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Pseudaliid lungworm (Metastrongyloidea) infections and associated secondary bacterial infections may severely affect the health status of harbour porpoises (Phocoena phocoena) in German waters. The presented retrospective analysis including data from 259 harbour porpoises stranded between 2006 and 2018 on the German federal state of Schleswig-Holstein's North Sea coast showed that 118 (46%) of these stranded individuals harboured a lungworm infection. During this 13-year period, a significant difference in annual lungworm prevalence was only observed between the years 2006 and 2016. Lungworm coinfections of bronchi and pulmonary blood vessels were observed in 85.6% of positive cases. Mild infection levels were detected in 22.9% of infected animals and were most common in the age class of immature individuals (74.1%). Moderate and severe infections were present in 38.1% and 39.0% of the lungworm positive animals, respectively. Their distribution in immatures (51.1% and 54.3%) and adults (48.9% and 43.4%) did not show significant differences. In stranded animals, lungworm diagnosis can be easily obtained via necropsy, while reliable lungworm diagnosis in living porpoises requires invasive bronchoscopy or faecal examination, which is difficult to obtain in cetaceans. To overcome this issue, an enzyme-linked immunosorbent assay (ELISA) and immunoblot based on recombinant major sperm protein (MSP) of the cattle lungworm were evaluated as potential diagnostic tools in harbour porpoises. However, in contrast to hitherto other investigated host species, no reliable antibody response pattern was detectable in harbour porpoise serum/plasma or whole blood samples. Thus, MSP-based serological tests are considered unsuitable for lungworm diagnosis in harbour porpoises., Graphical abstract Image 1, Highlights • Overall lungworm prevalence in North Sea harbour porpoises was 46%. • Co-infection of bronchial tree and pulmonary vessels in 85.5% of positive animals. • Most harbour porpoises suffered from moderate (38%) or severe infection (39%). • Both MSP-ELISA and immunoblot did not reveal reliable results.

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 info:eu-repo/semantics/publishedVersion

142 pages, The Working Group on Marine Mammal Ecology (WGMME), chaired by Anita Gilles (Germany) and Anders Galatius (Denmark), met at the Institute for Terrestrial and Aquatic Wildlife Re-search, University of Veterinary Medicine Hannover, Foundation, in Büsum, Germany, during 11–14 February 2019. On behalf of the working group, the chairs would like to thank the Institute for Terrestrial and Aquatic Wildlife Research (ITAW) for hosting the meeting. A total of 17 participants from eight countries attended the meeting on site. The list of partici-pants, including those contributing remotely, and contact details are given in Annex 1. The Chairs acknowledge the diligence and hard work of all the participants before, during and after the meeting, which ensured that the Terms of Reference could all be addressed. The Working Group gratefully acknowledges the support given by several additional experts that kindly pro-vided information and/or reports for use by WGMME and evaluated the threats matrices and related text (see Annex 1). Two terms of references were standing ToRs; under the first of these, ToR A, new and updated information on seal and cetacean population abundance, population/stock structure, manage-ment frameworks, and anthropogenic threats to individual health and population status were reviewed. Usually data on marine mammal surveys are only conducted during one season, but new data from Ireland revealed profound differences between summer and winter abundance and distribution of cetaceans, with implications for the spatial management of these species. New habitat modelling for cetacean species in the Northwest European Seas and North Atlantic Ocean and Mediterranean based on collated survey data as well as findings on threats to marine mammals such as bycatch, pollution, marine debris and noise were summarised under this ToR. Under ToR B, WGMME reviewed information on the ecological roles of marine mammals, ex-panding on efforts to review impacts on fisheries, interspecific competition, diet and impact on fish stocks from previous reports. The complexity and multitude of ecological interactions is un-derlined. A special emphasis under this ToR was put on the role of marine mammals as hosts and vectors of parasites., ToR C was implemented to review aspects of marine mammal fishery interactions not covered by ICES WGBYC. In 2019, WGMME focused its efforts on i) reviewing seal interactions with fisheries, including the numbers of bycaught seals, ii) investigating additional data sources for cetacean bycatch such as strandings, voluntary recording schemes and interview surveys, iii) identifying of potential bycatch risk areas, and iv) a review of recent work on setting safe limit thresholds for bycatch of marine mammals. To implement bycatch data in the management of marine mammals it is stressed that they should be aggregated on a management unit basis and corresponding data on abundance should be available. Under ToR D, WGMME followed up and updated on the 2015 threat matrix for the main marine mammal species in each of the regional sea areas. In addition to this update, a review of cumu-lative impacts from multiple environmental pressures and recent efforts to meaningfully analyse such cumulative impacts was produced. The approaches used to assess cumulative impacts are usually limited to a particular pressure. Efforts to expand the scopes of these tools are impeded by the complexity of the relevant interactions and knowledge gaps. ToR E, updating the database for seals, is the second standing term of reference. This year, WGMME adapted the ICES WGMME seal database to a proper database format and updated the data. WGMME also repeated its support for a data call from OSPAR to provide data for assessments under OSPAR indicators M3 and M5 on seal abundance and distribution, The WGMME updated ToRs for 2020 (see Annex 2) and discussed meeting venues. The Institute of Marine Sciences (ICM-CSIC) offered to host the 2020 meeting in Barcelona (Spain) alongside the meeting of ICES WGBIODIV in order to arrange common sessions and establish cooperation between the two groups (see proposed ToR B for 2020)

Harbour porpoises (Phocoena phocoena) are the only native cetacean species in the German North and Baltic Seas and the final host of Anisakis (A.) simplex, which infects their first and second gastric compartments and may cause chronic ulcerative gastritis. Anisakis simplex belongs to the family Anisakidae (Ascaridoidea, Rhabditida) as well as the phocine gastric nematode species Pseudoterranova (P.) decipiens and Contracaecum (C.) osculatum. These nematode species are the main causative agents for the zoonosis anisakidosis. The taxonomy of these genus with life cycles including crustaceans and commercially important fish is complex because of the formation of sibling species. Little is known about anisakid species infecting porpoises in the study area. Mature nematodes and larval stages are often identifiable only by molecular methods due to high morphological and genetic similarity. The restriction fragment length polymorphism (RFLP) method is an alternative to sequencing and was applied to identify anisakid nematodes found in harbour porpoises from the North Sea, Baltic Sea and North Atlantic to species level for the first time. In the study areas, five gastric nematodes from different harbour porpoise hosts were selected to be investigated with restriction enzymes HinfI, RsaI and HaeIII, which were able to differentiate several anisakid nematode species by characteristic banding patterns. Anisakis simplex s. s. was the dominant species found in the North Sea and Baltic porpoises, identified by all three restriction enzymes. Additionally, a hybrid of A. simplex s. s. and A. pegreffii was determined by HinfI in the North Sea samples. Within the North Atlantic specimens, A. simplex s. s., P. decipiens s. s. and Hysterothylacium (H.) aduncum were identified by all enzymes. This demonstrates the value of the RFLP method and the chosen restriction enzymes for the species identification of a broad variety of anisakid nematodes affecting the health of marine mammals.

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), estrogen 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.

In the North Sea, white-beaked dolphins (Lagenorhynchus albirostris) occur regularly and are the second most common cetacean in the area, while their close relative, the Atlantic white-sided dolphin (Lagenorhynchus acutus), prefers the deeper waters of the northern North Sea and adjacent Atlantic Ocean. Though strandings of both species have occurred regularly in the past three decades, they have decreased in the southern North Sea during the last years. Studies describing necropsy findings in stranded Lagenorhynchus spp. are, to date, still scarce, while information gained through post-mortem examinations may reveal valuable information about underlying causes of this decline, including age structure and the reproduction status. Therefore, we retrospectively assessed and compared the necropsy results from fresh Lagenorhynchus spp. stranded along the southeastern North Sea between 1990 and 2019. A full necropsy was performed on 24 white-beaked dolphins and three Atlantic white-sided dolphins from the German and Dutch coast. Samples of selected organs were taken for histopathological, bacteriological, mycological, parasitological and virological examinations. The most common post-mortem findings were emaciation, gastritis and pneumonia. Gastritis and ulceration of the stomach was often associated with an anisakid nematode infection. Pneumonia was most likely caused by bacterial infections. Encephalitis was observed in three animals and morbillivirus antigen was detected immunohistochemically in one case. Although the animal also showed pneumonic lesions, virus antigen was only found in the brain. Parasitic infections mainly affected the gastro-intestinal tract. Lungworm infections were only detected in two cases and no associations with pathological alterations were observed. Stenurus spp. were identified in two of three cases of parasitic infections of the ears. Twelve of the 26 white-beaked dolphins stranded in Germany were found between 1993 and 1994, but there was no evidence of epizootic disease events or mass strandings during the monitored period.

Between the 8 th January and the 25 th February 2016, the largest sperm whale Physeter macrocephalus mortality event ever recorded in the North Sea occurred with 30 sperm whales stranding in five countries within six weeks. All sperm whales were immature males. Groups were stratified by size, with the smaller animals stranding in the Netherlands, and the largest in England. The majority (n = 27) of the stranded animals were necropsied and/ or sampled, allowing for an international and comprehensive investigation into this mortality event. The animals were in fair to good nutritional condition and, aside from the pathologies caused by stranding, did not exhibit significant evidence of disease or trauma. Infectious agents were found, including various parasite species, several bacterial and fungal pathogens and a novel alphaherpesvirus. In nine of the sperm whales a variety of marine litter was found. However, none of these findings were considered to have been the primary cause of the stranding event. Potential anthropogenic and environmental factors that may have caused the sperm whales to enter the North Sea were assessed. Once sperm whales enter the North Sea and head south, the water becomes progressively shallower (

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.

Peribullar sinuses of harbour porpoises Phocoena phocoena are parasitized with high prevalence by the nematode Stenurus minor. The effect of S. minor on the hearing ability of this species is still undetermined. Here, we review the occurrence of S. minor in the inner ear of harbour porpoises recovered from strandings in the North and Baltic Seas. In particular, we present the results from ears collected in German and Danish waters from 2002 to 2016 and from Dutch waters from 2010 to 2016. While the prevalence of S. minor in pterygoid and peribullar sinuses and tympanic cavity was high in harbour porpoises (66.67% in our cases), its prevalence in the cochlea was rare. Only 1 case out of 129 analysed by either histology, electron microscopy or immunofluorescence showed the presence of a nematode parasite morphologically consistent with S. minor at the most basal portion of the right cochlea. This individual also had severe haemorrhage along the right cochlear spiral, which was likely caused by ectopic S. minor migration. Although this animal might have had impaired hearing in the right ear, it was otherwise in good body condition with evidence of recent feeding. These findings highlight the need to study the effect of parasites on hearing, and other pathological changes that might impair appropriate processing of acoustic information.

SUMMARY Parasitism is ubiquitous in wildlife, but little is known about the dynamics of parasitic infections and associated diseases in marine mammals. This thesis aimed to characterise the parasite fauna of harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) to assess the impact on their health status and to improve the knowledge about the life history of their lungworm species. Parasitological investigations were carried out on harbour porpoises originating from the German North and Baltic Seas and the Norwegian North Sea. The parasites found in porpoises originated mainly from the respiratory tract and comprised four pseudaliid nematodes (Pseudalius inflexus, Torynurus convolutus, Halocercus invaginatus, Stenurus minor), one ascaridoid nematode (Anisakis simplex) and two trematodes (Campula oblonga, Pholeter gastrophilus). The finding of H. invaginatus was the first geographic record from German waters. Differences were found in the severity of the parasitic infection between stranded and bycaught animals as well as between porpoises from different areas. A correlation was shown between parasitic infection and observed lesions. Lungworm prevalence and intensity of infections increased with age suggesting horizontal transmission through the food web. The data also indicated that infections were accumulated with age and long‐lived. The occurrence of whale‐lice, Isocyamus delphinii (Crustacea: Amphipoda: Cyamidae), infestation was described in a stranded harbour porpoise. The emaciated animal had multiple, partially scarred wounds to which numerous small crustaceans were attached. The whale‐lice showed a significant sexual dimorphism and their population was male biased. The lesions in the lung were found to be the likely cause of death in this porpoise, and the ectoparasites were not diagnosed to be a major health threat to the animal. The skin wounds’ origin remained unclear, but the lice seemed to be closely associated and dependent on the wounds of this host. In this first and unusual occurrence of I. delphinii on a harbour porpoise from German waters, the transmission was probably interspecific and skin wounds were likely the necessary means for the parasites to attach and remain on a porpoise. Eight species of parasites were collected from harbour seals from the German North Sea. Two anisakid nematodes (Pseudoterranova decipiens (sensu lato), Contracaecum osculatum (sensu lato) from the stomach, Otostrongylus circumlitus (Crenosomatidae) and Parafilaroides gymnurus (Filaroididae) from the respiratory tract, one filaroidid nematode (Acanthocheilonema spirocauda) from the heart, two acanthocephalans Corynosoma strumosum and C. semerme (Polymorphidae) from the intestine and the ectoparasite Echinophthirius horridus (Anoplura, Insecta) were found. Lungworm infection was the most prominent parasitological finding and secondary bacterial bronchopneumonia the most pathogenic lesion correlated with the parasites. Heavy nematode burdens in the respiratory tract were highly age‐related and more frequent in young seals. A positive correlation was observed between high levels of pulmonary infection and severity of bronchopneumonia. The prevalence of lungworms in this study was higher than in seals that died during the 1988/89 Phocine Distemper Virus epidemic, and prevalence of acanthocephalans and heartworms had decreased compared to findings from the die‐off. The metastrongyloid nematodes of porpoises and seals from German waters parasitising the respiratory tract were especially pathogenic and often caused secondary bacterial infections. In spite of the importance of lungworm disease for the health of wild populations and their clinical and epidemiological significance, the life cycle and biology of lungworms in the marine environment is still largely unknown. The ITS‐2 (rDNA) region of lungworms parasitising porpoises and seals were sequenced to characterise the different species. Molecular markers to identify larval nematode stages via in‐situ hybridisation in tissues of porpoise and seal prey were developed. Potential intermediate hosts from the North Sea were screened for larval stages of lungworms using the species‐specific traits of the ITS‐2. Histology and in‐situ hybridisation of tissue samples of flatfish showed larvae within the intestinal wall. Using larval ITS‐2 nucleotide sequences the nematode stages were identified as P. inflexus and P. gymnurus. Experimental infections of turbot (Psetta maxima) with live seal lungworm larvae (O. circumlitus) revealed second and third‐stage larvae of O. circumlitus in their intestinal tract. The results elucidated the life cycle of metastrongyloids of porpoises and seals and showed that they use vertebrate intermediate hosts. This thesis discovered new aspects of the life history of lungworm parasites of porpoises and seals by combining novel molecular techniques with methods from traditional parasitology. New information on parasite species and associated diseases in porpoises and seals improved the knowledge about the biology of parasites and hosts and our understanding of infection patterns. ZUSAMMENFASSUNG Parasitismus bei Wildtieren ist allgegenwärtig, zur Dynamik von Parasiteninfektionen und damit assoziierten Erkrankungen in marinen Säugetieren ist jedoch wenig bekannt. In dieser Arbeit wurde die Parasitenfauna von Schweinswal (Phocoena phocoena) und Seehund (Phoca vitulina) charakterisiert und ihr Einfluss auf den Gesundheitszustand der Wirte abgeschätzt. Zusätzlich sollte der bisher unbekannte Lebenszyklus ihrer Lungenwurmspezies erforscht werden. Parasitologische Untersuchungen wurden an Schweinswalen aus der deutschen Nord‐ und Ostsee und norwegischen Gewässern durchgeführt. Parasiten kamen hauptsächlich im Respirationstrakt vor und bestanden aus vier pseudaliiden Nematodenarten (Pseudalius inflexus, Torynurus convolutus, Halocercus invaginatus, Stenurus minor), einem ascaridoiden Nematoden (Anisakis simplex) und zwei Trematoden (Campula oblonga, Pholeter gastrophilus). H. invaginatus wurde zum ersten Mal in deutschen Gewässern beschrieben. Unterschiede in der Schwere des Befalls zwischen gestrandeten und beigefangenen Tieren sowie zwischen Schweinswalen aus verschiedenen Gebieten traten auf. Eine Korrelation zwischen Parasitenbefall und Gewebeläsionen in den betroffenen Organen konnte gezeigt werden. Lungenwurmprävalenz und die Intensität des Befalls nahm mit dem Alter der Wirtstiere zu, was auf eine horizontale Übertragung der Parasiten über das Nahrungsnetz schließen lässt. Die Daten ließen darauf schließen, dass die Infektionen langlebig waren und sich mit dem Alter akkumulierten. Das Vorkommen von Walläusen, Isocyamus delphinii (Crustacea: Amphipoda: Cyamidae), auf einem gestrandeten Schweinswal wurde beschrieben. Das abgemagerte Tier hatte mehrere, zum Teil vernarbte Wunden, an denen zahlreiche kleine Crustaceen saßen. Die Walläuse zeigten einen signifikanten sexuellen Dimorphismus und ihre Population wurde von männlichen Tieren dominiert. Die Läsionen in der Lunge des Tieres wurden als Todesursache und die Ektoparasiten nicht als Gefahr für den Gesundheitszustand des Wirtes angenommen. Die Ursache der Hautwunden blieb unklar, aber die Walläuse schienen mit den Wunden assoziiert und von ihnen abhängig zu sein. Bei diesem ersten ungewöhnlichen Vorkommen von I. delphinii auf einem Schweinwal aus deutschen Gewässern fand die Übertragung möglicherweise interspezifisch statt und die Hautwunden waren wahrscheinlich die Voraussetzung für die Walläuse um auf diesem Wirt zu überleben. Acht Parasitenspezies wurden in Seehunden aus der deutschen Nordsee isoliert: Zwei anisakide Nematoden (Pseudoterranova decipiens (sensu lato), Contracaecum osculatum (sensu lato) aus dem Magen, Otostrongylus circumlitus (Crenosomatidae) und Parafilaroides gymnurus (Filaroididae) aus dem Respirationstrakt, ein filaroidider Nematode (Acanthocheilonema spirocauda) aus dem Herz, zwei Acanthocephalen Corynosoma strumosum und C. semerme (Polymorphidae) aus dem Darm und der Ektoparasit Echinophthirius horridus (Anoplura, Insecta). Lungenwurminfektionen stellten den häufigsten parasitologischen Befund dar und sekundäre bakterielle Bronchopneumonie die pathogenste Läsion, die mit den Parasiten korreliert war. Schwerer Parasitenbefall war altersabhängig und besonders häufig in jungen Seehunden. Die Lungenwurmprävalenz in dieser Studie war höher als bei Seehunden, die während der Staupeepidemie 1988/89 starben, hingegen hatte die Prävalenz von Acanthocephalen und Herzwürmern abgenommen. Die metastrongyliden Nematoden von Schweinswal und Seehund waren besonders pathogen und verursachten häufig sekundäre bakterielle Infektionen. Trotz ihrer Bedeutung für den Gesundheitszustand wilder Populationen und ihrer klinischen und epidemiologischen Bedeutung ist ihr Lebenszyklus im Meer weitgehend unbekannt. Die ITS‐2 (rDNA) Region der Lungenwürmer von Schweinswalen und Seehunden wurde sequenziert, um die verschiedenen Spezies zu charakterisieren. Die spezies‐spezifischen Eigenschaften der Sequenzen wurden genutzt um potentielle Zwischenwirte auf Larvenstadien hin zu überprüfen. Molekulare Marker zur Identifizierung von Larvenstadien wurden entwickelt. Histologie und in‐situ Hybridisierung zeigten Nematodenlarven in der Darmwand von Plattfischen, die Larven wurden anhand ihrer ITS‐2 Region als P. inflexus und P. gymnurus identifiziert. Experimentelle Infektionen von Steinbutt (P. maxima) mit lebenden O. circumlitus Larven ergaben Zweit‐ und Drittlarven im Darmtrakt der Fische. Die Ergebnisse beleuchten den Lebenszyklus der Lungenwürmer von Schweinswalen und Seehunden und zeigen, dass sie vertebrate Zwischenwirte für ihre Übertragung nutzen. Diese Arbeit deckte neue Aspekte der Biologie von Parasiten mariner Säuger auf, indem sie neue molekulare Techniken mit traditioneller Parasitologie verknüpfte. Informationen über Parasitenspezies und assoziierte Krankheiten in den Wirtstieren verbesserte unser Wissen über Parasit‐Wirt Beziehungen und unser Verständnis der Infektionsmuster.