Pathological Findings in Harbour Seals ( Phoca vitulina ): 1996–2005

Heartworm and seal louse: Trends in prevalence, characterisation of impact and transmission pathways in a unique parasite assembly on seals in the North and Baltic Sea

The ectoparasitic seal louse, Echinophthirius horridus infects harbour (Phoca vitulina) and grey seals (Halichoerus grypus) in the North and Baltic Sea. The endoparasitic heartworm Acanthocheilonema spirocauda parasitizes the right heart and blood vessels of harbour seals. The complete lifecycle of the heartworm is not entirely understood although the seal louse is assumed to serve as vector for its transmission. Knowledge about the impact of both parasite species on host health are scarce. In this study, necropsy data and archived parasites of harbour and grey seals in German waters were analysed to determine long-term seal louse (SLP) and heartworm prevalence (HWP) from 2014 to 2021. Histology, microbiology and scanning electron microscopy (SEM) were applied on seal louse infected and uninfected skin to investigate associated lesions and the health impact. During the study period, HWP in harbour seals was 13%, the SLP in harbour seals was 4% and in grey seals 10%. HWP of harbour seals was significantly higher during the winter months compared to the summer. SLP in adults was significantly higher in comparison to juvenile harbour seals. SLP varied significantly between grey seals from the North and Baltic Sea. Filarial nematodes were detected in the haemocoel, pharynx, and intestine of E. horridus highlighting the seal louse as vector for heartworms. Alopecia and folliculitis were associated with the attachment posture of E. horridus and microbiological investigations isolated bacteria commonly associated with folliculitis.

Attachment performance of the ectoparasitic seal louse Echinophthirius horridus

Marine mammals host a great variety of parasites, which usually co-evolved in evolutionary arms races. However, little is known about the biology of marine mammal insect parasites, and even less about physical aspects of their life in such a challenging environment. One of 13 insect species that manage to endure long diving periods in the open sea is the seal louse, Echinophthirius horridus, parasitising true seals. Its survival depends on its specialised adaptations for enduring extreme conditions such as hypoxia, temperature changes, hydrostatic pressure, and strong drag forces during host dives. To maintain a grip on the seal fur, the louse's leg morphology is equipped with modified snap hook claws and soft pad-like structures that enhance friction. Through techniques including CLSM, SEM, and histological staining, we have examined the attachment system's detailed structure. Remarkably, the seal louse achieves exceptional attachment forces on seal fur, with safety factors (force per body weight) reaching 4500 in average measurements and up to 18000 in peak values, indicating superior attachment performance compared to other insect attachment systems. These findings underscore the louse's remarkable adaptations for life in a challenging marine environment, shedding light on the relationship between structure and function in extreme ecological niches.

Loss of species and genetic diversity during colonization: Insights from acanthocephalan parasites in northern European seals

Studies on host-parasite systems that have experienced distributional shifts, range fragmentation, and population declines in the past can provide information regarding how parasite community richness and genetic diversity will change as a result of anthropogenic environmental changes in the future. Here, we studied how sequential postglacial colonization, shifts in habitat, and reduced host population sizes have influenced species richness and genetic diversity of Corynosoma (Acanthocephala: Polymorphidae) parasites in northern European marine, brackish, and freshwater seal populations. We collected Corynosoma population samples from Arctic, Baltic, Ladoga, and Saimaa ringed seal subspecies and Baltic gray seals, and then applied COI barcoding and triple-enzyme restriction-site associated DNA (3RAD) sequencing to delimit species, clarify their distributions and community structures, and elucidate patterns of intraspecific gene flow and genetic diversity. Our results showed that Corynosoma species diversity reflected host colonization histories and population sizes, with four species being present in the Arctic, three in the Baltic Sea, two in Lake Ladoga, and only one in Lake Saimaa. We found statistically significant population-genetic differentiation within all three Corynosoma species that occur in more than one seal (sub)species. Genetic diversity tended to be high in Corynosoma populations originating from Arctic ringed seals and low in the landlocked populations. Our results indicate that acanthocephalan communities in landlocked seal populations are impoverished with respect to both species and intraspecific genetic diversity. Interestingly, the loss of genetic diversity within Corynosoma species seems to have been less drastic than in their seal hosts, possibly due to their large local effective population sizes resulting from high infection intensities and effective intra-host population mixing. Our study highlights the utility of genomic methods in investigations of community composition and genetic diversity of understudied parasites.

The prevalence of Corynosoma parasite worms in the great cormorants and the Baltic herring in the northern Baltic Sea, Finland

During 2014-2019, the prevalence of Corynosoma spp., a parasite species in great cormorants (Phalacrocorax carbo spp.) and in Baltic herring (Clupea harengus membras), was studied in the Archipelago and the Bothnian Seas of the northern Baltic Sea. These results suggest that cormorants may act as a definitive host for these acanthocephalan parasites. Adults were more infected with the parasites than juveniles, which could be due to their larger size. A lower prevalence of Corynosoma spp. in juveniles may be because smaller cormorants eat smaller fish that have less parasites. We found that the most abundant corynosoma species in both the Baltic herring and cormorants were Corynosoma semerme, whereas only a few individuals of C. strumosum and only one C. magdaleni were found. The prevalence of corynosoma in herring increased from 2014 to 2018, and individuals in the Bothnian Sea were infected less frequently than herring in the Archipelago Sea. Results also showed that infected herring individuals were generally larger than non-infected individuals, which could be explained by their size and their feeding habits. Currently, the changing environment of the Baltic Sea may cause an effect on the herring making them more susceptible to infections. Our results, therefore, emphasize the importance of the regular monitoring of infections and the parasite-host relationships in the Baltic Sea.

Heartworms in Halichoerus grypus: first records of Acanthocheilonema spirocauda (Onchocercidae; Filarioidea) in 2 grey seals from the North Sea

The assumed definitive host of the heartworm Acanthocheilonema spirocauda (Onchocerdidae; Filarioidea) is the harbour seal (Phoca vitulina). This filaroid nematode parasitizing in cardiac ventricles and blood vessel lumina of harbour seals (P. vitulina) has a low prevalence and seldom causes severe health impacts. The seal louse (Echinophthirius horridus) is the assumed intermediate host for transmission of A. spirocauda filariae between seals, comprising a unique parasite assembly conveyed from the terrestrial ancestors of pinnipeds. Although grey seals (Halichoerus grypus) are infected by seal lice, heartworm infection was not verified. Analysing a longterm dataset compiled over decades (1996–2021) of health monitoring seals along the German coasts comprising post mortem investigations and archived parasites, 2 cases of A. spirocauda infected male grey seals were detected. Tentative morphological identification was confirmed with molecular tools by sequencing a section of mtDNA COI and comparing nucleotide data with available heartworm sequence. This is the first record of heartworm individuals collected from the heart of grey seals at necropsy. It remains puzzling why heartworm infection occur much less frequently in grey than in harbour seals, although both species use the same habitat, share mixed haul-outs and consume similar prey species. If transmission occurs directly via seal louse vectors on haul-outs, increasing seal populations in the North- and Baltic Sea could have density dependent effects on prevalence of heartworm and seal louse infections. It remains to be shown how species-specificity of filarial nematodes as well as immune system traits of grey seals influence infection patterns of A. spirocauda.

Dirofilaria immitis Identified in Galapagos Sea Lions (Zalophus wollebaeki): A Wildlife Health and Conservation Concern

The Galapagos sea lion (Zalophus wollebaeki), an endemic and endangered pinniped, faces an increasing threat due to infectious diseases related to domestic animals. Dirofilaria immitis, the parasite responsible for canine heartworm disease, is one such threat, as canine infections on the archipelago have been documented. We used a canine heartworm antigen test kit to analyze the blood from 25 juvenile Galapagos sea lions for D. immitis. Two (8%) sea lions tested positive for D. immitis antigen. Using morphologic and genetic assessments, we evaluated 20 filarial-like worms collected from within the heart of an adult male Galapagos sea lion during a previous routine postmortem examination. The intracardiac worms were morphologically consistent with adult D. immitis, and sequence analysis of targeted PCR amplicons confirmed their identity. This is the first report of D. immitis infection in Galapagos sea lions, which could become a major health problem for these pinnipeds. Further studies are necessary to confirm the level of threat from this parasite; however, widespread adoption of routine heartworm testing, prevention, and treatment in the canine population, and the control of mosquitos, could potentially reduce the disease impact on this endangered pinniped species.

Bone mineral density and microarchitecture change during skeletal growth in harbor seals (Phoca vitulina) from the German coast

Across species, the skeletal system shares mutual functions, including the protection of inner organs, structural basis for locomotion, and acting as an endocrine organ, thus being of pivotal importance for survival. However, insights into skeletal characteristics of marine mammals are limited, especially in the growing skeleton. Harbor seals (Phoca vitulina) are common marine mammals in the North and Baltic Seas and are suitable indicators of the condition of their ecosystem. Here, we analyzed whole-body areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry (DXA) and lumbar vertebrae by high-resolution peripheral quantitative computed tomography (HR-pQCT) in neonate, juvenile, and adult harbor seals. Along skeletal growth, an increase in two-dimensional aBMD by DXA was paralleled by three-dimensional volumetric BMD by HR-pQCT, which could be attributed to an increasing trabecular thickness while trabecular number remained constant. Strong associations were observed between body dimensions (weight and length) and aBMD and trabecular microarchitecture (R² = 0.71-0.92, all p < 0.001). To validate the results of the DXA measurement (i.e., the standard method used worldwide to diagnose osteoporosis in humans), we performed linear regression analyses with the three-dimensional measurements from the HR-pQCT method, which revealed strong associations between the two imaging techniques (e.g., aBMD and Tb.Th: R² = 0.96, p < 0.0001). Taken together, our findings highlight the importance of systematic skeletal investigations in marine mammals during growth, illustrating the high accuracy of DXA in this context. Regardless of the limited sample size, the observed trabecular thickening is likely to represent a distinct pattern of vertebral bone maturation. As differences in nutritional status, among other factors, are likely to affect skeletal health, it appears essential to routinely perform skeletal assessments in marine mammals. Placing the results in the context of environmental exposures may allow effective measures to protect their populations.

Potential new species of pseudaliid lung nematode (Metastrongyloidea) from two stranded neonatal orcas (Orcinus orca) characterized by ITS-2 and COI sequences

Knowledge about parasite species of orcas, their prevalence, and impact on the health status is scarce. Only two records of lungworm infections in orca exist from male neonatal orcas stranded in Germany and Norway. The nematodes were identified as Halocercus sp. (Pseudaliidae), which have been described in the respiratory tract of multiple odontocete species, but morphological identification to species level remained impossible due to the fragile structure and ambiguous morphological features. Pseudaliid nematodes (Metastrongyloidea) are specific to the respiratory tract of toothed whales and are hypothesized to have become almost extinct in terrestrial mammals. Severe lungworm infections can cause secondary bacterial infections and bronchopneumonia and are a common cause of mortality in odontocetes. DNA isolations and subsequent sequencing of the rDNA ITS-2 and mtDNA COI revealed nucleotide differences between previously described Halocercus species from common dolphin (H. delphini) and harbor porpoises (H. invaginatus) that were comparatively analyzed, pointing toward a potentially new species of pseudaliid lungworm in orcas. New COI sequences of six additional metastrongyloid lungworms of seals and porpoises were derived to elucidate phylogenetic relationships and differences between nine species of Metastrongyloidea.

Screening for Influenza and Morbillivirus in Seals and Porpoises in the Baltic and North Sea

Historically, the seals and harbour porpoises of the Baltic Sea and North Sea have been subjected to hunting, chemical pollutants and repeated mass mortalities, leading to significant population fluctuations. Despite the conservation implications and the zoonotic potential associated with viral disease outbreaks in wildlife, limited information is available on the circulation of viral pathogens in Baltic Sea seals and harbour porpoises. Here, we investigated the presence of the influenza A virus (IAV), the phocine distemper virus (PDV) and the cetacean morbillivirus (CeMV) in tracheal swabs and lung tissue samples from 99 harbour seals, 126 grey seals, 73 ringed seals and 78 harbour porpoises collected in the Baltic Sea and North Sea between 2002–2019. Despite screening 376 marine mammals collected over nearly two decades, we only detected one case of PDV and two cases of IAV linked to the documented viral outbreaks in seals in 2002 and 2014, respectively. Although we find no evidence of PDV and IAV during intermediate years, reports of isolated cases of PDV in North Sea harbour seals and IAV (H5N8) in Baltic and North Sea grey seals suggest introductions of those pathogens within the sampling period. Thus, to aid future monitoring efforts we highlight the need for a standardized and continuous sample collection of swabs, tissue and blood samples across Baltic Sea countries.

Status of Infectious Diseases in Free-Ranging European Brown Hares (Lepus europaeus) Found Dead between 2017 and 2020 in Schleswig-Holstein, Germany

The European brown hare (Lepus europaeus) is a quite adaptable species, but populations have been decreasing for several decades in different countries, including Germany. To investigate infectious diseases as possible influences on observed population decline in the German federal state Schleswig-Holstein, 118 deceased free-ranging European brown hares were collected between 2017 and 2020 and underwent detailed postmortem examination with extended sampling. Infectious diseases were a major cause of death (34.7%). The number of juveniles found exceeded the adult ones. The main pathomorphological findings were hepatitis (32.8%), pneumonia (22.2%), nephritis (19.1%), liver necrosis (12.9%), and enteritis (40.7%). An unusual main finding was steatitis (20.9%) of unknown origin. Animals were mainly emaciated and showed high infection rates with Eimeria spp. (91.3%) and Trichostrongylus spp. (36.2%). European Brown Hare Syndrome Virus reached an epidemic status with few fatal infections (4.2%) and high seroprevalence (64.9%), whereas the prevalence of Rabbit Haemorrhagic Disease Virus 2 was very low (0.8%) in hares in Schleswig-Holstein. Pathogens such as Yersinia pseudotuberculosis (5.9%), Pasteurella multocida (0.8%), and Staphylococcus aureus (3.4%) only caused sporadic deaths. This study illustrates the wide distribution of various infectious pathogens with high mortality and even zoonotic potential. Infectious diseases need to be considered as an important influence on population dynamics in Schleswig-Holstein.

Verminotic pneumonia in South American fur seal (Arctocephalus australis) in Southern Brazil

Verminotic pneumonia caused by Parafilaroides spp. nematodes is an underreported disease in beached South American fur seals, with scant literature available on the characteristics of parafilaroidiasis, the nematode itself, as well as its occurrence in pinnipeds in Brazil. The present work aims to identify, describe and detail the histological features of the infection and molecular characteristics of verminotic pneumonia in the South American fur seal. Twenty-six specimens of Arctocephalus australis, found dead on the northern coast of Rio Grande do Sul in 2021, were analysed. These animals were identified and submitted to necropsy and histology. For the molecular identification of metastrongylids, lung fragments were subjected to DNA extraction, polymerase chain reaction targeting the Internal transcribed spacer 2 (ITS-2) gene and subsequent sequencing. In total, 12 animals presented with parasites in the lung parenchyma on histological evaluation, and only 1 showed a granulomatous lung lesion at necropsy. Microscopically, the nematodes were found mainly in the alveoli, associated with little or no inflammatory response, and they had morphological characteristics compatible with metastrongylids. Six ITS-2 gene quality sequences were obtained; after comparative analysis via BLAST, they showed similarity with sequences obtained from Parafilaroides sp. Therefore, verminotic pneumonia caused by Parafilaroides represents an important differential diagnosis of lung disease in South American fur seals found on the northern coast of Rio Grande do Sul.

Variation of blubber thickness for three marine mammal species in the southern Baltic Sea

Evaluating populational trends of health condition has become an important topic for marine mammal populations under the Marine Strategy Framework Directive (MSFD). In the Baltic Sea, under the recommendation of Helsinki Commission (HELCOM), efforts have been undertaken to use blubber thickness as an indicator of energy reserves in marine mammals. Current values lack geographical representation from the entire Baltic Sea area and a large dataset is only available for grey seals (Halichoerus grypus) from Sweden and Finland. Knowledge on variation of blubber thickness related to geography throughout the Baltic Sea is important for its usage as an indicator. Such evaluation can provide important information about the energy reserves, and hence, food availability. It is expected that methodological standardization under HELCOM should include relevant datasets with good geographical coverage that can also account for natural variability in the resident marine mammal populations. In this study, seasonal and temporal trends of blubber thickness were evaluated for three marine mammal species-harbor seal (Phoca vitulina), grey seal (Halichoerus grypus) and harbor porpoise (Phocoena phocoena)-resident in the southern Baltic Sea collected and investigated under stranding networks. Additionally, the effects of age, season and sex were analyzed. Seasonal variation of blubber thickness was evident for all species, with harbor seals presenting more pronounced effects in adults and grey seals and harbor porpoises presenting more pronounced effects in juveniles. For harbor seals and porpoises, fluctuations were present over the years included in the analysis. In the seal species, blubber thickness values were generally higher in males. In harbor seals and porpoises, blubber thickness values differed between the age classes: while adult harbor seals displayed thicker blubber layers than juveniles, the opposite was observed for harbor porpoises. Furthermore, while an important initial screening tool, blubber thickness assessment cannot be considered a valid methodology for overall health assessment in marine mammals and should be complemented with data on specific health parameters developed for each species.

Occurrence of Antimicrobial-Resistant Escherichia coli in Marine Mammals of the North and Baltic Seas: Sentinels for Human Health

Antimicrobial resistance is a global health threat that involves complex, opaque transmission processes in the environment. In particular, wildlife appears to function as a reservoir and vector for antimicrobial-resistant bacteria as well as resistance genes. In the present study, the occurrence of antimicrobial-resistant Escherichia coli was determined in marine mammals and various fish species of the North and Baltic Seas. Rectal or faecal swabs were collected from 66 live-caught or stranded marine mammals and 40 fish specimens. The antimicrobial resistance phenotypes and genotypes of isolated E. coli were determined using disk diffusion tests and PCR assays. Furthermore, isolates were assigned to the four major phylogenetic groups of E. coli. Additionally, post mortem examinations were performed on 41 of the sampled marine mammals. The investigations revealed resistant E. coli in 39.4% of the marine mammal samples, while no resistant isolates were obtained from any of the fish samples. The obtained isolates most frequently exhibited resistance against aminoglycosides, followed by β-lactams. Of the isolates, 37.2% showed multidrug resistance. Harbour porpoises (Phocoena phocoena) mainly carried E. coli isolates belonging to the phylogenetic group B1, while seal isolates were most frequently assigned to group B2. Regarding antimicrobial resistance, no significant differences were seen between the two sampling areas or different health parameters, but multidrug-resistant isolates were more frequent in harbour porpoises than in the sampled seals. The presented results provide information on the distribution of antimicrobial-resistant bacteria in the North and Baltic Seas, and highlight the role of these resident marine mammal species as sentinels from a One Health perspective.

Primary harbor seal (Phoca vitulina) airway epithelial cells show high susceptibility to infection by a seal-derived influenza A virus (H5N8)

Highly pathogenic avian influenza viruses of the H5N8 subtype have been circulating in Europe and Asia since 2016, causing huge economic losses to the poultry industry. A new wave of H5Nx infections has begun in 2020. The viruses mainly infect wild birds and waterfowl; from there they spread to poultry and cause disease. Previous studies have shown that the H5N8 viruses have seldom spread to mammals; however, reports in early 2021 indicate that humans may be infected, and some incident reports indicate that H5Nx clade 2.3.4.4B virus may be transmitted to wild mammals, such as red foxes and seals. In order to get more information on how the H5N8 virus affects seals and other marine animals, here, we used primary cultures to analyze the cell tropism of the H5N8 virus, which was isolated from an infected gray seal (H5N8/Seal-2016). Primary tracheal epithelial cells were readily infected by H5N8/Seal -2016 virus; in contrast, the commonly used primary seal kidney cells required the presence of exogenous trypsin to initiate virus infection. When applied to an ex vivo precision-cut lung slice model, compared with recombinant human H3N2 virus or H9N2 LPAI virus, the H5N8/Seal-2016 virus replicated to a high titer and caused a strong detrimental effect; with these characteristics, the virus was superior to a human H3N2 virus and to an H9N2 LPAI virus. By using well-differentiated air-liquid interface cultures, we have observed that ALI cultures of canines, ferrets, and harbor seals are more sensitive to H5N8/Seal-2016 virus than are human or porcine ALI cultures, which cannot be fully explained by sialic acid distribution. Our results indicate that the airway epithelium of carnivores may be the main target of H5N8 viruses. Consideration should be given to an increased monitoring of the distribution of highly pathogenic avian influenza viruses in wild animals. This article is protected by copyright. All rights reserved.

Occurrence of Microplastics in Harbour Seals (Phoca vitulina) and Grey Seals (Halichoerus grypus) from German Waters

The level of knowledge on microplastic exposure in marine mammals is limited by the access to dead and alive individuals. Focusing on the Northeast Atlantic area, some studies already confirmed the microplastic presence in free-ranging marine mammals, such as harbour porpoises or harbour seals inhabiting the North Sea (NS). In contrast, knowledge on the exposure to grey seals and particularly on specimen inhabiting the Baltic Sea (BS) are scarce. This study examined 63 gastrointestinal tracts (GIT) of harbour seals and grey seals originating from German waters (NS and BS) found between 2014 and 2019. Besides the documentation of microplastic findings, this study is dealing with life history and health parameters, attempting to identify correlations with microplastic presence. This study confirmed beside the presence, the egestion of microplastics (>100 µm; MPs) in the examined seals, without correlations in parasite infestations or inflammation responses. 540 suspected MPs were identified in 62 intestinal samples (42% fibres, 58% fragments), and 228 MPs in seven stomachs (28% fibres, 72% fragments). In accordance, first evidence of the retainment of fragments in the GIT were given. However, no significant difference in MP occurrence was indicated for different sex or age groups.

Relationships between gene transcription and contaminant concentrations in Baltic ringed seals: A comparison between tissue matrices

Ringed seals (Pusa hispida) are slowly recovering in the eastern and northern parts of the Baltic Sea after years of hunting pressure and contaminant exposure. Still, consequences of anthropogenic activities such as contaminant exposure and increasing temperatures are stressors that continue to have deleterious effects on their habitat and health. Transcription profiles of seven health-related genes involved in xenobiotic metabolism, endocrine disruption and stress were evaluated in blood, blubber, and liver of Baltic ringed seals in a multi-tissue approach. Selected persistent organic pollutants and total mercury concentrations were measured in blubber and liver, and muscle and liver of these animals, respectively. Concentrations of contaminants varied across tissues on a lipid weight basis but not with sex. mRNA transcript levels for all seven target genes did not vary between sexes or age classes. Transcript levels of thyroid hormone receptor alpha (TRα), retinoic acid receptor alpha (RARα) and heat shock protein 70 (HSP70) correlated with levels of persistent organic pollutants. TRα transcript levels also correlated positively with mercury concentrations in the liver. Of the three tissues assessed in this multi-tissue approach, blubber showed highest transcription levels of aryl hydrocarbon receptor nuclear translocator (ARNT), thyroid stimulating hormone receptor beta (TSHβ), oestrogen receptor alpha (ESR1) and peroxisome proliferator activated receptor alpha (PPARα). The wide range of genes expressed highlights the value of minimally invasive sampling (e.g. biopsies) for assessing health endpoints in free-ranging marine wildlife and the importance of identifying optimal matrices for targeted gene expression studies. This gene transcript profile study has provided baseline information on transcript levels of biomarkers for early on-set health effects in ringed seals and will be a useful guide to assess the impacts of environmental change in Baltic pinnipeds for conservation and management.

Pathological Findings in Eurasian Otters (Lutra lutra) Found Dead between 2015-2020 in Schleswig-Holstein, Germany

In times of massive biodiversity loss and ongoing environmental crises, it is extremely important to ensure long-term conservation efforts of threatened species like Eurasian otters (Lutra lutra). To gain insights into the status of Northern Germany's otter population, 92 otters found dead in Schleswig-Holstein between 2015-2020 were collected and underwent detailed dissection with the aim to establish a monitoring program for this population. Examinations followed a protocol especially designed for otters, including various biological data assessments and extended sampling. The finding sites showed a clear concentration in the Continental region. Seasonal concentration differed among the years, yet peaks were seen from fall to winter. Overall, more males than females were found, although this differed among the years. The majority of otters that could be aged were between 1-3 years. Placental scars and pregnancy were recorded in only few females. Nutritional status was good in most cases. Infectious diseases found included Vagococcus lutrae, Toxoplasma gondii, and Emmonsia spp. A major cause of death was roadkill. Known sample bias in studies focusing on roadkill was considered in the finding interpretation. Continuation of the population health investigations is mandatory to analyze potential trends and to establish an actual monitoring program for Eurasian otters in Schleswig-Holstein.

Whale lice (Isocyamus deltobranchium & Isocyamus delphinii; Cyamidae) prevalence in odontocetes off the German and Dutch coasts - morphological and molecular characterization and health implications

Whale lice (Cyamidae; Amphipoda) are ectoparasitic crustaceans adapted to the marine environment with cetaceans as their host. There are few reports of cyamids occurring in odontocetes from the North Sea, and long-term studies are lacking. Marine mammal health was monitored along the German and Dutch coasts in the past decades, with extensive post mortem investigations conducted. The aim of this study was to analyse archived ectoparasite samples from stranded cetaceans from the North Sea (2010-2019), to determine species, prevalence and impact of ectoparasite infection. Ectoparasites were found on two cetacean species - harbour porpoises (Phocoena phocoena), as the most abundant cetacean species in the North Sea, and on a pilot whale (Globicephala melas), as a rare species here. Prevalence of ectoparasitic crustaceans in cetaceans was low: 7.6% in porpoises stranded in the Netherlands (n = 608) and 1.6% in porpoises stranded in Germany (n = 122). All whale lice infections were found on hosts with skin lesions characterised by ulcerations. Morphological investigations revealed characteristic differences between the cyamid species Isocyamus (I.) delphinii and I. deltobranchium identified. Isocyamus deltobranchium was determined in all infected harbour porpoises. I. delphinii was identified on only the pilot whale. Molecular analyses showed 88% similarity of mDNA COI sequences of I. delphinii with I. deltobranchium supporting them as separate species. Phylogenetic analyses of additional gene loci are required to fully assess the diversity and exchange of whale lice species between geographical regions as well as host specificity. Differing whale lice prevalences in porpoises stranded in the Netherlands and Germany could indicate a difference in severity of skin lesions between these areas. It should be further investigated if more inter- or intraspecific contact, e.g., due to a higher density of porpoises or contact with other cetaceans, or a poorer health status of porpoises in the southern North Sea could explain these differences.

Measuring reproducibility of virus metagenomics analyses using bootstrap samples from FASTQ-files

MOTIVATION

High-throughput sequencing data can be affected by different technical errors, e.g. from probe preparation or false base calling. As a consequence, reproducibility of experiments can be weakened. In virus metagenomics, technical errors can result in falsely identified viruses in samples from infected hosts. We present a new resampling approach based on bootstrap sampling of sequencing reads from FASTQ-files in order to generate artificial replicates of sequencing runs which can help to judge the robustness of an analysis. In addition, we evaluate a mixture model on the distribution of read counts per virus to identify potentially false positive findings.

RESULTS

The evaluation of our approach on an artificially generated dataset with known viral sequence content shows in general a high reproducibility of uncovering viruses in sequencing data, i.e. the correlation between original and mean bootstrap read count was highly correlated. However, the bootstrap read counts can also indicate reduced or increased evidence for the presence of a virus in the biological sample. We also found that the mixture-model fits well to the read counts, and furthermore, it provides a higher accuracy on the original or on the bootstrap read counts than on the difference between both. The usefulness of our methods is further demonstrated on two freely available real-world datasets from harbor seals.

AVAILABILITY AND IMPLEMENTATION

We provide a Phyton tool, called RESEQ, available from https://github.com/babaksaremi/RESEQ that allows efficient generation of bootstrap reads from an original FASTQ-file.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

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 seal carcasses potentially subjected to grey seal predation

In order to conduct an objective evaluation of potential ecological effects of grey seal predation on marine mammals, it is essential to establish a broad knowledge base helping in the thorough identification of such cases during post-mortem examination. The aim of this work is to report and discuss outcomes resulting from a retrospective evaluation of harbour (Phoca vitulina) and grey seal (Halichoerus grypus) stranding and necropsy data (n = 3274). In addition, the results are compared to a recent case of definite grey seal predation from Germany as well as reports from other countries. Carcasses potentially subjected to grey seal predation show severe lacerations with a circular pattern leaving a smooth, linear and cut-like wound margin. Large parts of skin and underlying tissue are detached from the body and loss of blubber is common. Occurrence frequencies of encountered lesions are presented and a list of parameters to be used for the assessment of similar cases as well as a complementary decision tree are suggested. With the proposed parameters, categories and tools, a baseline can be built in order to facilitate the standardised recognition of predation cases during post-mortem examinations of seals between groups working with populations across several geographic ranges.

A risk assessment of the effects of mercury on Baltic Sea, Greater North Sea and North Atlantic wildlife, fish and bivalves

A wide range of species, including marine mammals, seabirds, birds of prey, fish and bivalves, were investigated for potential population health risks resulting from contemporary (post 2000) mercury (Hg) exposure, using novel risk thresholds based on literature and de novo contamination data. The main geographic focus is on the Baltic Sea, while data from the same species in adjacent waters, such as the Greater North Sea and North Atlantic, were included for comparative purposes. For marine mammals, 23% of the groups, each composing individuals of a specific sex and maturity from the same species in a specific study region, showed Hg-concentrations within the High Risk Category (HRC) and Severe Risk Category (SRC). The corresponding percentages for seabirds, fish and bivalves were 2.7%, 25% and 8.0%, respectively, although fish and bivalves were not represented in the SRC. Juveniles from all species showed to be at no or low risk. In comparison to the same species in the adjacent waters, i.e. the Greater North Sea and the North Atlantic, the estimated risk for Baltic populations is not considerably higher. These findings suggest that over the past few decades the Baltic Sea has improved considerably with respect to presenting Hg exposure to its local species, while it does still carry a legacy of elevated Hg levels resulting from high neighbouring industrial and agricultural activity and slow water turnover regime.

Handle with Care—Microplastic Particles in Intestine Samples of Seals from German Waters

The Marine Strategy Framework Directive (MSFD) aims to reduce the marine debris burden in the marine environment by 2020. This requires an assessment of the actual situation, which includes the occurrence as well as the caused impacts. Information on both is scarce when it comes to top predators like marine mammals and the burden of microplastic. This is hampered by the limited access to free ranging marine mammals for collecting samples, as well as sample handling. The present study investigated gastrointestinal tracts and faecal samples of harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) regularly occurring in the German North Sea and Baltic Sea with the aim of gaining information on the occurrence of microplastics. In total, 255 particles ≥100 µm (70 fibres, 185 fragments) were found in exemplary ten intestine and nine faecal samples. The findings ranged from zero fibres and six fragments, up to 35 fibres and 55 fragments per sample. Additionally, this study established a protocol for sample handling, microplastic isolation (≥100 µm) and quantification of gastrointestinal tracts and faecal samples of marine mammals with a low share of contamination. This approach helps to quantify the presence of microplastics in free-ranging marine mammals and is therefore applicable to assess the real burden of microplastic presence in the marine environment.

Habitat selection and populations of Corynosoma (Acanthocephala) in the intestines of sea otters (Enhydra lutris) and seals

Acanthocephalans are common intestinal parasites of marine mammals, the most widespread of which is the genus Corynosoma. In this study, parasite infrapopulations of two closely related species of Corynosoma were examined: Corynosoma enhydri from sea otters (Enhydra lutris) in Alaska (n = 12) and California (n = 19), and Corynosoma strumosum from seals in Germany (n = 22). Prevalence of C. enhydri was 100% in Californian otters, with a mean abundance of 30, and 83% in Alaskan otters, with a mean abundance of 232. In seals, C. strumosum had a prevalence of 65%, with a mean abundance of 33. Female C. enhydri dominated both Californian (82%) and Alaskan (79%) infections, while, in seals, female C. strumosum made up 68% of the parasite population. Reproduction rates for C. enhydri, with 16% (California) and 18% (Alaska) of females mated, were low compared to C. strumosum in seals, of which 40% of females were mated. Habitat selection also differed significantly between the two species. Corynosoma enhydri was found most frequently in the second and third fifths of the small intestine, while C. strumosum was found most frequently in the fourth. The differences in habitat selection and prevalence analysed in this study may be related to a trade-off between growth and reproduction between the two species.

Male grey seal commits fatal sexual interaction with adult female harbour seals in the German Wadden Sea

Males of several seal species are known to show aggressive copulating behaviour, which can lead to injuries to or suffocation of females. In the North Sea, grey seal predation on harbour seals including sexual harassment is documented and represents violent interspecific interaction. In this case series, we report pathological and molecular/genetic findings of 11 adult female harbour seals which were found dead in Schleswig–Holstein, Germany, within 41 days. Several organs of all animals showed haemorrhages and high loads of bacteria, indicating their septic spread. All females were pregnant or had recently been pregnant. Abortion was confirmed in three cases. Lacerations were seen in the uterus and vagina in six cases, in which histology of three individuals revealed severe suppurative inflammation with intralesional spermatozoa. Molecular analysis of vaginal swabs and paraffin-embedded samples of the vagina identified grey seal DNA, suggesting violent interspecific sexual interaction with fatal outcome due to septicaemia. This is the first report of female harbour seals dying after coercive copulation by a male grey seal in the Wadden Sea.

Factors associated with keratopathy in captive pinnipeds

OBJECTIVE To identify factors associated with keratopathy in captive pinnipeds and to provide guidance for preventive measures. ANIMALS 319 captive pinnipeds (229 otariids [sea lions and fur seals], 74 phocids [true seals], and 16 odobenids [walrus]) from 25 facilities. PROCEDURES Descriptive data collected from questionnaires completed by facilities and from medical records and physical examinations of pinnipeds were compiled and evaluated. Variables were assessed with χ² tests of homogeneity to determine potential association with keratopathy, and variables with values of P ≤ 0.25 were inserted into the multivariable logistic regression model. RESULTS Results indicated that variables associated with significantly increased odds of keratopathy in captive pinnipeds included lighter or reflective pool color (OR, 2.11; 95% confidence interval [CI], 1.20 to 3.97), pool water salinity < 29 g/L (OR, 3.48; 95% CI, 1.89 to 6.56), and history of eye disease (OR, 3.30; 95% CI, 1.85 to 5.98), trauma (OR, 3.80; 95% CI, 1.72 to 8.89), and having been tested for leptospirosis (OR, 3.83; 95% CI, 1.54 to 10.26). However, odds of keratopathy decreased with UV index ≤ 6 (OR, 0.39; 95% CI, 0.2 to 0.72) and age < 20 years (OR, 0.32; 95% CI, 0.15 to 0.66). CONCLUSIONS AND CLINICAL RELEVANCE Findings indicated that odds of keratopathy in pinnipeds could be reduced by maintenance of pool water salinity ≥ 29 g/L and reduction of UV radiation exposure (eg, with adequate shade structures and use of darker, natural colors). Because UV radiation exposure is cumulative, even small attempts to reduce lifetime exposure to it could help control keratopathy in pinnipeds.

Health effects from contaminant exposure in Baltic Sea birds and marine mammals: A review

Here we review contaminant exposure and related health effects in six selected Baltic key species. Sentinel species included are common eider, white-tailed eagle, harbour porpoise, harbour seal, ringed seal and grey seal. The review represents the first attempt of summarizing available information and baseline data for these biomonitoring key species exposed to industrial hazardous substances focusing on anthropogenic persistent organic pollutants (POPs). There was only limited information available for white-tailed eagles and common eider while extensive information exist on POP exposure and health effects in the four marine mammal species. Here we report organ-tissue endpoints (pathologies) and multiple biomarkers used to evaluate health and exposure of key species to POPs, respectively, over the past several decades during which episodes of significant population declines have been reported. Our review shows that POP exposure affects the reproductive system and survival through immune suppression and endocrine disruption, which have led to population-level effects on seals and white-tailed eagles in the Baltic. It is notable that many legacy contaminants, which have been banned for decades, still appear to affect Baltic wildlife. With respect to common eiders, changes in food composition, quality and contaminant exposure seem to have population effects which need to be investigated further, especially during the incubation period where the birds fast. Since new industrial contaminants continuously leak into the environment, we recommend continued monitoring of them in sentinel species in the Baltic, identifying possible effects linked to climate change, and modelling of population level effects of contaminants and climate change.

Torsion in the Gravid and Nongravid Uterus: A Review of the Literature of an Uncommon Diagnosis

Importance

Uterine torsion is an uncommon but life-threatening clinical situation that requires a high index of suspicion for diagnosis.

Objective

The aim of this study was to review literature and determine the etiology, presentation, diagnosis, and management of uterine torsion in the gravid and nongravid patients.

Evidence Acquisition

A literature search was undertaken by our research librarian using the search engines PubMed and CINAHL. The search terms used were "uterine torsion" OR (uterus and torsion). The search was limited to the English language, but the years searched were unlimited.

Results

The search identified 177 articles, 91 of which are the basis for this review. There have been 41 cases or gravid uterine torsion, their characteristics, and symptoms published since 2006. Torsion is rare in nongravid patients, but can still occur.

Conclusion and Relevance

Uterine torsion is rare, can affect all ages, and can have significant implications for women. Prompt recognition allows for timely intervention and can mitigate harm.

A review of pathogens in selected Baltic Sea indicator species

Here we review the state-of-the-art of pathogens in select marine and terrestrial key species of the Baltic Sea, i.e. ringed seal (Pusa hispida), harbour seal (Phoca vitulina), grey seal (Halichoerus grypus), harbour porpoise (Phocoena phocoena), common eider (Somateria mollissima), pink-footed goose (Anser brachyrhynchus) and white-tailed eagle (Haliaeetus albicilla). This review is the first to merge and present available information and baseline data for the FP7 BONUS BaltHealth project: Baltic Sea multilevel health impacts on key species of anthropogenic hazardous substances. Understanding the spread, prevalence and effects of wildlife pathogens is important for the understanding of animal and ecosystem health, ecosystem function and services, as well as human exposure to zoonotic diseases. This review summarises the occurrence of parasites, viruses and bacteria over the past six decades, including severe outbreaks of Phocine Distemper Virus (PDV), the seroprevalence of Influenza A and the recent increase in seal parasites. We show that Baltic high trophic key species are exposed to multiple bacterial, viral and parasitic diseases. Parasites, such as C. semerme and P. truncatum present in the colon and liver Baltic grey seals, respectively, and anisakid nematodes require particular monitoring due to their effects on animal health. In addition, distribution of existing viral and bacterial pathogens, along with the emergence and spread of new pathogens, need to be monitored in order to assess the health status of key Baltic species. Relevant bacteria are Streptococcus spp., Brucella spp., Erysipelothrix rhusiopathiae, Mycoplasma spp. and Leptospira interrogans; relevant viruses are influenza virus, distemper virus, pox virus and herpes virus. This is of special importance as some of the occurring pathogens are zoonotic and thus also pose a potential risk for human health. Marine mammal handlers, as well as civilians that by chance encounter marine mammals, need to be aware of this risk. It is therefore important to continue the monitoring of diseases affecting key Baltic species in order to assess their relationship to population dynamics and their potential threat to humans. These infectious agents are valuable indicators of host ecology and can act as bioindicators of distribution, migration, diet and behaviour of marine mammals and birds, as well as of climate change and changes in food web dynamics. In addition, infectious diseases are linked to pollutant exposure, overexploitation, immune suppression and subsequent inflammatory disease. Ultimately, these diseases affect the health of the entire ecosystem and, consequently, ecosystem function and services. As global warming is continuously increasing, the impact of global change on infectious disease patterns is important to monitor in Baltic key species in the future.

Intestinal displacements in older harbour and grey seals

Intestinal displacements including volvulus, torsion and invagination have been reported in various terrestrial and marine mammals. We conducted pathological investigations on 157 seals that had either stranded on the coasts of the North or Baltic Sea between 1996 and 2015 (115 harbour seals, >19 mo old; 21 grey seals, >13 mo old) or died while in human care (18 harbour seals, >19 mo old; 3 grey seals, >13 mo old). Intestinal displacements were found in 23% of the examined free-living harbour seals, in 5% of the stranded grey seals and in 17% of the harbour seals in human care. Intestinal volvulus, found in 24 cases, was characterized by twisting of the intestine along the mesenteric axis (180-540°) resulting in vascular obstruction and haemorrhagic infarction. In harbour seals, the sex ratio of individuals suffering from volvulus tended to be biased towards females during April to June, suggesting an elevated risk for pregnant females around birth time. Invagination was detected in 11 cases, 5 of which suffered from additional volvulus. Pathological findings associated with intestinal volvulus and invagination were sero-haemorrhagic effusions in the abdominal cavity. Enteritis, parasitic infection with gastric nematodes and intestinal acanthocephalans and bacterial infection with predominantly Clostridium perfringens and Escherichia coli were observed in most of the affected animals. In total, 30 investigated harbour and grey seals suffered from intestinal displacements. Pregnant females seemed to be more vulnerable around birth time. Causes of intestinal displacements remain undetermined, but are likely multifactorial.

Pathological findings in North Sea and Baltic grey seal and harbour seal intestines associated with acanthocephalan infections

Grey seals Halichoerus grypus and harbour seals Phoca vitulina are common seal species in the North and Baltic seas and final hosts of Corynosoma acanthocephalans. C. strumosum and C. magdaleni infect the small intestines of both seal species. In contrast to harbour seals, Baltic grey seals in the past have regularly displayed severe C. semerme infections in the caecum and colon, with associated tunica muscularis hypertrophy, inflammation and ulcerations as part of the Baltic seal disease complex (BSDC). Pathogenesis and correlation of acanthocephalan infections with these lesions are still unknown. This study describes the intestinal pathology and parasitic distribution in each seal species. Grey seal (n = 83) and harbour seal (n = 1156) intestines of all age groups and sexes, collected in Poland, Germany and Estonia from 1998 to 2017, were investigated. Most harbour seals came from the North Sea, whereas grey seals were predominantly derived from the Baltic Sea. Both species featured mild to moderate small intestinal infections. Grey seals showed colonic infections not found in harbour seals and featured a chronic erosive to ulcerative, eosinophilic or lympho-plasmacytic colitis with tunica muscularis hypertrophy, indicating still prevailing clinical signs of the BSDC. Harbour seals displayed granulomatous, eosinophilic, lympho-plasmacytic or catarrhal enteritis. The prevalence of acanthocephalan infections in harbour seals increased from 2012 onwards. Furthermore, significant associations between acanthocephalan infection and the presence of intestinal inflammation were found for both seal species. This study suggests that the level of acanthocephalan infection and associated lesions are suitable seal population health indicators, with the colon being a specific target organ for Baltic grey seal health monitoring.

NEW APPROACH TO STRESS RESEARCH IN PHOCIDS-POTENTIAL OF DEHYDROEPIANDROSTERONE AND CORTISOL/DEHYDROEPIANDROSTERONE RATIO AS MARKERS FOR STRESS IN HARBOR SEALS ( PHOCA VITULINA) AND GRAY SEALS ( HALICHOERUS GRYPUS)

Cortisol is known to reflect the level of the stress response. However, measuring the cortisol concentration only once fails to provide sufficient information about the duration of the stress exposure. Moreover, handling is an acute stressor and increases cortisol secretion especially in wildlife species. Yet, in phocids reliable indicators are missing that reflect potential chronic effects of stress. The adrenal-derived steroid hormone dehydroepiandrosterone (DHEA) has been described as biomarker for the assessment of the stress status but has not been applied to marine mammal stress research. Therefore, DHEA, the sulfated precursor DHEAS and the cortisol/DHEA ratio were determined in serum of different seals. One group consisted of harbor ( Phoca vitulina) and gray seals ( Halichoerus grypus) that were habituated to human handling. The other two groups included healthy and free-ranging seals suffering from a disease. Blood samples were taken from 11 habituated (six males, five females), 17 wild_healthy (13 males, four females), and nine wild_diseased seals (four males, five females). No differences in serum cortisol levels could be detected between wild_healthy and wild_diseased seals. On the contrary, wild_diseased seals showed the lowest DHEA concentration compared to the other two groups. Wild_diseased seals also revealed the highest cortisol/DHEA ratio compared to the habituated_zoo (2,074.7 ± 351.4 vs. 121.5 ± 26.8, P < 0.001) and wild_healthy seals (827.9 ± 214.3, P < 0.01). DHEA and the cortisol/DHEA ratio may reflect differences in the functionality of the hypothalamic-pituitary-adrenal axis and therefore represent valuable tools for the assessment of stress-related effects in seals.

Fatal pulmonary parafilaroidiasis in a free-ranging subantarctic fur seal (Arctocephalus tropicalis) coinfected with two gammaherpesviruses and Sarcocystis sp

A juvenile subantarctic fur seal (Arctocephalus tropicalis) found dead in Santa Catarina state, southern Brazil, presented with disseminated verminous pneumonia due to Parafilaroides sp. A concomitant infection with two different gammaherpesviruses was identified by PCR in different tissues; one of them possibly a novel species (tentatively named Otariid herpesvirus 7). Sarcocystis sp. DNA was identified molecularly in skeletal muscle samples with intrasarcoplasmic bradyzoites and no apparent tissue response. All analyzed samples (mandibular, laryngeal, tracheal, and mesenteric lymph nodes, and lung) were PCR-negative for Brucella spp. The most likely cause of death was severe pulmonary parafilaroidiasis. The pathogenic role of the gammaherpesviruses in several of the tissues was not evident. This study describes the pathogenicity of Parafilaroides sp. in a subantarctic fur seal, widens the host range of herpesvirus in pinnipeds, and reports the first molecular identification of Sarcocystis sp. in this species.

There and back again - The return of the nasal mite Halarachne halichoeri to seals in German waters

The nasal mite Halarachne halichoeri (Acari; Halarachnidae) is adapted to live in the marine environment with pinnipeds as its primary host and can cause different levels of upper respiratory disease in both harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus). Historical reports of H. halichoeri occurring in seals from German waters date back to the end of the 19th century. However, with the disappearance of the grey seal from German waters as a consequence of human over-exploitation, the mite vanished from the records and the fauna found in Germany for more than a century. Although a stranding network has been monitoring marine mammal health along the German coasts since the mid 1980s with extensive post-mortem investigations, this study reports the first and subsequent findings of H. halichoeri in grey and harbour seals from the North and Baltic Sea from 2014 onwards. The re-emergence of this endoparasitic mite in North and Baltic Sea habitats seems to have occurred simultaneously with the recolonisation of its primary host, the grey seal. During the course of its recolonisation, it was probably transmitted to harbour seals sharing the same haul-out sites. Molecular analyses showed a high similarity of rDNA sequences with H. halichoeri collected from sea otters (Enhydra lutris) in the USA. However, more thorough analyses of additional gene loci are required to fully assess the exchange and diversity of this parasite between geographically isolated regions and species.

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First finding of endoparasitic seal mite H. halichoeri in Germany after >100 years.

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Recolonisation of North and Baltic Sea in unison with primary host grey seal.

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Morphological comparison with century-old museum specimens.

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Minor histopathological alterations in upper respiratory tract associated.

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High genetic similarity of ITS-2 with H. halichoeri from sea otters in the USA.

IDIOPATHIC IRON OVERLOAD IN A HARBOR SEAL ( PHOCA VITULINA)

Iron overload has been described in various wild species. The majority of cases involve captive animals, often associated with increased dietary iron uptake. Here a case of idiopathic iron overload in a female adult harbor seal under human care is presented. The animal displayed a progressive anorexia, apathy, and increased serum iron levels. Radiographs showed radiopaque foreign bodies in the stomach. The seal died during an elective laparotomy. Twenty-five coins and two metal rings were removed from the stomach. Histopathologic examination revealed iron storage without cellular damage in liver, spleen, kidney, and pulmonary and mesenteric lymph nodes. Atomic absorption spectrophotometry analysis for iron revealed values thirty times above the reference ranges in spleen and liver; however, the coins only contain minor levels (parts per million) of iron. The etiology of the iron overload in this animal remains unclear. A multifactorial process cannot be excluded.

Osteoarthritis of the temporomandibular joint in the Eastern Atlantic harbour seal (Phoca vitulina vitulina) from the German North Sea: a study of the lesions seen in dry bone

BACKGROUND

Pathological changes and resulting functional impairment of the temporomandibular joint (TMJ) can substantially affect physical condition, morbidity, and mortality of wildlife species. Analysis of TMJ disorders is therefore of interest for the characterization of the health status of populations of wild mammals. This paper, for the first time, analyses the prevalence of TMJ osteoarthritis (TMJ-OA) and the spectrum of osteoarthritic bone lesions of the TMJ in the Eastern Atlantic harbour seal (Phoca vitulina vitulina), applying a standardized scoring system. Dry skulls of 1872 individuals from the German North Sea, collected between 1961 and 1994, were examined for lesions consistent with a diagnosis of TMJ-OA. Of the skulls, 913 (48.8%) were from male, 959 (51.2%) from female seals, with age at death ranging from 2 weeks to 25 years. Possible associations of TMJ-OA with dental or periodontal disorders were also analysed.

RESULTS

Lesions consistent with TMJ-OA were found in 963 (53.9%) of the 1787 juvenile/subadult (5 weeks to 5 years of age) and adult (> 5 years) specimens, the condition mostly (95.0% of affected individuals) occurring in a bilateral fashion. Males were affected more frequently than females (p < 0.001), while lesion severity tended to be higher in females (p < 0.05). Severity of TMJ-OA lesions was positively correlated with age (p < 0.001). Lesion severity was also weakly positively correlated with the number of fractured teeth (p < 0.05) and of intravitally lost teeth (p < 0.01), when controlling for age at death as a confounder.

CONCLUSIONS

TMJ-OA is a common disorder in the Eastern Atlantic harbour seal. The more pronounced severity of the lesions in females compared to males is basically attributed to the higher average age of the female subsample. The causes underlying the high prevalence of TMJ-OA in the studied assemblage remain unknown. Most of the specimens (75.3%) analysed in the present study were found dead during the first phocine distemper virus epizootic in 1988. Therefore, it is assumed that, contrary to other museum collections, only little overrepresentation of pathological skeletal conditions is present in this death sample compared with the population from which it originated.

BRUCELLA PINNIPEDIALIS IN GREY SEALS ( HALICHOERUS GRYPUS) AND HARBOR SEALS ( PHOCA VITULINA) IN THE NETHERLANDS

Brucellosis is a zoonotic disease with terrestrial or marine wildlife animals as potential reservoirs for the disease in livestock and human populations. The primary aim of this study was to assess the presence of Brucella pinnipedialis in marine mammals living along the Dutch coast and to observe a possible correlation between the presence of B. pinnipedialis and accompanying pathology found in infected animals. The overall prevalence of Brucella spp. antibodies in sera from healthy wild grey seals ( Halichoerus grypus; n=11) and harbor seals ( Phoca vitulina; n=40), collected between 2007 and 2013 ranged from 25% to 43%. Additionally, tissue samples of harbor seals collected along the Dutch shores between 2009 and 2012, were tested for the presence of Brucella spp. In total, 77% (30/39) seals were found to be positive for Brucella by IS 711 real-time PCR in one or more tissue samples, including pulmonary nematodes. Viable Brucella was cultured from 40% (12/30) real-time PCR-positive seals, and was isolated from liver, lung, pulmonary lymph node, pulmonary nematode, or spleen, but not from any PCR-negative seals. Tissue samples from lung and pulmonary lymph nodes were the main source of viable Brucella bacteria. All isolates were typed as B. pinnipedialis by multiple-locus variable number of tandem repeats analysis-16 clustering and matrix-assisted laser desorption ionization-time of flight mass spectrometry, and of sequence type ST25 by multilocus sequence typing analysis. No correlation was observed between Brucella infection and pathology. This report displays the isolation and identification of B. pinnipedialis in marine mammals in the Dutch part of the Atlantic Ocean.

First record of Halocercus sp. (Pseudaliidae) lungworm infections in two stranded neonatal orcas (Orcinus orca)

Orca (Orcinus orca) strandings are rare and post-mortem examinations on fresh individuals are scarce. Thus, little is known about their parasitological fauna, prevalence of infections, associated pathology and the impact on their health. During post-mortem examinations of two male neonatal orcas stranded in Germany and Norway, lungworm infections were found within the bronchi of both individuals. The nematodes were identified as Halocercus sp. (Pseudaliidae), which have been described in the respiratory tract of multiple odontocete species, but not yet in orcas. The life cycle and transmission pathways of some pseudaliid nematodes are incompletely understood. Lungworm infections in neonatal cetaceans are an unusual finding and thus seem to be an indicator for direct mother-to-calf transmission (transplacental or transmammary) of Halocercus sp. nematodes in orcas.

Prevalence and molecular characterisation of Acanthocephala in pinnipedia of the North and Baltic Seas

Harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) are final hosts of acanthocephalans in the German North and Baltic Seas. Parasitic infections in seals can cause pathological changes, which may result in deteriorated health of the host. Common gastrointestinal parasites of harbour and grey seals are acanthocephalans and a number of 275 of 2460 (11.2%) investigated seals from 1996 to 2013 were infected with Corynosoma spp. (Acanthocephala, Polymorphidae). The prevalence showed a wave-like pattern: it increased from 1.2% and 0.4% in 1996 and 1997, respectively, to 23.9% during the second phocine distemper epizootic in 2002 and decreased to 6.2% in 2004. In 2005, prevalence peaked again with 25.0% followed by a decrease to 9.3% in 2009 and an increase to 38.5% in 2012. Statistical analysis revealed that harbour seals originating from the North Sea showed a higher prevalence than grey seals, whereas no significant difference between grey and harbour seals from the Baltic Sea was observed. Furthermore, juvenile pinnipedia from the North Sea were significantly less infected with Corynosoma spp. than seals older than seven month. Molecular species identification as well as phylogenetic relationship analysis among the detected Corynosoma species were achieved by sequencing and comparisons of the ribosomal ITS1-5.8S-ITS2-complex and cytochrome-c-oxidase I gene. Molecular analysis resulted in a newly arranged distribution of Acanthocephala in the North Sea as in contrast to previous studies, C. strumosum could not be confirmed as predominant species. Instead, C. magdaleni and a C. magdaleni isolate (isolate Pv1NS) with an atypical number of longitudinal rows of hooks at the proboscis were detected. Furthermore, morphological and molecular analyses indicate the possible finding of a cryptic species (Candidatus Corynosoma nortmeri sp. nov.).

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The prevalence of acanthocephalans in pinnipedia fluctuated between 1996 and 2013.

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Molecular analysis reveals new distribution of Acanthocephala in the North Sea.

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Proposed new species named Corynosoma nortmeri sp. nov.

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Use of molecular markers is crucial for a reliable species discrimination.

Pinnipediae

This chapter reviews common diseases of pinnipeds, including species in the Otariidae (fur seals and sea lions), Phocidae (true seals), and Odobenidae (walrus) families. Much of the knowledge on pathologic conditions of pinnipeds comes from necropsies of stranded animals and those housed in captivity. As such, disease knowledge is biased toward species frequently housed in zoos and aquaria, those that strand more commonly, or those in which free-ranging populations are more easily accessible. Though historically systematic evaluations of wild populations have rarely been accomplished, in the past 10 years, with advances in marine mammal medicine and anesthesia, biologists and veterinarians more frequently completed live animal health field investigations to evaluate health and disease in free-ranging pinniped populations.

Surgical repair of a tibial fracture in a two-week-old grey seal (Halichoerus grypus)

Objective: To report the successful management of a suspected infected tibial fracture in a common grey seal.

Study design: Case report.

Animal: Female common grey seal (Halichoerus grypus), 2 weeks old, 20 kg.

Methods: A closed, complete, transverse fracture of the left tibial distal diaphysis was debrided, reduced and stabilized using a string-of-pearls (SOP) locking plate covered with polymethylmethacrylate impregnated with gentamicin. Fracture of the ipsilateral fibula was left untreated. Postoperative radiographs were obtained immediately, and at 10 days, three weeks, and six weeks post-surgery, and a computed tomographic examination was performed 2.5 months post-surgery. A species-specific progressive rehabilitation programme was conducted.

Results: Bone healing of both fractures and absence of injury of the distal tibial growth plate were evident on the 2.5 month follow-up examination, and also full range-of-motion of the flipper was preserved and no lameness or difficulty with swimming and hunting were detected. On computed tomography, signs of chronic left coxofemoral and ilial wing trauma were incidentally detected. The seal was released three months postoperatively.

Conclusion: A transverse infected distal fracture of the tibia and fibula in a young common grey seal was successfully managed with the combination of single SOP plating of the tibia, local antibiotic release and a specific rehabilitation programme.

Clinical relevance: Surgical treatment of a long-bone fracture in a wild immature grey seal was successful with a combination of techniques adapted to the species.

Marine debris in harbour porpoises and seals from German waters

Records of marine debris in and attached to stranded harbour porpoises (Phocoena phocoena), harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) were studied comprising information on 6587 carcasses collected along the German coast between 1990 and 2014, the decomposition state allowed for necropsy in 1622 cases. Marine debris items were recorded in 31 carcasses including 14 entanglements (5 harbour porpoises, 6 harbour seals, 3 grey seals) and 17 cases of ingestion (4 harbour porpoises, 10 harbour seals, 3 grey seals). Objects comprised general debris (35.1%) and fishing related debris (64.9%). Injuries associated with marine debris included lesions, suppurative ulcerative dermatitis, perforation of the digestive tract, abscessation, suppurative peritonitis and septicaemia. This study is the first investigation of marine debris findings in all three marine mammal species from German waters. It demonstrates the health impacts marine debris can have, including severe suffering and death. The results provide needed information on debris burdens in the North and Baltic Seas for implementing management directives, such as the Marine Strategy Framework Directive (MSFD).

Identification of a novel host-specific IgG protease in Streptococcus phocae subsp. phocae

Streptococcus (S.) phocae subsp. phocae causes bronchopneumonia and septicemia in a variety of marine mammals. Especially in harbor seals infected with phocine distemper virus it plays an important role as an opportunistic pathogen. This study was initiated by the detection of IgG cleavage products in Western blot analysis after incubation of bacterial supernatant with harbor seal serum. Hence, the objectives of this study were the identification and characterization of a secreted IgG cleaving protease in S. phocae subsp. phocae isolated from marine mammals. To further identify the responsible factor of IgG cleavage a protease inhibitor profile was generated. Inhibition of the IgG cleaving activity by iodoacetamide and Z-LVG-CHN₂ indicated that a cysteine protease is involved. Moreover, an anti-IdeS antibody directed against the IgG endopeptidase IdeS of S. pyogenes showed cross reactivity with the putative IgG protease of S. phocae subsp. phocae. The IgG cleaving factor of S. phocae subsp. phocae was identified through an inverse PCR approach and designated IdeP (Immunoglobulin G degrading enzyme of S. phocae subsp. phocae) in analogy to the cysteine protease IdeS. Notably, recombinant (r) IdeP is a host and substrate specific protease as it cleaves IgG from grey and harbor seals but not IgG from harbor porpoises or non-marine mammals. The identification of IdeP represents the first description of a protein in S. phocae subsp. phocae involved in immune evasion. Furthermore, the fact that IdeP cleaves solely IgG of certain marine mammals reflects functional adaption of S. phocae subsp. phocae to grey and harbor seals as its main hosts.

Influenza A (H10N7) Virus Causes Respiratory Tract Disease in Harbor Seals and Ferrets

Avian influenza viruses sporadically cross the species barrier to mammals, including humans, in which they may cause epidemic disease. Recently such an epidemic occurred due to the emergence of avian influenza virus of the subtype H10N7 (Seal/H10N7) in harbor seals (Phoca vitulina). This epidemic caused high mortality in seals along the north-west coast of Europe and represented a potential risk for human health. To characterize the spectrum of lesions and to identify the target cells and viral distribution, findings in 16 harbor seals spontaneously infected with Seal/H10N7 are described. The seals had respiratory tract inflammation extending from the nasal cavity to bronchi associated with intralesional virus antigen in respiratory epithelial cells. Virus infection was restricted to the respiratory tract. The fatal outcome of the viral infection in seals was most likely caused by secondary bacterial infections. To investigate the pathogenic potential of H10N7 infection for humans, we inoculated the seal virus intratracheally into six ferrets and performed pathological and virological analyses at 3 and 7 days post inoculation. These experimentally inoculated ferrets displayed mild clinical signs, virus excretion from the pharynx and respiratory tract inflammation extending from bronchi to alveoli that was associated with virus antigen expression exclusively in the respiratory epithelium. Virus was isolated only from the respiratory tract. In conclusion, Seal/H10N7 infection in naturally infected harbor seals and experimentally infected ferrets shows that respiratory epithelial cells are the permissive cells for viral replication. Fatal outcome in seals was caused by secondary bacterial pneumonia similar to that in fatal human cases during influenza pandemics. Productive infection of ferrets indicates that seal/H10N7 may possess a zoonotic potential. This outbreak of LPAI from wild birds to seals demonstrates the risk of such occasions for mammals and thus humans.

Seasonal Variation of Harbor Seal's Diet from the Wadden Sea in Relation to Prey Availability

The Wadden Sea has an important role for marine mammals in terms of resting, nursing and foraging. Harbor seal is the most abundant marine mammal species in this area. The use of the food resources of the Wadden Sea by seals is not clear, and previous studies showed that this species can travel kilometers away from their haul-outs to forage in the North Sea. In this study, we analyzed the stable isotopes of vibrissae from 23 dead harbor seals found on the island of Sylt to investigate their diet. The predator´s carbon and nitrogen isotope compositions were compared to the compositions of different potential prey items from the Sylt-Rømø Bight and from the North Sea in order to study seasonal pattern in the diet and in the foraging location. In parallel, seasonal variation of abundance and biomass of the potential prey items from the Sylt-Rømø Bight were studied and compare to their contribution to the seal´s diet. The results revealed a change in the seal´s diet from pelagic sources in spring to a benthic based diet in summer, and an increasing use of the North Sea resources in fall and winter in accordance with the seasonal variation of the availability of prey in the Sylt-Rømø Bight.