Causes of mortality and non-fatal conditions among grey seals (Halichoerus grypus) found dead on the coasts of England, Wales and the Isle of Man

Hepatic Amyloidosis in a Chronically Entangled Grey Seal (Halichoerus grypus)

Grey seal (Halichoerus grypus) entrapment in fishing gear is well documented, consisting of two forms: peracute underwater entrapment and chronic entanglement. We now highlight a previously undescribed sequela to chronic entanglement in a female grey seal estimated to be at least 2 years of age. The animal was first observed in September 2018 on the coast of north Cornwall, southwest England, with a large encircling neck wound consistent with monofilament net entanglement. In April 2021, it was admitted for attempted rehabilitation but had to be euthanized after 9 days due to clinical deterioration despite treatment. At post-mortem examination, the seal was in poor nutritional state, the nose to flipper length was low for its estimated age and the liver was markedly enlarged, pale and friable in texture with evidence of recent and previous hepatic haemorrhage. Histopathology revealed hepatic amyloidosis and evidence of amyloid in one kidney and one adrenal gland. Proteomic analysis of microdissected amyloid from the liver indicated type AA amyloid. Chronic entanglement is the most plausible cause of AA amyloidosis in this animal, indicating that amyloidosis should be considered as a pathological sequela and welfare concern associated with chronic entanglement of grey seals.

Pathology of grey seals Halichoerus grypus in southwest England including pups in early rehabilitation

Few investigations have examined the pathology of grey seals Halichoerus grypus in southwest England, where it is the most abundant marine mammal. Here, primary pathological findings are presented from 107 post-mortem examinations of grey seals in southwest England between 2013 and 2020. Over three-quarters were pups in their first year of life; the origins of the carcasses reflected the known breeding season and breeding sites of grey seals in the region. Trauma was the most common primary pathological finding (n = 49), followed by infectious disease (n = 36). Traumatic findings included fisheries-related trauma (n = 15), other acute physical traumas (n = 15) and other chronic traumas (n = 19). Infectious disease findings included respiratory infections (n = 21) and gastrointestinal infections (n = 9). There was no difference in the primary pathological findings for seals found dead or that died or were euthanased on the day they were found compared to those dying in early rehabilitation, suggesting that it is appropriate to include findings from seals in early rehabilitation in studies of wild grey seal pathology. Seals that had not been frozen before post-mortem examination were nearly twice as likely to have a primary pathological finding of infectious disease or trauma than those that had been frozen, highlighting the need, wherever possible, to avoid freezing seals prior to post-mortem examination.

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.

Pathology and epidemiology of nasopulmonary acariasis (Halarachne sp.) in southern sea otters (Enhydra lutris nereis)

Halarachne sp. nasal mites infest harbor seals (Phoca vitulina) and southern sea otters (Enhydra lutris nereis) in California, but little is known about the pathophysiology of these infestations, or risk factors for exposure. To investigate these questions, a retrospective case-control study was performed using necropsy data from 70 mite-infested sea otters, and 144 non-infested controls. Case records for sea otters examined by pathologists from February 1999 through May 2015 were examined to assess risk factors for infestation, and lesions associated with nasopulmonary acariasis. Animals with a history of captive care within 10 days of death or carcass recovery were 3.2 times more likely to be infested with nasopulmonary mites than those with no history of recent rehabilitation. Sea otters stranding within 1 km of Elkhorn Slough in Monterey Bay were 4.9 times more likely to be infested with nasal mites than other areas; this site is characterized by high sea otter contact with sympatric harbor seals (a common host for Halarachne sp.), and a comparatively large population of rehabilitated and released sea otters. Aged adult otters were 9.4 times more likely to be infested than younger animals, and sea otters with nasopulmonary acariasis were 14.2 times more likely to have upper respiratory inflammation than un-infested animals. Additional findings in otters with nasopulmonary acariasis included lower respiratory tract bacterial infections, presence of medium-sized and/or fresh nose wounds at necropsy (indicators of recent face-to-face interaction between otters during copulation or fighting), and turbinate bone erosion. Our findings, although preliminary, suggest that captive rehabilitation and close contact with harbor seals could facilitate nasopulmonary mite transmission to sea otters. We also identified a high-risk zone for nasopulmonary acariasis in sea otters. We also provide preliminary data to suggest that nasopulmonary mite infestations can cause significant respiratory pathology in sea otters.

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Our data illustrates that nasopulmonary mites can be pathogenic for sea otters.

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High mite loads were associated with captive care, fresh nose wounds, and females.

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Mite-infested otters were 14 times more likely to have nasopharyngeal inflammation.

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Aged adult otters were 9 times more likely to be infested than other age groups.

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Otters hospitalized within 10 days of death were 3 times more likely to be infested.

Prevalence of Presenting Conditions in Grey Seal Pups (Halichoerus grypus) Admitted for Rehabilitation

A retrospective survey was performed on the presenting conditions of 205 live grey seal pups (Halichoerus grypus) admitted to the Cornish Seal Sanctuary in Gweek, United Kingdom between May 2005 and March 2011. The purpose of the survey was to examine the prevalence of various presenting signs at the sanctuary. The presenting signs were classified into nine non-mutually exclusive categories: ocular disorders, nasal disorders, oral disorders, respiratory disorders, orthopaedic disorders, puncture wounds, abrasions, netting injuries, and onychia. The sex ratio of seal pups in this study was 1.35 males per female. Of the 205 examined for rehabilitation, 22 (10.73%) did not survive to release. 68.78% of grey seal pups presented with puncture wounds, 47.80% with respiratory disorders, 46.34% with ocular disorders, 42.63% malnourished, 36.59% with abrasions, 25.37% with oral disorders, 23.90% with nasal disorders, 11.71% with orthopaedic disorders, 9.27% with onychia, and 3.41% presented with netting injuries. 52% were normothermic, 42% were hyperthermic, and 5% were hypothermic. Associations between gender, outcome of rehabilitation, hospitalisation time and presenting disorders were examined. In addition, admissions rates were found to display seasonality. The results of this study will aid in future preparation of grey seal rehabilitation facilities.

Entanglement of grey seals Halichoerus grypus at a haul out site in Cornwall, UK

Entanglement in marine debris has been internationally recognised as a potential threat to marine species. Sightings records and a photo identification catalogue from a haul out site in southwest England were used to establish entanglement records for grey seals Halichoerus grypus. Between 2004 and 2008 the annual mean entanglement rates varied from 3.6% to 5%. The maximum recapture period for entangled seals compared to paired control seals was significantly less (p=0.045) suggesting an increased mortality rate for affected seals. Of the 58 entangled cases in the catalogue, 64% had injuries that were deemed serious. Of the 15 cases where the entangling debris was visible, 14 were entangled in fisheries materials. The entanglement reported at this site could indicate a high rate of mortality and should be monitored carefully. On a more immediate level, entanglement represents a welfare issue for the affected animals.

Patterns of stranding and mortality in common seals (Phoca vitulina) and grey seals (Halichoerus grypus) in The Netherlands between 1979 and 2008

Pathological examination of stranded marine mammals provides information on the causes of mortality in their populations. Patterns of stranding and causes of death of dead-stranded seals on the Dutch coast were analyzed over a 30-year period (1979-2008). Stranding data (n=1,286) and post-mortem data (n=379) from common seals (Phoca vitulina) and grey seals (Halichoerus grypus) found dead, or that died before admission to rehabilitation, were obtained from the Seal Rehabilitation and Research Centre database. Data for the years 1988 and 2002, when mass mortality occurred due to phocine distemper virus epidemics, were excluded. Common seal stranding increased from one to nearly 100 per year over this period. This coincides with the increase in the number of common seals in Dutch waters over recent decades. Grey seal stranding increased gradually from one to about 40 per year over the period, reflecting recolonization of Dutch waters by this species. For both species, the trend in stranding of dead seals was found to be in line with that of seals observed in Dutch waters during aerial surveys and did not provide any indications of a relative change in the stranding rate of dead seals. The total monthly stranding rates peaked at more than 120 in June and July for common seals and at nearly 60 in January for grey seals. This coincides with the pupping periods of the two species. Besides phocine distemper, the most common causes of death in investigated common seals (n=286) were by-catch (confirmed and inferred) (19%), pup starvation (7%), intestinal volvulus (7%) and parasitic bronchopneumonia (6%). The most common causes of death in investigated grey seals (n=93) were by-catch (confirmed and inferred) (15%), pup starvation (11%) and trauma (5%). The relative occurrence of by-catch significantly decreased over time for grey seals, but not for common seals. Common seals were affected by infectious disease significantly more often than grey seals, mainly because of a higher occurrence of parasitic pneumonia. Phocine distemper caused mass mortalities among common seals, but not among grey seals. These findings in dead-stranded seals differ in part from those reported elsewhere in live-stranded seals, for which pup starvation and parasitic bronchopneumonia were the main causes of stranding. A substantial proportion of seals in Dutch waters die from causes related to human activity. Continued monitoring of stranding patterns and causes of death is warranted for early detection of changes and the possibility of taking timely management actions.

Naso-pharyngeal mites Halarachne halichoeri (Allman, 1847) in Grey seals stranded on the NW Spanish Atlantic Coast

In North Atlantic European waters, the nasal mite Halarachne halichoeri has been described affecting Grey seals (Halichoerus grypus) producing different levels of respiratory disease. This study provides data on the prevalence, clinical signs and produced macro-pathology of this parasite mite infecting juvenile wild Grey seals stranded in North-Western Spanish coast. Among the 25 seals examined during the study, a total of 19 had nasal mites in their respiratory upper ways, including adult and larval stages. This represented a percentage of prevalence of 76 ± 8.37. All the live positive seals presented a typical clinical symptomatology associated to upper respiratory tract infections. In dead positive seals, a light to intense sinusitis could be diagnosed macroscopically. The presence of the parasite in the nasal sinuses appears as the primary cause of the high respiratory tract symptomatology presented in most of the juvenile seals stranded in the north coast of Spain. Ultrastructural characterization by scanning electronic microscopy (SEM) has confirmed the taxonomic status of the mite. This identification of H. halichoeri represents the first description of the occurrence of this parasite in Southern Europe.

Status of wildlife health monitoring in the United Kingdom

There is a clear need to monitor the health of wildlife in the UK, to help to understand the population dynamics of endangered species and to detect any harm to the welfare of wild animals caused by human beings. Despite previous proposals, there has been little progress in the development of a national programme of monitoring. With notable exceptions, the current schemes for investigating the morbidity and mortality of wild animals cover only limited groups of animals and are fragmented and uncoordinated. They consist of statutory schemes of restricted scope, and studies in universities, institutes and wildlife rehabilitation centres with limited funding. As a result, significant disease incidents may remain undetected and others may not be investigated fully, posing risks to the welfare and conservation of wildlife, the welfare of domestic animals, and in some cases to human health. Coordinated national schemes for the surveillance of the health of wildlife are already established in France, the USA and Canada and their best characteristics could be used to develop a scheme for the UK.

Conditions in grey seal pups (Halichoerus grypus) presented for rehabilitation

A survey was carried out on the condition of 188 live grey seal (Halichoerus grypus) pups presented for rehabilitation from the coasts of south-west England between 1992 and 1998. The survey was carried out to assess the incidence of malnutrition, hyperthermia, respiratory and gastrointestinal conditions, and also the incidence of traumatic, skin, oral and ocular lesions. Malnutrition was a common finding in pups approaching weaning (mid-moult pups) and those at the point of weaning or postweaning (moulted pups) (62 per cent and 82 per cent, respectively). Separation from the dam, believed to be the main cause of malnutrition in grey seals, was encountered frequently in unweaned pups (91 per cent). Thirty-nine per cent of pups presented with a respiratory condition, 38 per cent with hyperthermia and 9 per cent with diarrhoea. Seven per cent and 14 per cent of pups had confirmed respiratory and gastrointestinal parasitic infestations respectively, although these were probably underestimates. Clinically significant traumatic lesions were seen in 41 per cent, oral ulceration in 26 per cent, ocular conditions in 13 per cent, nail bed infections in 13 per cent and oiling in 10 per cent of pups. Umbilical infections and other skin and oral conditions were also encountered. The incidence of these conditions is compared with data from dead grey seals, and clinical conditions in other pinniped species presented for rehabilitation.