Serologic survey for selected virus infections in polar bears at Svalbard

Polar bears (Ursus maritimus) were chemically immobilized and sampled at Svalbard, Norway, and on the pack ice in the Barents Sea from late March to mid-May between 1990 and 1998. Plasma samples were tested for the presence of antibodies to canine distemper virus (CDV), calicivirus, phocid herpesvirus type 1 (PhHV-1), and rabies virus. A seroprevalence of 8% to CDV and 2% to calicivirus were found, whereas no antibodies were detected against PhHV-1 or rabies virus. This serologic survey indicates that polar bears in this region are exposed to morbillivirus and calicivirus, although the nature of these viruses and infections are unknown. Morbillivirus and calicivirus are potential pathogens in seals, but it is unknown whether they may cause health problems in polar bears.     

Serologic survey for Brucella spp., phocid herpesvirus-1, phocid herpesvirus-2, and phocine distemper virus in harbor seals from Alaska, 1976-1999

Harbor seals (Phoca vitulina richardsi) were captured in the coastal regions of Southeast Alaska, Gulf of Alaska, Prince William Sound (PWS), and Kodiak Island during 1976-1999. Blood was collected from 286 seals. Sera were tested for evidence of exposure to Brucella spp., phocid herpesvirus-1 (PhoHV-1), phocid herpesvirus-2 (PhHV-2), and phocine distemper virus (PDV). Antibody prevalence rates were 46% (46/100) for Brucella spp., 93% (225/243) for PhoHV-1, 0% (0/286) for PhHV-2, and 1% (2/160) for PDV. Antibody prevalence for Brucella spp. was directly related to host age. Antibody prevalence for PhoHV-1 was higher in PWS as compared to the other three regions. No evidence of mortality attributable to these four agents was observed during the course of this study. Based on the results of this survey, none of these agents is considered a significant mortality factor in harbor seals from the four regions of coastal Alaska included in the study.     

Antibodies to phocine herpesvirus-1 are common in North American harbor seals (Phoca vitulina)

Phocine herpesvirus-1 (PhHV-1) has been associated with morbidity and high mortality in neonatal harbor seals (Phoca vitulina) along the Pacific coast of California (USA) and in northern Europe. Seals dying with PhHV-1 associated disease in California primarily have histopathologic evidence of adrenal necrosis or adrenalitis with herpesviral inclusion bodies. Little is known about prevalence of exposure to PhHV-1, modes of disease transmission, and viral pathogenesis in free-ranging harbor seal populations. To evaluate the prevalence in North America, 866 serum samples collected between 1994 and 2002 from harbor seals captured or stranded on the Pacific and Atlantic coasts of North America were assayed by enzyme linked immunosorbent assay (ELISA) for evidence of PhHV-1 exposure. Samples from three harbor seal age classes (pre-weaned, weaned, and subadults/adults) were obtained from each of four regions to compare exposure among sex, age class, and region. We found increasing prevalence with age as 37.5% of pre-weaned pups, 87.6% of weaned pups, and 99.0% of subadults and adults were seropositive. When accounting for age, no associations between seropositivity and sex or location of harbor seals were detected. These data indicate that PhHV-1 is endemic in the harbor seal populations of North America.     

Serum chemistry and antibodies against pathogens in antarctic fur seals, Weddell seals, crabeater seals, and Ross seals

Information on health parameters, such as antibody prevalences and serum chemistry that can reveal exposure to pathogens, disease, and abnormal physiologic conditions, is scarce for Antarctic seal species. Serum samples from Antarctic fur seals (Arctocephalus gazella, n=88) from Bouvet?ya (2000-2001 and 2001-2002), and from Weddell seals (Leptonychotes weddellii, n=20), Ross seals (Ommatophoca rossii, n=20), and crabeater seals (Lobodon carcinophagus, n=9) from the pack-ice off Queen Maud Land, Antarctica (2001) were analyzed for enzyme activity, and concentrations of protein, metabolites, minerals, and cortisol. Adult Antarctic fur seal males had elevated levels of total protein (range 64-99 g/l) compared to adult females and pups (range 52-79 g/l). Antarctic fur seals had higher enzyme activities of creatine kinase, lactate dehydrogenase, and amylase, compared to Weddell, Ross, and crabeater seals. Antibodies against Brucella spp. were detected in Weddell seals (37%), Ross seals (5%), and crabeater seals (11%), but not in Antarctic fur seals. Antibodies against phocine herpesvirus 1 were detected in all species examined (Antarctic fur seals, 58%; Weddell seals, 100%; Ross seals, 15%; and crabeater seals, 44%). No antibodies against Trichinella spp., Toxoplasma, or phocine distemper virus (PDV) were detected (Antarctic fur seals were not tested for PDV antibodies). Antarctic seals are challenged by reduced sea ice and increasing temperatures due to climate change, and increased anthropogenic activity can introduce new pathogens to these vulnerable ecosystems and represent a threat for these animals. Our data provide a baseline for future monitoring of health parameters of these Antarctic seal species, for tracking the impact of environmental, climatic, and anthropogenic changes in Antarctica over time.     

Molecular-genetic comparison of morbilliviruses which caused epizooty in Baikal (Phoca siberica) and Caspian (Phoca caspica) seals

The nucleotide sequences were determined for a phosphoprotein gene fragment of canine distemper virus (CDV) by using the RT-PCR method with the subsequent sequencing of amplicons from total RNA isolated from 2 samples of Caspian seals, 15 samples of Baikal seals and from samples of dog's and sea-lion's brains. The above materials were phylogenetically analyzed. The heterogeneity of the virus circulating in the Baikal-seal population was demonstrated. Morbillivirus, that caused epizooty in Caspian seals, was shown to be a CDV variant, whose phosphoprotein gene structure was not different, within the analyzed stretch, from the corresponding gene of the most widespread variant of the Baikal seal virus. The data obtained suggest that morbillivirus could be transmitted by birds during their seasonal migrations.     

Antibodies to human-related H3 influenza A virus in Baikal seals (Phoca sibirica) and ringed seals (Phoca hispida) in Russia

Antibodies to influenza A virus were detected using enzyme-linked immunosorbent assay (ELISA) in the sera from two of seven Baikal seals (Phoca sibrica) and from five of six ringed seals (Phoca hispida) in Russia. In a hemagglutination-inhibition test using H1-H15 reference influenza A viruses, ELISA-positive sera from one Baikal seal and four ringed seals reacted to A/Aichi/2/68 (H3N2) and A/Bangkok/1/79 (H3N2) strains. One ringed seal serum sample reacted to A/seal/Massachusetts/1/80 (H7N7). The present results suggested that human-related H3 viruses were prevalent in Baikal seals and ringed seals inhabiting the central Russian Arctic.     

Seroprevalence of Antibodies against Seal Influenza A(H10N7) Virus in Harbor Seals and Gray Seals from the Netherlands

In the spring and summer 2014, an outbreak of seal influenza A(H10N7) virus infection occurred among harbor seals (Phoca vitulina) off the coasts of Sweden and Denmark. This virus subsequently spread to harbor seals off the coasts of Germany and the Netherlands. While thousands of seals were reported dead in Sweden, Denmark and Germany, only a limited number of seals were found dead in the Netherlands. To determine the extent of exposure of seals in the Netherlands to influenza A/H10N7 virus, we measured specific antibody titers in serum samples from live-captured seals and seals admitted for rehabilitation in the Netherlands by use of a hemagglutination inhibition assay and an ELISA. In harbor seals in 2015, antibodies against seal influenza A(H10N7) virus were detected in 41% (32 out of 78) pups, 10% (5 out of 52) weaners, and 58% (7 out of 12) subadults or adults. In gray seals (Halichoerus grypus) in 2015, specific antibodies were not found in the pups (n = 26), but in 26% (5 out of 19) of the older animals. These findings indicate that, despite apparent low mortality, infection with seal influenza A(H10N7) virus was geographically widespread and also occurred in grey seals.     

The 1988 and 2002 phocine distemper virus epidemics in European harbour seals

We present new and revised data for the phocine distemper virus (PDV) epidemics that resulted in the deaths of more than 23 000 harbour seals Phoca vitulina in 1988 and 30,000 in 2002. On both occasions the epidemics started at the Danish island of Anholt in central Kattegat, and subsequently spread to adjacent colonies in a stepwise fashion. However, this pattern was not maintained throughout the epidemics and new centres of infection appeared far from infected populations on some occasions: in 1988 early positive cases were observed in the Irish Sea, and in 2002 the epidemic appeared in the Dutch Wadden Sea, 6 wk after the initiation of the outbreak at Anholt Island. Since the harbour seal is a rather sedentary species, such 'jumps' in the spread among colonies suggest that another vector species could have been involved. We discussed the role of sympatric species as disease vectors, and suggested that grey seal populations could act as reservoirs for PDV if infection rates in sympatric species are lower than in harbour seals. Alternatively, grey seals could act as subclinical infected carriers of the virus between Arctic and North Sea seal populations. Mixed colonies of grey and harbour seal colonies are found at all locations where the jumps occurred. It seems likely that grey seals, which show long-distance movements, contributed to the spread among regions. The harbour seal populations along the Norwegian coast and in the Baltic escaped both epidemics, which could be due either to genetic differences among harbour seal populations or to immunity. Catastrophic events such as repeated epidemics should be accounted for in future models and management strategies of wildlife populations.     

Serologic study of phocine distemper in a population of harbor seals in Scotland.

A serologic survey of the prevalence of morbillivirus antibodies was conducted in a population of harbor seals (Phoca vitulina) from northeastern Scotland, where mortality was comparatively low during the 1988 phocine distemper virus outbreak. None of the 12 seals sampled before the epizootic were seropositive. Thirty-five (52%) of 68 seals sampled after the beginning of the epizootic were seropositive, although there were significant age-related differences in both the number of seropositive individuals and in antibody levels. Marking studies showed that most seropositive seals caught during the peak of the epizootic survived for several months. Thus, the low mortality observed in this population did not appear to result from a lack of contact with the virus.     

Acute phase protein haptoglobin in blood plasma samples of harbour seals (Phoca vitulina) of the Wadden Sea and of the isle Helgoland

Haptoglobin (Hp) which is synthesized in response to infection, inflammation, trauma or toxicological damage is known as a major acute phase protein in numerous species. Quantification of the circulating concentration of this protein can provide an objective measure of the health status, but there is a lack of investigations on harbour seals. We investigated the Hp concentration in samples of 123 seals (Phoca vitulina) from the German and Danish Wadden Sea to study physiological ranges of Hp levels. Hp levels between 2002, the end of the phocine distemper virus epidemic (PDV), and 2007 were considered, and Hp concentrations between animals of different sex, ages as well as living areas were compared. Furthermore, as a case study, six animals from the open sea isle Helgoland were investigated in 2006. Influences on the health status of the seal population e.g. the PDV epidemic were reflected by increased Hp levels in North Sea seals in 2002. The results of the Wadden Sea seals showed no significant age-, sex-, or geographical area-related differences. Interestingly, for the seals of the open sea isle Helgoland higher Hp values were measured compared to the Wadden Sea seals. The present study demonstrates that Hp can be used as a diagnostic tool to monitor the health status of harbour seals.     

PHOCINE DISTEMPER VIRUS INFECTION IN HARP SEALS (PHOCA GROENLANDICA)

Antibodies against phocine distemper virus were found in liver and serum specimens of harp seals from the Barents Sea and north of Jan Mayen (West Ice) in 1987 and 1989. By immunoperoxidase testing, antibodies against phocine distemper virus could be demonstrated in 34 of 74 liver specimens (46%) from 1987 and in 44 of 126 liver specimens (35%) from 1989. The prevalence of neutralizing serum antibodies against phocine distemper virus was found to be 98% in 1989. Both findings clearly demonstrate the presence of a widespread infection with phocine distemper virus or a closely related virus in harp seals. The significance of these findings to the recent outbreak of phocine distemper virus infection in harbor seals in Northwestern Europe is discussed and it is concluded that there may be an epizootiological link between this outbreak and the large migration of harp seals in 1987.     

Quantitative assessment of species identification in aerial transect surveys for ice‐associated seals

Technological advances have facilitated collection of vast quantities of photographic data from aerial surveys of marine mammals. However, when it is difficult to distinguish species from a distance, reliable identification from aerial images can often be challenging. This is the case for ice‐associated seals, species for which global climate change has motivated intensive monitoring efforts in recent years. We assess species and age class identification from aerial images of four ice seal species (bearded seals, Erignathus barbatus; ribbon seals, Histriophoca fasciata; ringed seals, Pusa hispida; spotted seals, Phoca largha) in the Bering Sea. We also investigate the specific phenomenological and behavioral traits commonly associated with species identification and observer confidence. We generally found species and age class misidentification occurred at relatively low levels, but only 83% of spotted seals tended to be correctly identified (with 11% mistaken as ribbon seals). We also found certain traits were strong predictors for observed species, age class, or observer confidence. Our findings add to the growing body of evidence that species misidentification is pervasive in passive sampling of animal populations. Even low levels of misidentification have been demonstrated to induce substantial biases in estimators of species distribution and abundance, and it is important that statistical models account for such errors.     

Identification of hairs found in leopard seal (<Emphasis Type="Italic">Hydrurga leptonyx</Emphasis>) scats

The leopard seal is a top-order predator in the Southern Ocean ecosystem and preys on a wide variety of vertebrate species including seals and penguins. We assessed the use of hairs found in leopard seal scats to identify the species of pinniped consumed. A reference collection of hairs was obtained from four potential leopard seal prey species including crabeater, Weddell, Ross, and Southern elephant seals. Discrimination techniques applied to terrestrial mammals did not allow for identification of the seal hairs. Instead, a 2-dimensional (2-D) and 6-dimensional (6-D) analysis technique utilising Mahalanobis distances (D ²) was used. The smallest Mahalanobis distance together with the largest value of p(F) positively identified hairs from each species. The 6-D analysis was more accurate and applied to hairs found in the leopard seal scats. The majority of prey species were identified as crabeater seals, which are a known prey item of the leopard seal.     

Temporal variation in distribution and density of ice-obligated seals in western Hudson Bay, Canada

Recent unidirectional climatic trends and changes in top predator population ecology suggest that long-term modifications may be happening in Hudson Bay, Canada. Effects of such changes on ice-obligated seal populations are expected but long-term studies are required to differentiate climate-induced changes from natural variation. We conducted strip-transect surveys in late spring in 1995–1997, 1999–2000 and 2007–2008 to estimate distribution, density and abundance of ice-obligated ringed (Phoca hispida) and bearded (Erignathus barbatus) seals in western Hudson Bay. When hauled out, ringed seals preferred land-fast and consolidated pack ice, whereas bearded seals preferred unconsolidated pack ice. Bearded and ringed seal density estimates varied from 0.0036 to 0.0229 seals/km² of ice and from 0.46 to 1.60 seals/km² of ice, respectively. Strong inter-annual variations were recorded in the abundance estimates of both species, with the largest abundance estimates in 1995 (104,162 and 1,494 ringed and bearded seals, respectively) and the lowest in 2008 for ringed seals (33,701) and 1997 for bearded seals (278). A sine function best described seal density estimates in western Hudson Bay and suggested a decadal cycle. Previous studies that reported low ringed seal demographic parameters in the 1990s and a recovery in the 2000s supported our interpretation of the survey results. We discuss our results in the context of climate warming and suggest that a long-term decline in ice-obligated seal density estimates may overlay a possible natural decadal cycle.     

Characterization of Otostrongylus circumlitus from Pacific harbor and northern elephant seals

Otostrongylus circumlitus (Railliet, 1899) from Pacific harbor seals (Phoca vitulina richardsi) and northern elephant seals (Mirounga angustirostris) were examined using morphological and molecular methods to determine whether northern elephant seals along the central California coast are infected by the same species of Otostrongylus as are Pacific harbor seals in the same area. Fixed nematodes were examined and measured using light microscopy. The polymerase chain reaction (PCR) was used to amplify and sequence the second internal transcribed spacer (ITS-2) and D3 expansion (26S) regions of ribosomal DNA of O. circumlitus from Pacific harbor and northern elephant seals. The ITS-2 region was also amplified from Parafilaroides sp. from the Pacific harbor seal, northern elephant seal, and California sea lion (Zalophus californianus) and used for restriction fragment length polymorphism (RFLP) analysis. Morphologically, it was not possible to distinguish O. circumlitus from Pacific harbor and northern elephant seals, and over a consensus length of 443 base pairs (bp) for ITS-2 and 321 bp for D3 the sequences of O. circumlitus from both hosts were identical. With the PCR-RFLP assay, it was possible to distinguish O. circumlitus from Parafilaroides sp. The results suggest that O. circumlitus is the same species in Pacific harbor and northern elephant seals, and molecular methods make it possible to distinguish this nematode from related nematodes.     

Serological evidence of transmission of human influenza A and B viruses to Caspian seals (Phoca caspica)

Seroepidemiological surveillance of influenza in Caspian seals (Phoca caspica) was conducted. Antibodies to influenza A virus were detected in 54% (7/13), 57% (4/7), 40% (6/15) and 26% (11/42) of the serum samples collected in 1993, 1997, 1998 and 2000 by enzyme-linked immunosorbent assay (ELISA). In an hemagglutination-inhibition (HI) test using H1-H15 reference influenza A viruses as antigens, more than half of the examined ELISA-positive sera reacted with an H3N2 prototype strain A/Aichi/2/68. These sera were then examined by HI test with a series of naturally occurring antigenic variants of human H3N2 virus, and H3 viruses of swine, duck, and equine origin. The sera reacted strongly with the A/Bangkok/1/79 (H3N2) strain, which was prevalent in humans in 1979-1981. The present results indicate that human A/Bangkok/1/79-like virus was transmitted to Caspian seals probably in the early 1980s, and was circulated in the population. Antibodies to influenza B virus were detected by ELISA in 14% (1/7) and 10% (4/42) serum samples collected from Caspian seals in 1997 and 2000, respectively. Our findings indicate that seal might be a reservoir of both influenza A and B viruses originated from humans.     

Variation in blubber fatty acid composition among marine mammals in the Canadian Arctic

The composition of predator adipose stores can provide important insights into foraging patterns and the ecological relationships among species. We determined the fatty acid (FA) composition of 843 blubber samples from 80 bearded seals (Erignathus barbatus), 33 harbor seals (Phoca vitulina), 239 harp seals (Pagophilus groenlandicus), 32 hooded seals (Cystophora cristata), 281 ringed seals (Phoca hispida), 53 walruses (Odobenus rosmarus rosmarus), 105 beluga whales (Delphinapterus leucas), and 20 narwhals (Monodon monoceros) across the Canadian Arctic to examine patterns of variability among and within species. FA signatures accurately distinguished phocid seals, walruses, and whales. Belugas and narwhals had the most similar FA signatures of any two species, suggesting substantial overlap in their diets, especially in the narwhal‐wintering area off eastern Baffin Island. Among phocid seals, harp and hooded seals had the most similar FA signatures. Bearded seals were most similar to walruses, which was consistent with the benthic feeding habits of both species. Within species, geographic differences in FA signatures were found over both large (>4,000 km) and small (<100 km) spatial scales. Overall, within‐species differences were smaller than among‐species differences. In general, FA signature patterns were consistent with previous studies of the ecology and diets of arctic marine mammals.     

Long-term monitoring of Antarctic pinnipeds in Admiralty Bay (South Shetlands, Antarctica)

Year-round monitoring of five Antarctic pinnipeds was conducted in Admiralty Bay from 1988 up to 2000. Two breeding species: southern elephant sealsMirounga leonina (Linnaeus, 1758) and Weddell sealsLeptonychotes weddellii (Lesson, 1826), were present throughout the year. Three other species: crabeater seals Lobodon carcinophagus (Hobron and Jacquinot, 1842), leopard sealsHydrurga leptonyx (Blainville, 1820), and Antarctic fur sealsArctocephalus gazella (Peters, 1875) visited the area only for short periods. During this study, the abundance of elephant seals was stable, whereas those of Weddell and crabeater seals declined. Leopard seals numbers fluctuated irregularly. We detected a possible immigration from South Georgia: of a stable magnitude for elephant seals, and of variable magnitude, depending on food accessibility, for Antarctic fur seals. We found a strong recurrence of the spatial distributions of elephant, Weddell, and Antarctic fur seals in the 13 oases on the shore of Admiralty Bay. Annual distribution patterns were characteristic for each species. The innermost beaches were used predominantly by the animals during their annual fasts: the breeding and the moulting seasons.     

Comparison of Helicobacter spp. genetic sequences in wild and captive seals, and gulls

Helicobacter species are widely distributed in the gastrointestinal system of humans and many animal taxa. Investigations of natural infections are essential to elucidating their role within the host. The feces of fur seals Arctocephalus pusillus doriferus and sea lions Neophoca cinerea from 3 separate captive populations, as well as a wild colony from Kangaroo Island, Australia, were examined for the occurrence of Helicobacter spp. The feces from several wild silver gulls Larus novahollandiae were also investigated. As detected by PCR, 18 of 21 samples from captive and 12 of 16 samples from wild seals were positive for Helicobacter spp. Three species were identified in these animals. Whilst one possibly novel type was identified from wild fur seals, the majority of wild and captive individuals had the same species. This species also occurred in more than 1 seal type and in silver gulls, and shared a 98.1 to 100% identity to other Helicobacter spp. from harp seals and sea otters. A similar sequence type to species identified from cetaceans was also detected in several captive seals. This study reports for the first time the presence of Helicobacter spp. in wild and captive seals and demonstrates the diversity and broad-host range of these organisms in the marine host.