecosystem which is currently in depression in Russia. The objectives of this study were to: (1) establish if the sea otters from the Commander Islands have hazardous levels of mercury (Hg) in their fur; (2) assess Hg pollution in sea otters during a period of high abundance and population depression; (3) identify the age and sex differences in sea otters by Hg content. The sea otters were classified from no to low risk for Hg health effects. Differences in Hg content during periods of low and high population size were not statistically significant. Hg concentrations in adult sea otters were significantly higher than in the young, and higher in males than in females. This study presents the first data on Hg content in sea otters' fur and the first estimate of Hg contamination for the Commander Islands population.

Macronutrient composition of sea otter diet with respect to recolonization, life history, and season in southern Southeast Alaska.

The sea otter (Enhydra lutris) population of Southeast Alaska has been growing at a higher rate than other regions along the Pacific coast. While good for the recovery of this endangered species, rapid population growth of this apex predator can create a human-wildlife conflict, negatively impacting commercial and subsistence fishing. Previous foraging studies throughout the sea otter range have shown they will reduce invertebrate prey biomass when recolonizing an area. The goal of this study was to examine and quantify the energy content of sea otter diets through direct foraging observations and prey collection. Our study area, Prince of Wales Island in southern Southeast Alaska, exhibits a gradient of sea otter recolonization, thus providing a natural experiment to test diet change in regions with different recolonization histories. Sea otter prey items were collected in three seasons (spring, summer, and winter) to measure caloric value and lipid and protein content. We observed 3523 sea otter dives during the spring and summer. A majority of the sea otter diet consisted of clams. Sea otters in newly recolonized areas had lower diet diversity, higher energetic intake rates (EIR, kcal/min), and prey had higher energy content (kcal/g). Females with pups had the highest diet diversity and the lowest EIR. Sea otter EIR were higher in the fall and winter vs. spring and summer. Sea cucumber energy and lipid content appeared to correspond with times when sea otters consumed the highest proportion of sea cucumbers. These caloric variations are an important component of understanding ecosystem-level effects sea otters have in the nearshore environment.

Molecular and morphological confirmation of Profilicollis altmani as the cause of acanthocephalan peritonitis in California sea otters (Enhydra lutris nereis).

Acanthocephalan peritonitis (AP; trans-intestinal migration of acanthocephalan parasites into the peritoneal cavity resulting in severe peritonitis), is a common cause of mortality in southern sea otters (Enhydra lutris nereis). Although Profilicollis spp. acanthocephalans have been implicated in these infections, the species causing AP has been an important unresolved question for decades. We used morphological and molecular techniques to characterize acanthocephalans from the gastrointestinal (GI) tract and peritoneal omentum of eighty necropsied southern sea otters. Only P. altmani was found to have perforated through the intestinal wall and migrated into the peritoneal cavity of examined sea otters, resulting in AP. Morphological and molecular criteria confirmed that Profilicollis kenti was synonymous with P. altmani. A second Profilicollis sp., likely P. botulus, was present only in the intestinal lumen, did not penetrate through the intestinal wall, and was not associated with AP.

Pathology, microbiology, and genetic diversity associated with Erysipelothrix rhusiopathiae and novel Erysipelothrix spp. infections in southern sea otters (Enhydra lutris nereis).

Erysipelothrix spp., including E. rhusiopathiae, are zoonotic bacterial pathogens that can cause morbidity and mortality in mammals, fish, reptiles, birds, and humans. The southern sea otter (SSO; Enhydra lutris nereis) is a federally-listed threatened species for which infectious disease is a major cause of mortality. We estimated the frequency of detection of these opportunistic pathogens in dead SSOs, described pathology associated with Erysipelothrix infections in SSOs, characterized the genetic diversity and antimicrobial susceptibility of SSO isolates, and evaluated the virulence of two novel Erysipelothrix isolates from SSOs using an in vivo fish model. From 1998 to 2021 Erysipelothrix spp. were isolated from six of >500 necropsied SSOs. Erysipelothrix spp. were isolated in pure culture from three cases, while the other three were mixed cultures. Bacterial septicemia was a primary or contributing cause of death in five of the six cases. Other pathology observed included suppurative lymphadenopathy, fibrinosuppurative arteritis with thrombosis and infarction, bilateral uveitis and endophthalmitis, hypopyon, petechia and ecchymoses, mucosal infarction, and suppurative meningoencephalitis and ventriculitis. Short to long slender Gram-positive or Gram-variable bacterial rods were identified within lesions, alone or with other opportunistic bacteria. All six SSO isolates had the spaA genotype-four isolates clustered with spaA E. rhusiopathiae strains from various terrestrial and marine animal hosts. Two isolates did not cluster with any known Erysipelothrix spp.; whole genome sequencing revealed a novel Erysipelothrix species and a novel E. rhusiopathiae subspecies. We propose the names Erysipelothrix enhydrae sp. nov. and Erysipelothrix rhusiopathiae ohloneorum ssp. nov. respectively. The type strains are E. enhydrae UCD-4322-04 and E. rhusiopathiae ohloneorum UCD-4724-06, respectively. Experimental injection of tiger barbs (Puntigrus tetrazona) resulted in infection and mortality from the two novel Erysipelothrix spp. Antimicrobial susceptibility testing of Erysipelothrix isolates from SSOs shows similar susceptibility profiles to isolates from other terrestrial and aquatic animals. This is the first description of the pathology, microbial characteristics, and genetic diversity of Erysipelothrix isolates recovered from diseased SSOs. Methods presented here can facilitate case recognition, aid characterization of Erysipelothrix isolates, and illustrate assessment of virulence using fish models.

Anatomy of the sense of touch in sea otters: Cutaneous mechanoreceptors and structural features of glabrous skin.

Sea otters (Enhydra lutris) demonstrate rapid, accurate tactile abilities using their paws and facial vibrissae. Anatomical investigations of neural organization in the vibrissal bed and somatosensory cortex coincide with measured sensitivity, but no studies describe sensory receptors in the paws or other regions of glabrous (i.e., hairless) skin. In this study, we use histology to assess the presence, density, and distribution of mechanoreceptors in the glabrous skin of sea otters: paws, rhinarium, lips, and flipper digits, and we use scanning electron microscopy to describe skin-surface texture and its potential effect on the transduction of mechanical stimuli. Our results confirm the presence of Merkel cells and Pacinian corpuscles, but not Meissner corpuscles, in all sea otter glabrous skin. The paws showed the highest density of Merkel cells and Pacinian corpuscles. Within the paw, relative densities of mechanoreceptor types were highest in the distal metacarpal pad and digits, which suggests that the distal paw is a tactile fovea for sea otters. In addition to the highest receptor density, the paw displayed the thickest epidermis. Rete ridges (epidermal projections into the dermis) and dermal papillae (dermal projections into the epidermis) were developed across all glabrous skin. These quantitative and qualitative descriptions of neural organization and physical features, combined with previous behavioral results, contribute to our understanding of how structure relates to function in the tactile modality. Our findings coincide with behavioral observations of sea otters, which use touch to maintain thermoregulatory integrity of their fur, explore objects, and capture visually cryptic prey.

INVESTIGATING ASSOCIATIONS AMONG RELATEDNESS, GENETIC DIVERSITY, AND CAUSES OF MORTALITY IN SOUTHERN SEA OTTERS (ENHYDRA LUTRIS NEREIS).

Southern sea otter (Enhydra lutris nereis) population recovery is influenced by a variety of factors, including predation, biotoxin exposure, infectious disease, oil spills, habitat degradation, and resource limitation. This population has also experienced a significant genetic bottleneck, resulting in low genetic diversity. We investigated how two metrics, familial relatedness and genetic diversity, are correlated with common causes of mortality in southern sea otters, including cardiomyopathy, acanthocephalan (Profilicollis spp.) peritonitis, systemic protozoal infection (Toxoplasma gondii and Sarcocystis neurona), domoic acid intoxication, end-lactation syndrome, and shark bite. Microsatellite genetic markers were used to examine this association in 356 southern sea otters necropsied from 1998 to 2012. Significant associations with genetic diversity or familial relatedness (P<0.05) were observed for cardiomyopathy, acanthocephalan peritonitis, and sarcocystosis, and these associations varied by sex. Adult male cardiomyopathy cases (n=86) were more related than the null expectation (P<0.049). Conversely, female acanthocephalan peritonitis controls (n=110) were more related than the null expectation (P<0.004). Including genetic diversity as a predictor for fatal acanthocephalan peritonitis in the multivariate logistic model significantly improved model fit; lower genetic diversity was associated with reduced odds of sea otter death due to acanthocephalan peritonitis. Finally, male sarcocystosis controls (n=158) were more related than the null expectation (P<0.011). Including genetic diversity in the multivariate logistic model for fatal S. neurona infection improved model fit; lower genetic diversity was associated with increased odds of sea otter death due to S. neurona. Our study suggests that genetic diversity and familial relatedness, in conjunction with other factors such as age and sex, may influence outcome (survival or death) in relation to several common southern sea otter diseases. Our findings can inform policy for conservation management, such as potential reintroduction efforts, as part of species recovery.

Metals in the stomach contents and brain, gonad, kidney, and liver tissues of subsistence-harvested northern sea otters (Enhydra lutris kenyoni) from Icy Strait, Alaska.

Southeast Alaska sea otters (Enhydra lutris) have had a rapid rise in their population. As they feed primarily on sessile prey, they are excellent sentinels for examining metals contamination. Objectives of this study on sea otters were to determine: (1) concentrations of metals in different tissues; (2) whether metals biomagnify from stomach contents (i.e., the prey) to other tissues; (3) whether selenium and mercury concentrations indicate an overall health benefit or risk; and (4) if metals concentrations in tissues vary with body size. Brain, kidney, gonad, liver, and stomach contents were collected from freshly harvested sea otters in Icy Strait, Alaska, and analyzed for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), total mercury (THg), and selenium (Se). Metals concentrations varied significantly, and some were biomagnified, with livers and kidneys harboring the highest concentrations. Lead and arsenic appeared to be readily excreted. This study represents baseline metals concentrations to assist in monitoring the health of sea otters.

CANINE DISTEMPER VIRUS IN THE SEA OTTER (ENHYDRA LUTRIS) POPULATION IN WASHINGTON STATE, USA.

Before 2001, all serosurveys for morbilliviruses in sea otters (Enhydra lutris) in California, Washington, and Alaska, US, documented a 0% seroprevalence. The first published serologic detections of morbillivirus in sea otters occurred in 2001-02 in live-captured Washington sea otters, with a documented 80% seroprevalence. We conducted a retrospective study of sea otter cases from 1989 to 2010 compiled at the US Geological Survey, National Wildlife Health Center to identify cases of morbilliviral disease in Washington sea otters and to characterize the disease using immunohistochemistry, reverse transcription (RT)-PCR, genetic sequencing, virus isolation, and serology. We identified six cases of morbilliviral disease and 12 cases of morbilliviral infection in this population of sea otters during 2000-10. Significant histologic findings included inflammation in the white and gray matter of the brain characterized by lymphoplasmacytic perivascular cuffing, neuronal necrosis, and satellitosis in gray matter and by spongiosis, myelin degeneration, spheroids, and gemistocytes in white matter. Intranuclear and intracytoplasmic viral inclusion bodies were found in neurons, Purkinje cells, and glia. Immunohistochemistry for canine distemper virus (CDV) showed positive staining in neurons, glial cells, and cell processes. A pan-morbillivirus RT-PCR with subsequent restriction endonuclease digestion or sequencing identified CDV. Virus isolation was not successful. Two sea otters with morbilliviral encephalitis showed greater antibody titers to CDV than phocine distemper virus. Histologic changes were confined to the central nervous system and resembled neurologic canine distemper in domestic dogs. Cases of sea otters with morbilliviral infection without histologic changes could represent early infections or incompletely cleared sublethal infections. We found that morbillivirus was present in the Washington sea otter population as early as 2000, and we provide a description of the pathology of canine distemper in sea otters.

Leptospirosis in Northern Sea Otters (Enhydra lutris kenyoni) from Washington, USA.

We diagnosed leptospirosis in six northern sea otters (Enhydra lutris kenyoni) that stranded on beaches in Washington State, US in 2002. Significant gross findings included cyanotic oral mucous membranes, renal swelling, congestion or pale streaks on the cut surface of renal lobules, hematuria, dehydration, lymphadenopathy, pulmonary congestion, and rarely adrenal hemorrhage and congestion. Histopathology showed lymphoplasmacytic tubulointerstitial nephritis with intraluminal spirochetes and immunoreactivity to leptospiral antigens in the renal tubules and interstitium. A quantitative polymerase chain reaction (qPCR) using kidney or urine for the leptospiral lipL32 gene was positive with cycle threshold values indicative of abundant or moderate amounts of nucleic acid. A microscopic agglutination test showed the highest serum antibody titer to serovar Pomona and positive titers to serovars Autumnalis, Bratislava, Hebdomadis, Grippotyphosa, Icterohaemorrhagiae, Pyrogenes, Ballum, Canicola, and Hardjo. Although antibodies to Leptospira interrogans have been previously detected in sea otters, this report describes the pathology of leptospirosis in diseased free-ranging sea otters.