Morbidity and mortality in stranded Cook Inlet beluga whales Delphinapterus leucas

CAUSES AND TRENDS OF HARBOR SEAL (PHOCA VITULINA) MORTALITY ALONG THE BRITISH COLUMBIA COAST, CANADA, 2012-2020

A retrospective study was conducted to categorize and describe the causes of mortality in harbor seals (Phoca vitulina) along the British Columbia coast that presented to the Vancouver Aquarium Marine Mammal Rescue Centre (MMR) for rehabilitation from 2012 to 2020. Medical records for 1,279 predominantly perinatal live-stranded harbor seals recovered in this region were reviewed. Approximately 20.0% (256 individuals; 137 males, 118 females, 1 unknown) of these animals died while at MMR. Infectious disease was the most common cause of death, accounting for 60.5% of mortality across all age classes. This was followed by nonanthropogenic trauma (7.1%), metabolic illness (5.4%), nutritional deficiency (5.0%), parasitic illness (5.0%), congenital disorders (2.5%), and human-associated trauma (0.4%). Pups were the most common age class (87.4%) amongst mortalities and predominantly died of an infectious process (62.5%). Phocid herpesvirus-1 infection was identified in 18.9% of the mortalities, with the highest prevalence occurring in 2019 (30.8%). Fungal disease was detected in six seals: three cases of pulmonary mycosis due to Cryptococcus gattii and three cases consistent with mucormycosis. In six cases, mortality was attributed to congenital disorders. Two of these cases involved axial skeletal malformities that are not currently described in the literature. This is the first study to describe the causes of mortality in harbor seals undergoing rehabilitation in British Columbia.

Cook Inlet beluga whale Delphinapterus leucas with valvular endocarditis, encephalitis, rhabdomyolysis, heavy parasitism and fungal dermatitis

This is a case report of a Cook Inlet beluga whale Delphinapterus leucas found dead stranded on September 28, 2020 in Turnagain Arm, Alaska. This subadult male had valvular endocarditis, encephalitis, rhabdomyolysis, myoglobinuric nephropathy, severe parasitism and fungal dermatitis. Erysipelothrix rhusiopathiae was detected in the heart lesion, eye and external swabs. The level of infection and parasitism in this individual is markedly higher than what has been found in other Cook Inlet belugas, suggesting immunosuppression.

Molecular characterization of the parasitic nematode genus Crassicauda; larvae parasitic on the firefly squid and adults on beaked whales off the coast of Japan

The Spirurina type X larvae, which infect firefly squid (Watasenia scintillans), are known to cause cutaneous creeping eruption and intestinal obstruction in humans. Although it has been reported that the adult of this larva is Crassicauda giliakiana, which was recovered from a Baird's beaked whale (Berardius bairdii), it is not well known internationally. In this study, to reconfirm the identification of this species, we determined the mitochondrial cox1 gene and the partial sequence of 18S-28S ribosomal DNA from larvae recovered from firefly squid. As the results, we confirmed that the larvae were C. giliakiana, and partial ribosomal DNA sequences were also performed for phylogenetic analysis. Furthermore, to determine the distribution of the genus Crassicauda in Japan as a definitive host, DNA was extracted from archival specimens of adult worms recovered from the kidneys of family Ziphiidae that had stranded on the coast in Japan, and phylogenetic analysis using ITS2 region was conducted. As a result, C. giliakiana were detected from not only B. bairdii but also Mesoplodon stejnegeri, and Ziphius cavirostris, and C. anthonyi was also detected in Z. cavirostris. Furthermore, the kidney parasitic nematoda Crassicauda sp., which is not registered in the database, was found in both M. densirostris and M. gingkodens. This study provides new insights into the distribution and the lifecycle of genus Crassicauda in Japan based on the phylogenetic relationship between larvae and adults.

Congenital defects and herpesvirus infection in beluga whale Delphinapterus leucas calves from the Critically Endangered Cook Inlet population

Cook Inlet beluga whales (CIBs) Delphinapterus leucas are Critically Endangered and genetically distinct from other beluga populations in Alaska. CIBs are exposed to numerous natural and anthropogenic sources of mortality and morbidity. This study describes congenital defects observed in 2 CIB calves. The first case, an aborted fetus, was characterized by lack of a peduncle and flukes, anorectal and genitourinary dysgenesis, and probable biliary dysplasia. The second case, a male calf, had a perineal groove defect and suspected secondary peritonitis; it also had a systemic herpesvirus infection. Further studies are needed to determine if such defects are due to genetic mutation, infectious diseases, nutritional imbalances, or contaminant exposure.

Evaluating beluga (Delphinapterus leucas) blow samples as a potential diagnostic for immune function gene expression within the respiratory system

Evaluating respiratory health is important in the management of cetaceans, which are vulnerable to respiratory diseases. Quantifying the expression of genes related to immune function within the respiratory tract could be a valuable tool for directly assessing respiratory health. Blow (exhale) samples allow DNA analysis, and we hypothesized that RNA could also be isolated from blow samples for gene expression studies of immune function. We evaluated the potential to extract RNA from beluga blow samples and tested whether transcripts associated with immune function could be detected with endpoint polymerase chain reaction. A total of 54 blow samples were collected from clinically healthy aquarium belugas (n = 3), and 15 were collected from wild belugas temporarily restrained for health assessment in Bristol Bay, Alaska (n = 9). Although RNA yield varied widely (range, 0-265.2 ng; mean = 85.8; SD = 71.3), measurable RNA was extracted from 97% of the samples. Extracted RNA was assessed in 1-6 PCR reactions targeting housekeeping genes (Rpl8, Gapdh or ActB) or genes associated with immune function (TNFα, IL-12p40 or Cox-2). Fifty of the aquarium samples (93%) amplified at least one transcript; overall PCR success for housekeeping genes (96/110, 87%) and genes associated with immune function (90/104, 87%) were similarly high. Both RNA yield and overall PCR success (27%) were lower for wild beluga samples, which is most likely due to the reduced forcefulness of the exhale when compared with trained or free-swimming belugas. Overall, the high detection rate with PCR suggests measuring gene expression in blow samples could provide diagnostic information about immune responses within the respiratory tract. While further study is required to determine if quantitative gene expression data from blow samples is associated with disease states, the non-invasive nature of this approach may prove valuable for belugas, which face increasing anthropogenic disturbances.

Highly divergent herpesviruses in threatened river dolphins from Brazil

River dolphins are a highly threatened polyphyletic group comprised of four odontocete families: Iniidae, Pontoporiidae, Lipotidae, and Platanistidae, the first two endemic to South America. To address the knowledge gap regarding infectious agents in this cetacean group, we surveyed the presence of herpesviruses by PCR in skin and/or blood samples of live-captured Amazon (Inia geoffrensis, n = 25) and Bolivian (Inia boliviensis, n = 22) river dolphins of the Amazon basin and in selected tissue samples of franciscanas (Pontoporia blainvillei, n = 27) stranded or bycaught in southeastern Brazil. Additionally, available franciscana tissue samples were examined by histopathology. Herpesvirus DNA was amplified in 13 Bolivian river dolphins (59.1%, 95% CI 38.5–79.6%) and 14 franciscanas (51.9%, 95% CI 33.0–70.7%). All Amazon river dolphins were herpesvirus-negative. Two different herpesviruses were found in Bolivian river dolphins: a previously known gammaherpesvirus detected in blood and/or skin samples of all positive individuals and a novel alphaherpesvirus in the skin of one animal. A new gammaherpesvirus was found in several franciscana samples—the first herpesvirus recorded in Pontoporiidae. Intranuclear inclusion bodies consistent with herpesvirus were observed in the lymph node of one franciscana. The high divergence among the obtained herpesviruses and those previously described can be explained by viral-host coevolution, and by the fact that these populations are fairly isolated.

Systematic Determination of Herpesvirus in Free-Ranging Cetaceans Stranded in the Western Mediterranean: Tissue Tropism and Associated Lesions

The monitoring of herpesvirus infection provides useful information when assessing marine mammals’ health. This paper shows the prevalence of herpesvirus infection (80.85%) in 47 cetaceans stranded on the coast of the Valencian Community, Spain. Of the 966 tissues evaluated, 121 tested positive when employing nested-PCR (12.53%). The largest proportion of herpesvirus-positive tissue samples was in the reproductive system, nervous system, and tegument. Herpesvirus was more prevalent in females, juveniles, and calves. More than half the DNA PCR positive tissues contained herpesvirus RNA, indicating the presence of actively replicating virus. This RNA was most frequently found in neonates. Fourteen unique sequences were identified. Most amplified sequences belonged to the Gammaherpesvirinae subfamily, but a greater variation was found in Alphaherpesvirinae sequences. This is the first report of systematic herpesvirus DNA and RNA determination in free-ranging cetaceans. Nine (19.14%) were infected with cetacean morbillivirus and all of them (100%) were coinfected with herpesvirus. Lesions similar to those caused by herpesvirus in other species were observed, mainly in the skin, upper digestive tract, genitalia, and central nervous system. Other lesions were also attributable to concomitant etiologies or were nonspecific. It is necessary to investigate the possible role of herpesvirus infection in those cases.

Determinants of lungworm specificity in five cetacean species in the western Mediterranean

BACKGROUND

Current data about Pseudaliidae show contrasting patterns of host specificity between congeneric species. We investigated how both contact and compatibility between hosts and parasites contributed to the patterns of lungworm infection observed in a community of five species of cetaceans in the western Mediterranean.

METHODS

The lungs of 119 striped dolphins Stenella coeruleoalba, 18 bottlenose dolphins Tursiops truncatus, 7 Risso's dolphins Grampus griseus, 7 long-finned pilot whales Globicephala melas, and 6 common dolphins Delphinus delphis were analysed for lungworms. Parasites were identified by morphology and analysis of ITS2 sequences using both maximum likelihood and Bayesian inference methods. Body length was used as a proxy for lungworm species fitness in different hosts and compared with Kruskal-Wallis tests. Infection parameters were compared between cetacean species using Fisher's exact tests and Kruskal-Wallis tests. Phylogenetic specificity was explored by collating the overall lungworm species prevalence values in hosts from previous surveys in various localities. To explore the relative importance of vertical and horizontal transmission, Spearman's rank correlation was used to look for an association between host size and lungworm burden. A Mantel test was used to explore the association between lungworm species similarity and prey overlap using dietary data.

RESULTS

Halocercus delphini had higher infection levels in striped dolphins and common dolphins; Stenurus ovatus had higher infection levels in bottlenose dolphins; and Stenurus globicephalae had higher infection levels in long-finned pilot whales. These results are congruent with findings on a global scale. Morphometric comparison showed that the larger nematodes were found in the same host species that had the highest parasite burden. Lungworms were found in neonatal striped dolphins and a Risso's dolphin, and there was a weak but significant correlation between host size and parasite burden in striped dolphins and bottlenose dolphins. There was also a weak but significant association between prey overlap and lungworm species similarity.

CONCLUSIONS

Data indicate that phylogenetic specificity has an important role in governing host-parasite associations, as indicated by the higher infection levels and larger nematode size in certain hosts. However, diet can also influence infection patterns in these preferred hosts and contribute to less severe infections in other hosts.

Streptococcal Infections in Marine Mammals

Marine mammals are sentinels for the marine ecosystem and threatened by numerous factors including infectious diseases. One of the most frequently isolated bacteria are beta-hemolytic streptococci. However, knowledge on ecology and epidemiology of streptococcal species in marine mammals is very limited. This review summarizes published reports on streptococcal species, which have been detected in marine mammals. Furthermore, we discuss streptococcal transmission between and adaptation to their marine mammalian hosts. We conclude that streptococci colonize and/or infect marine mammals very frequently, but in many cases, streptococci isolated from marine mammals have not been further identified. How these bacteria disseminate and adapt to their specific niches can only be speculated due to the lack of respective research. Considering the relevance of pathogenic streptococci for marine mammals as part of the marine ecosystem, it seems that they have been neglected and should receive scientific interest in the future.

Assessing cetacean populations using integrated population models: an example with Cook Inlet beluga whales

Effective conservation and management of animal populations requires knowledge of abundance and trends. For many species, these quantities are estimated using systematic visual surveys. Additional individual-level data are available for some species. Integrated population modeling (IPM) offers a mechanism for leveraging these data sets into a single estimation framework. IPMs that incorporate both population- and individual-level data have previously been developed for birds, but have rarely been applied to cetaceans. Here, we explore how IPMs can be used to improve the assessment of cetacean populations. We combined three types of data that are typically available for cetaceans of conservation concern: population-level visual survey data, individual-level capture-recapture data, and data on anthropogenic mortality. We used this IPM to estimate the population dynamics of the Cook Inlet population of beluga whales (CIBW; Delphinapterus leucas) as a case study. Our state-space IPM included a population process model and three observational submodels: (1) a group detection model to describe group size estimates from aerial survey data; (2) a capture-recapture model to describe individual photographic capture-recapture data; and (3) a Poisson regression model to describe historical hunting data. The IPM produces biologically plausible estimates of population trajectories consistent with all three data sets. The estimated population growth rate since 2000 is less than expected for a recovering population. The estimated juvenile/adult survival rate is also low compared to other cetacean populations, indicating that low survival may be impeding recovery. This work demonstrates the value of integrating various data sources to assess cetacean populations and serves as an example of how multiple, imperfect data sets can be combined to improve our understanding of a population of interest. The model framework is applicable to other cetacean populations and to other taxa for which similar data types are available.

Novel Pulmonary Vasculitis with Splendore-Hoeppli Reaction in Grey Seals (Halichoerus grypus) Associated with Otostrongylus circumlitus Infection

Lungworm infection in seals is an important cause of morbidity and mortality, inducing bronchopneumonia and affecting population dynamics in some areas of the world. We present a series of cases of lungworm infection in grey seals (Halichoerus grypus) associated with novel, significant and unusual pulmonary vascular changes. Grey seals (n = 180) that were stranded, in rehabilitation or in long-term captivity in the UK were subjected to post-mortem examination between 2012 and 2018. Lung tissue was collected from 47 individuals for histopathological examination. Polymerase chain reaction (PCR) on formalin-fixed and paraffin wax-embedded (FFPE) material was attempted for parasite identification on selected sections using lungworm-specific primers, and nematode morphology within sections was evaluated histologically. Fourteen of 47 (30%) of these grey seals showed evidence of segmental granulomatous and eosinophilic vasculitis with an intramural Splendore-Hoeppli reaction in medium to large pulmonary arteries. Intravascular nematodes suggestive of Otostrongylus circumlitus were seen in two cases. PCR on FFPE material was unable to detect a signal on selected tissue sections. Of the 14 affected seals, nine had concurrent bronchopneumonia and four had intra-alveolar/bronchiolar Parafilaroides spp. Thirteen of 14 animals with vasculitis lesions were weaned pups with only one adult affected. Previous pathological descriptions of lungworm infection in grey seals have dealt mainly with the bronchopneumonia. This case series has identified previously unrecorded vascular changes characterized by an intramural Splendore-Hoeppli reaction. Such change would impact on vascular integrity, increasing the likelihood of vascular rupture with pulmonary haemorrhage and increased risk of intravascular coagulation. A host-parasite relationship with the persistence of antigenic material following close contact with, or migration through, the blood vessel wall is suspected.

Comparing progesterone in blubber and serum to assess pregnancy in wild beluga whales (Delphinapterus leucas)

The Cook Inlet population of beluga whales (Delphinapterus leucas) is listed as endangered and continues to decline for largely unknown reasons; however, there is some evidence that poor reproductive success is a contributing factor. Pregnancy is difficult to detect through observation, and, there is reluctance to capture endangered beluga whales for reproductive tract imaging via ultrasound or to obtain suitable samples for pregnancy assessments. An endocrine analysis of blubber biopsies collected by remote darting could represent a minimally invasive way to identify pregnant females and compare pregnancy rates among years or populations. Studies have validated the use of blubber biopsies to identify pregnant females in other cetacean species, but not beluga whales; therefore, validation of blubber progesterone levels to proven tests that reliably detect pregnancy was needed for this species. As part of a larger study, we sampled blood and blubber from live-captured beluga whales (21 females, 26 males) in Bristol Bay, Alaska. Progesterone levels were determined in serum samples obtained from all animals and in blubber samples from a subset (14 females, 13 males) to determine pregnancy status, estimate the stage of pregnancy, and evaluate the suitability of using blubber alone for these assessments. In general, there was distinct separation of high levels of progesterone in serum and blubber for presumed pregnant females and low levels for males and presumed non-pregnant females. Blubber progesterone levels in two females (14% of females tested) were intermediate (i.e. ambiguous); their corresponding serum levels were consistent with being pregnant in one case and not being pregnant in the other. Except for these two intermediate values, pregnancy status of beluga whales could be determined from blubber alone, thereby providing a valuable tool to better understand reproduction dynamics from populations that cannot be captured for examination.

Novel herpesviruses in riverine and marine cetaceans from South America

Herpesvirus (HV) infections in cetaceans are frequently associated with skin and mucosal lesions. Although HV infections have been reported worldwide, their occurrence in southern Atlantic marine mammals is still poorly understood. We tested skin, oral and genital mucosal beta-actin PCR-positive samples from 109 free-ranging Brazilian cetaceans using a universal herpesvirus DNA polymerase PCR. Herpesvirus-positive skin samples from a Guiana dolphin (Sotalia guianensis), a dwarf sperm whale (Kogia sima), a Bolivian river dolphin (Inia boliviensis), and a lingual sample from an Atlantic spotted dolphin (Stenella frontalis) were histologically evaluated. Additional tissue samples from these animals were also PCR-positive for HV, including a novel sequence obtained from the dwarf sperm whale's stomach and mesenteric lymph node. Four novel HV species were detected in the Guiana dolphin (one), the dwarf sperm whale (two) and the Bolivian river dolphin (one). The cutaneous lesions (marked, focally extensive, chronic proliferative dermatitis) of the Guiana dolphin and the Bolivian river dolphin were similar to previous HV reports in cetaceans, despite the absence of intranuclear inclusion bodies. This is the largest HV survey in South American cetaceans and the first detection of HV infection in riverine dolphins worldwide.

Leger JA, van Bonn WG, Colegrove K, Burek-Huntington KA, Suydam R, Stimmelmayr R, Wise JP, Wise SS, Beauchamp G, Martineau D. Intestinal polycyclic aromatic hydrocarbon-DNA adducts in a population of beluga whales with high levels of gastrointestinal cancers

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) were disposed directly into the Saguenay River of the St. Lawrence Estuary (SLE) by local aluminum smelters (Quebec, Canada) for 50 years (1926-1976). PAHs in the river sediments are likely etiologically related to gastrointestinal epithelial cancers observed in 7% of 156 mature (>19-year old) adult beluga found dead along the shorelines. Because DNA adduct formation provides a critical link between exposure and cancer induction, and because PAH-DNA adducts are chemically stable, we hypothesized that SLE beluga intestine would contain PAH-DNA adducts. Using an antiserum specific for DNA modified with several carcinogenic PAHs, we stained sections of paraffin-embedded intestine from 51 SLE beluga (0-63 years), 4 Cook Inlet (CI) Alaska beluga (0-26 years), and 20 beluga (0-46 years) living in Arctic areas (Eastern Beaufort Sea, Eastern Chukchi Sea, Point Lay Alaska) and aquaria, all with low PAH contamination. Stained sections showed nuclear light-to-dark pink color indicating the presence of PAH-DNA adducts concentrated in intestinal crypt epithelial lining cells. Scoring of whole tissue sections revealed higher values for the 51 SLE beluga, compared with the 20 Arctic and aquarium beluga (P = 0.003). The H-scoring system, applied to coded individual photomicrographs, confirmed that SLE beluga and CI beluga had levels of intestinal PAH-DNA adducts significantly higher than Arctic and aquarium beluga (P = 0.003 and 0.02, respectively). Furthermore, high levels of intestinal PAH-DNA adducts in four SLE beluga with gastrointestinal cancers, considered as a group, support a link of causality between PAH exposure and intestinal cancer in SLE beluga. Environ. Mol. Mutagen. 60:29-41, 2019. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Pseudo-nitzschia, Nitzschia, and domoic acid: New research since 2011

Some diatoms of the genera Pseudo-nitzschia and Nitzschia produce the neurotoxin domoic acid (DA), a compound that caused amnesic shellfish poisoning (ASP) in humans just over 30 years ago (December 1987) in eastern Canada. This review covers new information since two previous reviews in 2012. Nitzschia bizertensis was subsequently discovered to be toxigenic in Tunisian waters. The known distribution of N. navis-varingica has expanded from Vietnam to Malaysia, Indonesia, the Philippines and Australia. Furthermore, 15 new species (and one new variety) of Pseudo-nitzschia have been discovered, bringing the total to 52. Seven new species were found to produce DA, bringing the total of toxigenic species to 26. We list all Pseudo-nitzschia species, their ability to produce DA, and show their global distribution. A consequence of the extended distribution and increased number of toxigenic species worldwide is that DA is now found more pervasively in the food web, contaminating new marine organisms (especially marine mammals), affecting their physiology and disrupting ecosystems. Recent findings highlight how zooplankton grazers can induce DA production in Pseudo-nitzschia and how bacteria interact with Pseudo-nitzschia. Since 2012, new discoveries have been reported on physiological controls of Pseudo-nitzschia growth and DA production, its sexual reproduction, and infection by an oomycete parasitoid. Many advances are the result of applying molecular approaches to discovering new species, and to understanding the population genetic structure of Pseudo-nitzschia and mechanisms used to cope with iron limitation. The availability of genomes from three Pseudo-nitzschia species, coupled with a comparative transcriptomic approach, has allowed advances in our understanding of the sexual reproduction of Pseudo-nitzschia, its signaling pathways, its interactions with bacteria, and genes involved in iron and vitamin B₁₂ and B₇ metabolism. Although there have been no new confirmed cases of ASP since 1987 because of monitoring efforts, new blooms have occurred. A massive toxic Pseudo-nitzschia bloom affected the entire west coast of North America during 2015-2016, and was linked to a 'warm blob' of ocean water. Other smaller toxic blooms occurred in the Gulf of Mexico and east coast of North America. Knowledge gaps remain, including how and why DA and its isomers are produced, the world distribution of potentially toxigenic Nitzschia species, the prevalence of DA isomers, and molecular markers to discriminate between toxigenic and non-toxigenic species and to discover sexually reproducing populations in the field.

Toxoplasma gondii infection in stranded St. Lawrence Estuary beluga Delphinapterus leucas in Quebec, Canada

The St. Lawrence Estuary (SLE) beluga Delphinapterus leucas in Quebec, Canada, is endangered due to intensive hunting in the 19th and 20th centuries and subsequent anthropogenic contamination and human activities in the region. Infectious disease is a primary cause of death in this population. The protozoan parasite Toxoplasma gondii is reported in numerous marine mammal species, including beluga. In the present study, 55 tissue samples (heart and brain) collected from 34 stranded SLE beluga were analysed by PCR followed by DNA sequencing and restriction fragment length polymorphism analysis (RFLP) to determine the PCR prevalence and genotypes of T. gondii in these beluga. Of 34 beluga tested, 44% were positive for T. gondii by PCR, with males having a higher prevalence of infection than females and with more infected neonates and juveniles than adults. Molecular analyses indicated that all T. gondii infecting stranded SLE beluga grouped into genotype II, which predominates in humans. While our results indicate that a high prevalence of stranded beluga are PCR-positive for T. gondii infection, very few deaths are attributed to toxoplasmosis based on published necropsy results. Toxoplasma gondii can cause a range of diseases, including neurological deficits, and more data are needed to investigate this parasite's effect on population recovery.

Genome Sequence of an Alphaherpesvirus from a Beluga Whale (Delphinapterus leucas)

Beluga whale alphaherpesvirus 1 was isolated from a blowhole swab taken from a juvenile beluga whale. The genome is 144,144 bp in size and contains 86 putative genes. The virus groups phylogenetically with members of the genus Varicellovirus in subfamily Alphaherpesvirinae and is the first alphaherpesvirus sequenced from a marine mammal.

INFECTIOUS DISEASE AND TOXICOLOGICAL MONITORING OF STRANDED PACIFIC HARBOR SEALS (PHOCA VITULINA RICHARDSI) IN COOK INLET AS SURROGATES FOR MONITORING ENDANGERED BELUGAS (DELPHINAPTERUS LEUCAS)

  Pacific harbor seals ( Phoca vitulina richardsi) and belugas ( Delphinapterus leucas ) eat many of the same prey species, occupy the same geographic area, and demonstrate site fidelity in Cook Inlet, Alaska. Although most direct research involving the critically endangered belugas is currently prohibited, studying harbor seals may provide important information about this beluga population. In recent years, harbor seal populations in Alaska have declined for unknown reasons. As part of its stranding program, the Alaska SeaLife Center (ASLC) managed 59 cases of live and dead stranded harbor seals from Cook Inlet between 1997 and 2011. Animals were screened for a variety of diseases and contaminants of concern. Animals were negative by serology to the following diseases: avian influenza, canine distemper virus, dolphin morbillivirus, porpoise morbillivirus, Leptospira canicola, L. grippotyphosa, L. pomona, Neospora caninum , Sarcocystis neurona , and Toxoplasma gondii . Positive titers were found against Brucella spp., phocine distemper virus, seal herpesvirus-1, L. bratislava, L. hardjo, and L. icterohemorrhagiae. All titers were stable or declining except in one animal with an increasing titer for seal herpesvirus-1. Fecal pathogen screenings identified normal flora as well as stable or declining low levels of potentially pathogenic and opportunistic bacteria, though most were of little concern for seal health. In most animals, toxicology screening showed that the majority of tested contaminants were below detectable limits. The level of evidence of exposure to pathogens of concern was low in harbor seals. Although the infectious disease burden and contaminant levels in belugas in Cook Inlet cannot be definitively determined without direct testing, pathogen and contaminant exposure is expected to be similar to that found in harbor seals in this region, as the harbor seals and belugas share the habitat and food resources.

Pathologic Findings and Trends in Mortality in the Beluga (Delphinapterus leucas) Population of the St Lawrence Estuary, Quebec, Canada, From 1983 to 2012

An isolated population of beluga (Delphinapterus leucas) inhabits the St Lawrence Estuary, Quebec, Canada. This population has failed to recover despite the prohibition of hunting >30 years ago, suggesting the presence of other limiting factors. The authors summarize the reported causes of death and propose risk factors to explain the lack of recovery of this population. From 1983 to 2012, a total of 472 beluga were found stranded. Complete necropsies were carried out on 222 beluga, including 178 adults, 25 juveniles, and 19 newborn calves. Infectious diseases, the most prevalent cause of mortality in this population, accounted for the death of one-third of all beluga (32%). Verminous pneumonia was the cause of mortality of 13 juvenile beluga (52% of juvenile beluga). A total of 39 malignant neoplasms, diagnosed in 35 beluga, caused the death of 31 beluga (20% of beluga >19 years old). Median age at diagnosis of cancer was 48 years (range, 30-61 years). Dystocia and postpartum complications were the cause of death in 18 beluga, accounting for 19% of the females >19 years old examined. The occurrence of parturition-associated complications, as well as mortality of calves <1 year old, have increased recently in this population and may be the probable cause of the recent decrease in the size of this population. One of the hypotheses proposed to explain the unusually high occurrence of some of the pathologic conditions observed in this population is chronic exposure to environmental contaminants.