Transmission of lungworms of harbour porpoises and harbour seals: molecular tools determine potential vertebrate intermediate hosts

[Zoonotic potential of brucellosis in marine mammals]

Introduction

Brucellosis in marine mammals (cetacean and pinnipeds) has emerged in a very significant way during the last two decades. Currently Brucella ceti and Brucella pinnipedialis are the two recognized species in marine mammals, but available information is still limited. Several genotypes have been identified, and studies on the relationship between sequence type (ST) and organ pathogenicity or tropism have indicated differences in pathogenesis between B. ceti sequences in cetaceans. The zoonotic potential of this disease is based on the identification of the main sources of introduction and spread of Brucella spp. in the marine environment as well as on the factors of exposure of marine mammals and humans to the bacteria.

Bibliographic review

This article is a bibliographical review on marine mammal brucellosis, including the features, sources and transmission modes of each Brucella species, as well as their potential pathogenicity in animals and humans.

Conclusion

Different genotypes of marine Brucella spp have been isolated from marine mammal species but without any evidence of pathology induced by these bacteria. Associated lesions are variable and include subcutaneous abscesses, meningo-encephalomyelitis, pneumonia, myocarditis, osteoarthritis, orchitis, endometritis, placentitis and abortion. The isolation of marine B. spp from marine mammal respiratory parasites associated to lung injury has raised the intriguing possibility that they may serve as a vector for the transmission of this bacterium.The severity of marine B. spp remains unknown due to the lack of an estimate of the prevalence of this disease in marine mammals. The number of suspected human cases is still very limited. However, by analogy with other germs of the genus Brucella responsible for abortion in ruminants and for a febrile and painful state in human beings, prevention measures are essential. The significant increase in the number of strandings coupled with a high seroprevalence in certain species of marine mammals must be considered for people in direct or indirect contact with these animals. Ongoing epidemiological monitoring combined with extensive post-mortem examinations (necropsy, bacteriology and sequencing) of all species of stranded marine mammals would deepen knowledge on the zoonotic potential of marine Brucella species.

A systematic review of the diversity and virulence correlates of metastrongyle lungworms in marine mammals

Metastrongyle lungworms could be particularly detrimental for diving animals such as marine mammals; however, little is known of the drivers of pathogenic host–parasite relationships in this group. This systematic review analysed the diversity of metastrongyles in marine mammals and the host and parasite traits associated with virulence. There have been at least 40 species of metastrongyles described in 66 species of marine mammals. After penalization for study biases, Halocercus hyperoodoni, Otostrongylus circumlitus, Parafilaroides gymnurus, Halocercus brasiliensis and Stenurus minor were the metastrongyles with the widest host range. Most studies (80.12%, n = 133/166) reported that metastrongyles caused bronchopneumonia, while in the cardiovascular system metastrongyles caused vasculitis in nearly half of the studies (45.45%, n = 5/11) that assessed these tissues. Metastrongyles were associated with otitis in 23.08% (n = 6/26) of the studies. Metastrongyle infection was considered a potential contributory to mortality in 44.78% (n = 90/201) of the studies while 10.45% (n = 21/201) of these studies considered metastrongyles the main cause of death. Metastrongyle species with a wider host range were more likely to induce pathogenic effects. Metastrongyles can cause significant tissue damage and mortality in marine mammals although virulent host–parasite relationships are dominated by a few metastrongyle species with wider host ranges.

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.

Molecular phylogeny of the Pseudaliidae (Nematoda) and the origin of associations between lungworms and marine mammals

Metastrongyloid lungworms from the family Pseudaliidae infect the lungs and cranial sinuses of cetaceans worldwide, except Stenuroides herpestis, which exhibits a striking terrestrial association with the Egyptian mongoose, Herpestes ichneumon. Previous phylogenies of the Metastrongyloidea that included some (2-7) marine species of the Pseudaliidae confirmed that these species are closely related, but also grouped species of Parafilaroides (family Filaroididae) between the members of the Pseudaliidae. In this study we extracted DNA from representatives of all six genera of the Pseudaliidae and amplified the second internal transcribed spacer (ITS2) and cytochrome c oxidase subunit I (cox1) genes in order to investigate the concept of the Pseudaliidae as a monophyletic unit. Three species of Parafilaroides were also included in the analysis. Maximum Likelihood and Bayesian Inference analyses of the concatenated genes resulted in a well-supported clade including the marine pseudaliids, S. herpestis and Parafilaroides spp. These findings validate the status of S. herpestis as a pseudaliid species and support the inclusion of Parafilaroides in the Pseudaliidae. Although males of Parafilaroides spp. lack a copulatory bursa, this trait itself is highly variable in the Pseudaliidae, which include abursate species. Furthermore, life cycles seem to be closely similar between both taxa. When all the available phylogenetic data on the Metastrongyloidea were mapped of onto a phylogeny of the Laurasiatheria, there was a strong suggestion that the Pseudaliidae may have descended from ancestors infecting terrestrial carnivores, with odontocetes being colonized in the marine realm as a result of a host-switching event from pinnipeds through shared fish prey. The origin of the association between S. herpestis and mongooses remains uncertain.

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.

Specificity of Stenurus (Metastrongyloidea: Pseudaliidae) infections in odontocetes stranded along the north-west Spanish coast

Parasites extracted from the lungs and the pterygoid sinus complex of 6 species of odontocetes stranded along the north-west Spanish coast (Northeast Atlantic) between 2009 and 2019 were morphologically identified. The samples belonged to 14 specimens, including 3 harbour porpoises, Phocoena phocoena, 6 short-finned pilot whales, Globicephala macrorhynchus, 1 long-finned pilot whale, Globicephala melas, 1 Risso's dolphin, Grampus griseus, 1 striped dolphin, Stenella coeruleoalba and 2 bottlenose dolphins, Tursiops truncatus. All animals (14/14) were infected by nematodes of the genus Stenurus spp.; moreover, two of them presented a mixed lung nematode infection by Stenurus spp. and Halocercus spp., and another two a mixed infection by Stenurus spp. and the trematode Nasitrema spp. in the pterygoid sinuses. The morphological characterization of the Stenurus specimens revealed the existence of three different species: Stenurus minor, present in the pterygoid sinuses of harbour porpoises with a mean intensity of 43.0 ± 9.0; Stenurus globicephalae, in the pterygoid sinuses of pilot whales and the Risso's dolphin (370.3 ± 579.4); and Stenurus ovatus infecting bottlenose and striped dolphins’ lungs (47.7 ± 76.5). This is the first citation of S. minor and S. ovatus in odontoceti from the Galician coast. Nematodes of the genus Stenurus are frequent in odontocetes stranded along the north-west Spanish coast. A clear host-parasite association was observed between S. minor and the Phocoenidae family, between S. globicephalae and the subfamily Globicephalinae and between S. ovatus and subfamily Delphininae. Different trophic position and niche segregation may lead to different patterns of specificity.

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Stenurus is the most prevalent lungworm in odontoceti.

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First description of S. minor and S. ovatus in Galician waters.

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Short-finned whales are the most intensely infected odontocetes.

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Stenurus infection is favored by the greater length of the host.

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Stenurus spp show a clear pattern of specificity with their hosts.

PHYLOGENETIC ANALYSIS OF THE LUNGWORMS (NEMATODA: METASTRONGYLOIDEA) INFERRED USING NUCLEAR RIBOSOMAL AND MITOCHONDRIAL DNA SEQUENCES

Phylogenetic relationships among the mammal-parasitic lungworms (Metastrongyloidea) were inferred using small- and large-subunit ribosomal DNA sequences together with 12S ribosomal mtDNA sequences. Maximum parsimony and Bayesian inference methods were used from optimal alignments and those filtered for alignment ambiguity. Analysis of 30 ingroup sequences using ribosomal DNA sequences yielded a single most parsimonious tree. Monophyly of the Metastrongyloidea was supported, but there was no support for monophyly of any of the 7 families as they have been traditionally defined. Parafilaroides decorus, an abursate lungworm of pinnipeds currently classified in the Filaroididae, was nested within a clade containing members of the Pseudaliidae, parasites of cetaceans. The tree also shows clades somewhat resembling the traditional familial divisions of the Metastrongyloidea, but in all groups, paraphyletic relationships were recovered. In a combined analysis of nuclear rDNA and 12S mtDNA, maximum parsimony and Bayesian analyses showed similar patterns to those observed with only nuclear rDNA sequences. Based on the phylogeny, the respiratory tract was inferred to be the ancestral predilection site for Metastrongyloidea, with multiple evolutionary invasions of extrapulmonary sites such as sinuses, circulatory system, and meninges. Similarly, the ancestral host was inferred to be a carnivore with subsequent colonization events into marsupial, rodent, artiodactyl, pinniped, and cetacean hosts.

Pathological findings in bycaught harbour porpoises (Phocoena phocoena) from the coast of Northern Norway

Due to little prior knowledge, the present study aims to investigate the health status of bycaught harbour porpoises from the northernmost Arctic Norwegian coastline. Gross, histopathological and parasitological investigations were conducted on 61 harbour porpoises (Phocoena phocoena phocoena) accidentally captured in fishing gear from February to April 2017 along the coast of Northern Norway. Most animals displayed a good nutritional status, none were emaciated. Pulmonary nematodiasis (Pseudalius inflexus, Halocercus invaginatus and Torynurus convolutus) was found in 77% and associated with severe bronchopneumonia in 33% of the animals. The majority (92%) had parasites in the stomach and intestine (Anisakis simplex sensu stricto (s. s.), Pholeter gastrophilus, Diphyllobothrium stemmacephalum, Hysterothylacium aduncum and Pseudoterranova decipiens s. s.). The prevalence of gastric nematodiasis was 69%. In the 1st stomach compartment A. simplex s. s. was found in 30% of the animals, causing severe chronic ulcerative gastritis in 23%. Campula oblonga infected the liver and pancreas of 90% and 10% of the animals, respectively, causing severe cholangitis/pericholangitis/hepatitis in 67% and moderate pancreatitis in 10% of the animals. Mesenteric and pulmonary lymphadenitis was detected in 82% and 7% of the animals, respectively. In conclusion, the major pathological findings in the investigated Arctic porpoises were parasitoses in multiple organs with associated severe lesions, particularly in the lung, liver and stomach. The animals were generally well nourished and most showed freshly ingested prey in their stomachs. The present study indicates that the harbour porpoises were able to tolerate the detected parasitic burden and associated lesions without significant health problems.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Lungworm infections in harbour porpoises (Phocoena phocoena) in the German Wadden Sea between 2006 and 2018, and serodiagnostic tests

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.

Nematode Parasites in Baltic Sea Mammals, Grey Seal (Halichoerus grypus (Fabricius, 1791)) and Harbour Porpoise (Phocoena phocoena (L.)), from the German Coast

Purpose

Endoparasitic nematodes of six harbour porpoises Phocoena phocoena and four grey seals Halichoerus grypus, stranded at the eastern coast of the Baltic Sea in Germany in winter 2019, were analysed in order to identify nematode parasites and to compare with recent studies from the same area.

Methods

Endoparasitic nematodes were identified by using both morphological and molecular characters. The successfully obtained sequences of the rDNA marker regions ITS-1, 5.8S, ITS-2 from 29 anisakid and the rDNA marker region ITS-2 of 11 pseudalid nematodes were amplified.

Results

Analyses revealed the presence of three parasite species, the anisakid nematode Contracaecum osculatum from grey seals and the pseudalid nematodes Pseudalius inflexus and Stenurus minor from the harbour porpoises. Other anisakid nematodes regularly occurring in the Baltic Sea, e.g. Anisakis simplex or Pseudoterranova decipiens, were not found.

Conclusions

The prevalence of 100% and a severe parasite load in grey seals demonstrated a very high C. osculatum infection of Baltic Sea fish as their regular prey. Prevalence of 33% for parasites in harbour porpoises and minor infection rates, combined with a distinct lack of anisakid nematodes, are typical for the current situation of the porpoise parasite fauna in the Baltic Sea. Invasive parasite species as possible indicators for climate change could not be detected.

New host and geographical records for Parafilaroides normani (Nematoda: Filaroididae) Dailey, 2009 in South American fur seal, Arctocephalus australis, from southern Brazil

Lungworms are a common finding in seals and fur seals around the world. However, from existing records, the biogeographical distribution of filaroid helminths appears to be restricted, and these parasites are endemic in only certain areas and species, mainly in the Northern Hemisphere. The occurrence of infection in pinniped species in the Southern Hemisphere is scarce. The objective of this work is to verify the prevalence of lungworms in Arctocephalus australis in waters off the southern coast of Brazil. Twenty subadult specimens of A. australis found recently dead on the southern coast of Brazil were necropsied and their lungs were examined. Parasitic cysts were found in only one specimen (prevalence of 5%). The helminths were morphologically identified as Parafilaroides normani (Metastrongyloidea: Filaroididae). This helminth species has been reported in pinnipeds from Australia, New Zealand and South Africa. This is the first record of P. normani in A. australis and for the western South Atlantic, providing additional data regarding the biogeographic distribution of the parasite.

Health assessment of harbour porpoises (PHOCOENA PHOCOENA) from Baltic area of Denmark, Germany, Poland and Latvia

Harbour porpoise (Phocoena phocoena), the only resident cetacean species of the Baltic Sea is formed of two subpopulations populations, occurring in the western Baltic, Belt Seas and Kattegat and the Baltic Proper, respectively. Harbour porpoises throughout these areas are exposed to a large number of human activities causing direct and indirect effects on individuals, that might also harm this species on a population level. From Latvia, Poland, Germany and Denmark 385 out of 1769 collected dead harbour porpoises were suitable for extensive necropsy. The animals were collected between 1990 and 2015 and were either by-caught or found dead on the coastline. Following necropsies, histopathological, microbiological, virological and parasitological investigations were conducted. Females and males were equally distributed among the 385 animals. Most animals from the different countries were juveniles between 3 months and 3 years old (varying between 46.5 and 100% of 385 animals per country). The respiratory tract had the highest number of morphological lesions, including lungworms in 25 to 58% and pneumonia in 21 to 58% of the investigated animals. Of those with pneumonia 8 to 33% were moderate or severe. The alimentary, hearing, and haematopoietic systems had inflammatory lesions and parasitic infections with limited health impact. 45.5 to 100% of the animals from the different countries were known by-caught individuals, of which 20 to 100% varying between countries had netmarks. Inflammatory lesions, especially in the respiratory tract were found in higher numbers when compared to control populations in areas with less human activities such as arctic waters. The high number of morphological changes in the respiratory tract and of bycatches especially among immature animals before reaching sexual maturity is of serious concern, as well as the low number of adult animals among the material. Data on health status and the causes of death are valuable for management. A next step in this regard will combine data from health and genetic investigations in order to detect differences between the two populations of the Baltic.

The taxonomic status of Skrjabinalius guevarai Gallego & Selva, 1979 (Nematoda: Pseudaliidae) and the synonymy of Skrjabinalius Delyamure, 1942 and Halocercus Baylis & Daubney, 1925

Within the cetacean lungworm family Pseudaliidae Raillet & Henry, 1909, the distinction between the two genera of the subfamily Halocercinae Delamure, 1952, i.e. Halocercus Baylis & Daubney, 1925 and Skrjabinalius Delyamure, 1942, is principally based on the structure and shape of the male copulatory bursa. In species of Halocercus, the bursa is unlobed, whereas in the two species included in Skrjabinalius, S. cryptocephalus Delyamure, 1942 and Skrjabinalius guevarai Gallego & Selva, 1979, the bursa is described as clearly lobed. During a parasitological analysis of cetaceans from the Spanish Mediterranean, we collected a number of specimens of S. guevarai with variable levels of bursal lobulation, including individuals with unlobed bursae. Examination of voucher specimens of the type-species of Halocercus, H. delphini Baylis & Daubney, 1925, collected from cetaceans in the North-East Atlantic revealed the same variations in bursal shape, and the same arrangement of bursal rays and papillae. A morphometric comparison did not reveal substantial differences between both species. Moreover, Maximum Likelihood and Bayesian Inference analyses of the second internal transcribed spacer (ITS2) sequences of 11 specimens of S. guevarai and one of H. delphini grouped both species together, regardless of bursal shape, in a highly supported clade within the Pseudaliidae. Accordingly, we consider S. guevarai as a junior synonym of H. delphini. The great variability found in bursal lobulation in the type-species of Halocercus invalidates the use of this trait as a genus-level diagnostic character and, therefore, Skrjabinalius should also be considered synonymous with Halocercus.

Surprisingly long body length of the lungworm Parafilaroides gymnurus from common seals of the Dutch North Sea

Lungworms of the genera Parafilaroides and Otostrongylus are responsible for parasitic bronchopneumonia, the foremost disease of eastern Atlantic common seals (EACS, Phoca vitulina vitulina) in the Dutch North Sea. Recently, there have been increased reports of lungworm cases and observations of unusually long Parafilaroides sp. adults in this location. The initial aim of this study was to confirm the identity of the Parafilaroides species infecting this population. Parafilaroides are usually small and delicate, making them difficult to extract from host tissue, and there is often difficulty accessing fresh specimens for morphological study. The large size of the Dutch worms and the accessibility of specimens from numerous animals enabled the description and measurement of many intact specimens (N = 64) from multiple host animals (N = 20). Species identity was confirmed by targeted sequencing of ribosomal and mitochondrial DNA amplicons from a subset of worms. Worm morphology was consistent with descriptions for P. gymnurus, but the mature females were 1.9-fold and 3.4-fold longer than those recovered from French EACS (P ≤ 0.001) and Canadian western Atlantic common seals (Phoca vitulina concolor; P ≤ 0.0001). They were also significantly longer than mature female P. gymnurus described from other seal species, with the exception of those from harp seals of Les Escoumins, Quebec. We suggest that intraspecific genetic differences in P. gymnurus and the environment within the host could contribute to the variation reported here. This study is the first to describe P. gymnurus using morphological and molecular methods and should serve as a reference for identification of the species.

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

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

Morphological and Pathological Findings in the Middle and Inner Ears of Harbour Porpoises (Phocoena phocoena)

Hearing represents the major sense in harbour porpoises (Phocoena phocoena) and impairment of hearing has a great impact on the survival of these animals. In this communication, some anatomical and histological aspects of the tympanoperiotic complex of harbour porpoises are presented. In addition, the ears of 21 incidentally bycaught or stranded freshly dead harbour porpoises of different age groups and sex were investigated histologically. At the entrance to the middle ear cavity, mucosa-associated lymphoid tissue was present that was often hyperplastic in juvenile (9/10) and adult individuals (7/8). Solitary lymphoid follicles were additionally found in the corpus cavernosum and adjacent to the stapedius muscle in single porpoises. The nematode Stenurus minor represented the most common pathogen observed in the middle ear cavity of juvenile and adult harbour porpoises and the parasite was associated with chronic inflammation with metaplastic and hyperplastic epithelial changes. An unusual bone formation at the attachment of the corpus cavernosum to the perioticum was a common finding, even in young individuals. Whether this represents a normal structure or a metaplastic change remains undetermined. Acute haemorrhages in the cochlea and/or the tympanic cavity occurred in all animals and were most likely agonal changes. Single porpoises suffered from purulent otitis media, mycotic otitis media with osteolysis or chronically fractured tympanic bones, likely causing impairment of hearing that may have contributed to by-catch. There was no evidence that stranding in five porpoises was associated with the aural changes. Histological examination of the ears in harbour porpoises is a valuable part of the assessment of their health status. Damage to hearing structures may explain starvation due to impaired ability to catch prey or unusual behaviour such as stranding or entanglement in nets.

Transmission and Predictors of Burden of Lungworms of the Striped Dolphin (Stenella coeruleoalba) in the Western Mediterranean

Pseudaliid lungworms infect the lungs and sinuses of cetaceans. Information on the life cycle and epidemiology of pseudaliids is very scarce and mostly concerns species that infect coastal or inshore cetaceans. Available evidence indicates that some pseudaliids are vertically transmitted to the host, whereas others are acquired via infected prey. We documented pseudaliid infections in an oceanic cetacean, the striped dolphin (Stenella coeruleoalba) in the western Mediterranean, and investigated the possibilities of vertical vs. horizontal transmission and the potential influence of host body size, sex, and season on infection levels. We found two species of lungworm in 87 dolphins that stranded along the Spanish Mediterranean coast between 1987 and 2018. One or two larvae of Stenurus ovatus were found in three adult dolphins. Larger numbers of larvae and adults of Skrjabinalius guevarai were collected in 51 dolphins, including unweaned calves. These observations suggested that Skrjabinalius guevarai could be vertically transmitted. The abundance of Skrjabinalius guevarai increased significantly with host size, which suggested that it could be trophically transmitted, as well, with larger hosts consuming more infected prey. Infection levels peaked in spring, outside of the calving season, which is likely a reflection of a seasonal shift in dolphin diet. In summary, results indicate that Skrjabinalius guevarai was capable of both vertical and horizontal transmission, but future research should be directed at clarifying the potential mechanics behind transmission and intermediate hosts.

Cytokine expression and lymphocyte proliferative capacity in diseased harbor porpoises (Phocoena phocoena) - Biomarkers for health assessment in wildlife cetaceans

Harbor porpoises (Phocoena phocoena) in the North and Baltic Seas are exposed to anthropogenic influences including acoustic stress and environmental contaminants. In order to evaluate immune responses in healthy and diseased harbor porpoise cells, cytokine expression analyses and lymphocyte proliferation assays, together with toxicological analyses were performed in stranded and bycaught animals as well as in animals kept in permanent human care. Severely diseased harbor porpoises showed a reduced proliferative capacity of peripheral blood lymphocytes together with diminished transcription of transforming growth factor-β and tumor necrosis factor-α compared to healthy controls. Toxicological analyses revealed accumulation of polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (DDE), and dichlorodiphenyltrichloroethane (DDT) in harbor porpoise blood samples. Correlation analyses between blood organochlorine levels and immune parameters revealed no direct effects of xenobiotics upon lymphocyte proliferation or cytokine transcription, respectively. Results reveal an impaired function of peripheral blood leukocytes in severely diseased harbor porpoises, indicating immune exhaustion and increased disease susceptibility.

Brucella pinnipedialis in lungworms Parafilaroides sp. and Pacific harbor seals Phoca vitulina richardsi: proposed pathogenesis

Brucella spp. were first isolated from marine mammals in 1994 and since have been described in numerous pinniped and cetacean species with nearly global distribution. Microscopic, electron microscopic, or culture results have shown lungworms in harbor seals to be infected with brucellae, suggesting that the lungworms may serve a role in this infection. In this study, we reviewed archived and more recent case material from 5 Pacific harbor seals from Washington State (USA) with evidence of B. pinnipedialis infection in the lungworm Parafilaroides sp. Twenty-two sections of lung containing approximately 220 Parafilaroides sp., stained with an immunohistochemical technique using antibody to B. abortus, showed approximately 80 (36%) infected nematodes. A few brucellae were also present in lung parenchyma in proximity to nematodes. Infection was present in the first- and fourth-stage larvae in the seal lung and intestines, as well as in the male and female reproductive organs of adult nematodes. Infected sperm deposits in the nematode uterus were suggestive of venereal transmission between lungworms. Massive infection of some degenerate adult lungworms and evidence of degeneration of some developing larvae in utero were observed. Based on these observations, we suggest that Parafilaroides sp., rather than the Pacific harbor seal Phoca vitulina richardsi, is the preferred host of B. pinnipedialis infection.

A novel quantitative real-time PCR diagnostic assay for seal heartworm (Acanthocheilonema spirocauda) provides evidence for possible infection in the grey seal (Halichoerus grypus)

The distinct evolutionary pressures faced by Pinnipeds have likely resulted in strong coevolutionary ties to their parasites (Leidenberger et al., 2007). This study focuses on the phocid seal filarial heartworm species Acanthocheilonema spirocauda. A. spirocauda is known to infect a variety of phocid seals, but does not appear to be restricted to a single host species (Measures et al., 1997; Leidenberger et al., 2007; Lehnert et al., 2015). However, to date, seal heartworm has never been reported in grey seals (Halichoerus grypus) (Measures et al., 1997; Leidenberger et al., 2007; Lehnert et al., 2015). The proposed vector for seal heartworm is Echinophthirius horridus, the seal louse. Seal lice are known to parasitize a wide array of phocid seal species, including the grey seal. With the advent of climate change, disease burden is expected to increase across terrestrial and marine mammals (Harvell et al., 2002). Accordingly, increased prevalence of seal heartworm has recently been reported in harbor seals (Phoca vitulina) (Lehnert et al., 2015). Thus, the need for improved, rapid, and cost-effective diagnostics is urgent. Here we present the first A. spirocauda-specific rapid diagnostic test (a quantitative real-time PCR assay), based on a highly repetitive genomic DNA repeat identified using whole genome sequencing and subsequent bioinformatic analysis. The presence of an insect vector provides the opportunity to develop a multifunctional diagnostic tool that can be used not only to detect the parasite directly from blood or tissue specimens, but also as a molecular xenomonitoring (XM) tool that can be used to assess the epidemiological profile of the parasite by screening the arthropod vector. Using this assay, we provide evidence for the first reported case of seal heartworm in a grey seal.

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.

Molecular identification of potential intermediate hosts of Aulonocephalus pennula from the order Orthoptera

Aulonocephalus pennula is a heteroxenous nematode that commonly infects a declining game bird, the northern bobwhite quail (Colinus virginianus). There is a lack of information on the life cycle of A. pennula and the potential effects of infection on bobwhites. In order to better understand the life cycle of this parasite, various species from the order Orthoptera were collected from a field site in Mitchell County, Texas. Using polymerase chain reaction (PCR), nine potential intermediate hosts were identified from the 35 orthopteran species collected. Later, ten live specimens were collected to identify larvae within the potential intermediate hosts. Larvae were present in three of these and were sent for sequencing. Similarly, the presence of larvae was confirmed from extra tissues of samples identified as positive with PCR. This was the first study to document potential intermediate hosts, but future studies are needed to confirm that these species are capable of transmitting infection to bobwhite. However, this study demonstrates that PCR has increased sensitivity and may be a valuable tool when determining intermediate hosts.

Quantifying parasite presence in relation to biological parameters of harbour porpoises Phocoena phocoena stranded on the Dutch coast

Harbour porpoises are often found to be infected by endoparasites in several organs including the lungs and stomach as well as the heart, liver and ears. Nevertheless there is still little knowledge about the impact, ecology, transmission, and virulence of these parasitic infections. Here, we profile the presence of parasites in 4 frequently infected organs (lungs, stomach, liver and ears) in relation to biological parameters of harbour porpoises stranded along the Dutch coastline between December 2008 and December 2013. We found that parasites were common, with prevalence of 68% in lungs, 74.4% in ears, 26% in stomach and 23.5% in liver. We used generalised linear models to further quantify parasite presence in relation to biological data gathered during necropsy (sex, body length and nutritive condition). Body length (used as a proxy for age) was significant in explaining parasite presence for all organs with increasing probability of having the parasite with increasing body length. For the parasitic infections in the ears and stomach the nutritive condition was an additional significant factor, with a higher probability of parasite presence in porpoises in a poorer nutritive condition. The results of this study can be used as a baseline for assessing parasite presence in harbour porpoises and are a first step towards linking parasite infections to basic biological data gathered during necropsy.

Population- and growth-related differences in helminthic fauna of finless porpoises (Neophocaena asiaeorientalis) in five Japanese populations

A survey of helminths and ectoparasites, including epizoits, was conducted in narrow-ridged finless porpoises (Neophocaena asiaeorientalis) from Japanese five populations using dead stranded or incidentally caught animals. In total, 13 helminth species were found (6 nematodes, 4 trematodes, 2 cestodes and 1 acanthocephalan) in 137 porpoises. A new location record of Stenurus nanjingensis and a new host record of Tetrabothrius sp. were obtained. Eight species of helminth were considered common in the Japanese populations of the finless porpoise: Pharurus sunameri, Pharurus asiaeorientalis, Nasitrema spathulatum, Nasitrema sunameri, Halocercus pingi, Halocercus sunameri, Campula oblonga and Synthesium elongatum. No anisakid nematodes were found. N. spathulatum was found only in the western waters of the Seto Inland Sea. Low prevalence of C. oblonga in the Omura Bay was demonstrated. H. pingi was mostly found in very young porpoises before starting to eat prey, indicating prenatal or transmammary infection. However, a congeneric species, H. sunameri, mainly infected weaned porpoises, indicating that these two species possess different transmission pathways. This study provides information on the geographical distribution and prevalence of helminth parasites in finless porpoises off the Japanese coast.

Experimental Challenge of Atlantic Cod (Gadus morhua) with a Brucella pinnipedialis Strain from Hooded Seal (Cystophora cristata)

Pathology has not been observed in true seals infected with Brucella pinnipedialis. A lack of intracellular survival and multiplication of B. pinnipedialis in hooded seal (Cystophora cristata) macrophages in vitro indicates a lack of chronic infection in hooded seals. Both epidemiology and bacteriological patterns in the hooded seal point to a transient infection of environmental origin, possibly through the food chain. To analyse the potential role of fish in the transmission of B. pinnipedialis, Atlantic cod (Gadus morhua) were injected intraperitoneally with 7.5 x 10⁷ bacteria of a hooded seal field isolate. Samples of blood, liver, spleen, muscle, heart, head kidney, female gonads and feces were collected on days 1, 7, 14 and 28 post infection to assess the bacterial load, and to determine the expression of immune genes and the specific antibody response. Challenged fish showed an extended period of bacteremia through day 14 and viable bacteria were observed in all organs sampled, except muscle, until day 28. Neither gross lesions nor mortality were recorded. Anti-Brucella antibodies were detected from day 14 onwards and the expression of hepcidin, cathelicidin, interleukin (IL)-1β, IL-10, and interferon (IFN)-γ genes were significantly increased in spleen at day 1 and 28. Primary mononuclear cells isolated from head kidneys of Atlantic cod were exposed to B. pinnipedialis reference (NCTC 12890) and hooded seal (17a-1) strain. Both bacterial strains invaded mononuclear cells and survived intracellularly without any major reduction in bacterial counts for at least 48 hours. Our study shows that the B. pinnipedialis strain isolated from hooded seal survives in Atlantic cod, and suggests that Atlantic cod could play a role in the transmission of B. pinnipedialis to hooded seals in the wild.

Lungworm seroprevalence in free-ranging harbour seals and molecular characterisation of marine mammal MSP

Harbour seals (Phoca vitulina) are frequently infected with the lungworms Otostrongylus circumlitus and Parafilaroides gymnurus. The infection is often accompanied by secondary bacterial infections and can cause severe bronchopneumonia and even death in affected animals. Hitherto, the detection of lungworm infections was based on post mortem investigations from animals collected within stranding networks and a valid detection method for live free-ranging harbour seals was not available. Recently, an ELISA was developed for detecting lungworm antibodies in harbour seal serum, using major sperm protein (MSP) of the bovine lungworm, Dictyocaulus viviparus as recombinant diagnostic antigen. To determine lungworm seroprevalence in free-ranging harbour seals, serum was taken from four different seal age groups (n = 313) resulting in an overall prevalence of 17.9% (18.9% of males, 16.7% of females). 0.7% of harbour seals up to six weeks of age were seropositive, as were 89% of seals between six weeks and six months, 53.6% between six and 18 months and 24.2% of seals over 18 months of age. In the 18 months and over age group, seropositive animals showed statistically significant reductions in body weight (P = 0.003) and length (P < 0.001). Sera from lungworm infected harbour seals in rehabilitation (n = 6) revealed that duration of antibody persistence may be similar to that of lungworm infected cattle, but further studies are needed to confirm this. Phylogenetic analyses of MSP sequences of different marine and terrestrial mammal parasitic nematodes revealed that lungworm MSP of the genus Dictyocaulus (superfamily Trichostrongyloidea) is more closely related to metastrongylid marine mammal lungworms than to trichostrongylid nematodes of terrestrial hosts.

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First study on lungworm seroprevalence in live free-ranging harbour seals.

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Total seroprevalence was 17.9%, but age-dependent differences were observed.

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Six weeks to six months old seals showed highest prevalences (89% positives).

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Seropositive adult seals showed significantly reduced body weight and length.

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Phylogenetic tree construction using MSP of marine and terrestrial mammal parasites.

A recombinant antigen-based enzyme-linked immunosorbent assay (ELISA) for lungworm detection in seals

BACKGROUND

Pinnipeds are frequently infected by the lungworms Otostrongylus circumlitus and Parafilaroides gymnurus (Metastrongyloidea). Infections are frequently associated with secondary bacterial bronchopneumonia and are often lethal. To date, a reliable lungworm diagnosis in individual seals is only possible during necropsy as examination of faeces collected from resting places does not allow assignment to individuals. Therefore, a diagnostic tool for lungworm detection in living seals is desirable for monitoring health of seals in the wild and in captivity. Previously, an ELISA based on recombinant bovine lungworm major sperm protein (MSP) as diagnostic antigen was developed for lungworm diagnosis in cattle. In the present study, this test was adapted for detection of antibodies against lungworms in harbour (Phoca vitulina) and grey seals (Halichoerus grypus). Furthermore, sera of northern elephant seals (Mirounga angustirostris) were tested to evaluate whether the harbour/grey seal ELISA is suitable for this seal species as well.

METHODS

For ELISA evaluation, lungworm-positive and -negative sera of harbour and grey seals were analysed using horseradish peroxidase (HRP)-conjugated Protein A as secondary antibody. Optical density was measured and a receiver operating characteristic (ROC) analysis was performed to determine a cut-off value. Potential cross-reactions were examined by testing serum of seals positive for gastrointestinal and heart nematodes, but negative for lungworm infections. In addition, sera of northern elephant seals were analysed.

RESULTS

Harbour and grey seal serum samples showed significant differences in optical density (OD) between serum of infected and uninfected animals resulting in a cut-off value of 0.422 OD with a specificity of 100% (95% CI: 87.23-100%) and a sensitivity of 97.83% (95% CI: 88.47-99.94%). Cross-reactions with heart or gastrointestinal nematodes were not observed. Analysis of northern elephant seal samples resulted in detection of antibodies in animals positive for lungworm larvae at faecal examination.

CONCLUSIONS

The ELISA presented is a valuable method for detection of lungworm infections in live harbour and grey seals, providing a monitoring tool to reveal epidemiological dynamics of lungworm infections during health surveillance in free-ranging seals. Furthermore, ELISA results may aid institutions with harbour and grey seals under human care on decisions regarding anthelminthic treatment of individual animals.

Role of Crassicauda sp. in natural mortality of pantropical spotted dolphins Stenella attenuata: a reassessment

Evaluating the effect of parasites on population size is essential for designing management and conservation plans of wild animal populations. Although knowledge in this area is scarce in cetaceans, current evidence suggests that species of the nematode genus Crassicauda may play an important regulatory role in some populations. In the present study, a semiparametric regression technique was applied to a previously published dataset to re-examine the role of Crassicauda sp. in natural mortality of pantropical spotted dolphins Stenella attenuata. The resulting model indicated parasite-induced mortality at ages between 6.5 and 9 yr and at roughly 12 yr. The maximum mortality estimates obtained could represent 2 to 4% of natural mortality in dolphins 6 to 8 yr old. This estimate is substantially smaller than previously published values, but in contrast with previous research, our model provides clear statistical evidence for parasite-induced mortality because the bootstrapped 95% confidence intervals of the estimated mortality rates excluded the 0 value. We also evaluated, through simulations, how potential sampling biases of infected dolphins could overestimate parasite-induced mortality. Small differences in sampling selectivity between infected and uninfected animals could substantially reduce the mortality estimates. However, the simulated models also supported the notion of statistically significant mortality in juvenile dolphins. Given that dolphins older than 16 yr were poorly represented in the dataset, further research is needed to establish whether Crassicauda sp. causes meaningful mortality for population dynamics among adult individuals.

A review of Brucella infection in marine mammals, with special emphasis on Brucella pinnipedialis in the hooded seal (Cystophora cristata)

Brucella spp. were isolated from marine mammals for the first time in 1994. Two novel species were later included in the genus; Brucella ceti and Brucella pinnipedialis, with cetaceans and seals as their preferred hosts, respectively. Brucella spp. have since been isolated from a variety of marine mammals. Pathological changes, including lesions of the reproductive organs and associated abortions, have only been registered in cetaceans. The zoonotic potential differs among the marine mammal Brucella strains. Many techniques, both classical typing and molecular microbiology, have been utilised for characterisation of the marine mammal Brucella spp. and the change from the band-based approaches to the sequence-based approaches has greatly increased our knowledge about these strains. Several clusters have been identified within the B. ceti and B. pinnipedialis species, and multiple studies have shown that the hooded seal isolates differ from other pinniped isolates. We describe how different molecular methods have contributed to species identification and differentiation of B. ceti and B. pinnipedialis, with special emphasis on the hooded seal isolates. We further discuss the potential role of B. pinnipedialis for the declining Northwest Atlantic hooded seal population.