In the summer of 2000, proliferative lesions of the skin and oral mucosa were observed in 26 young harbor seals (Phoca vitulina) from a rehabilitation center in Schleswig-Holstein, Germany. Verrucose, roundish nodules, approximately 1-2 cm in diameter, were presented in the oral cavity, especially on the tongue. Some animals developed similarly sized spherical dermal elevations with ulceration on flippers, chest, neck, and perineum. Necropsy of one animal showed multifocal, verrucose nodules in the oral cavity and a mild tonsillitis. Histologically, the nodules were characterized by ballooning degeneration of the outer parts of the spiny layer and stratum granulosum, with large eosinophilic cytoplasmic inclusions and a perivascular to interstitial lymphohistiocytic infiltration accompanied by fibroblastic proliferation and neovascularization. Negative staining of mucosal tissue homogenates demonstrated parapoxvirus-like particles. The presence of parapoxvirus was confirmed by polymerase chain reaction, using primers specific for parapoxvirus of ungulates. By in situ hybridization, using a parapox-specific, digoxigenin-labeled DNA probe, abundant parapoxvirus DNA-positive epithelial cells were detected in the stratum granulosum and the outer parts of the spiny layer. There was no parapoxvirus-positive signal in the adjacent submucosa. Although DNA analysis revealed that the causative agent can clearly be distinct from terrestrial parapoxviruses, lesions resembled parapoxvirus infections in other terrestrial species, and the pattern of virus DNA distribution indicated a direct effect of the virus on keratinocytes. In contrast, changes in the corium may be considered an indirect response mediated by the virus or the immune system.

and IL-12 were found at admission, consistent with an activated immune system, whereas the anti-inflammatory cytokine IL-4 was increased before release, suggesting recovery from infections and a mature immune system. This study indicates that cytokines detection is highly sensitive for the status of the immune system of harbor seals.

The cellular immunity of newborn harbor seals and the influence of pollutants are rarely investigated. This study evaluated the lymphocyte proliferation using a lymphocyte proliferation test (LTT) to understand the dynamics of immune response in seal pups of varying ages from the moment they arrived in a seal center after active beaching until their release into wildlife 3 months later after rehabilitation. Moreover, the effect of various metals (Ag, Al, Au, Be, Cd, Co, Cr, Cu, different Hg compounds, Mo, Ni, Pb, Pd, Pt, Sn, Ti) on lymphocyte proliferation in terms of immunosuppression and hypersensitivity was investigated. First, a strong lymphocyte proliferation in newborns as a reflection of relative immunocompetence was found. Second, different metal-induced influences on lymphocyte proliferation such as specific inhibition by Be, Cd, Hg, and Sn as well as stimulation induced by Mo and Ni were determined. For seals tested repeatedly, the suppressive effect was detected in newborns but not found in the same animals when they were older and had become immunologically competent. Summarizing, the lymphocyte proliferation used as a marker in this investigation provided useful immunological information on these developing animals, and its application for toxicological studies on pollutants can be recommended.

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BackgroundFacing numerous challenges, such as illness, storms or human disturbance, some harbor seal (Phoca vitulina) pups lose contact to their dams and are found abandoned along the North Sea coast. In Schleswig-Holstein, pups with the prospect of surviving rehabilitation are admitted to the Seal Center Friedrichskoog. Despite elaborate clinical health assessments on admission, including differential hematology, in 2010, 17% of 108 admitted pups did not survive the first 20 days. The death rate during the years 2006 and 2009 varied between 9 and 19%. To broaden the spectrum of variables which could be predictive for survival, blood gas and serum analyses were performed for 99 pups using venous blood. Variables included total CO2, pH, partial CO2, HCO3–, base excess and anion gap as well as glucose, urea nitrogen, sodium, potassium and chloride. Moreover, total serum protein and fat (triglyceride) concentrations were measured for all pups on admission.ResultsRepeated measurements of 12 randomly selected individuals revealed a significant (p = 0.002) positive influence of time in rehabilitation on triglyceride concentrations. This trend probably shows the improvement of the pups’ nutritional status as a consequence of the shift from milk replacer formula to fish. No such positive influence was detected for total protein concentrations though. Hematologic values, including blood gases, were not predictive for survival.ConclusionsFor the first time blood gas values are reported in this study for a large sample size (N = 99) of seal pups (regardless of their health status). The ranges and medians calculated from the data can serve as a stepping stone towards the establishment of reference values for neonate harbor seals. However, future investigations on the development of blood gases in harbor seals with different health conditions and ages over time are necessary to allow for a better understanding of acid–base regulation in harbor seals.

This study on harbor seal (Phoca vitulina) pups of the North Sea evaluated concentrations of 14 essential and non-essential elements (Al, As, Be, Ca, Cd, Cr, Fe, Mn, Mo, Ni, Pb, Se, Sn, and Zn) in whole blood samples. The essential elements are analyzed to give references for health status determinations of pups. The measurement of classic toxic metals, like Pb or Cd, and other elements that may be in toxic concentrations in blood, is important due to their influence on health, particularly on the immune system. Blood samples of six seal pups found on the German Wadden Sea coast of Schleswig-Holstein in 2004 and transported to the Seal Centre Friedrichskoog, Germany were collected. The blood sampling was performed three times, immediately after collection of the newborns, after 1.5 months, and after 2 months before their release back into the wild. Inductively coupled plasma mass spectrometry and total reflection X-ray fluorescence spectrometry were used to determine the element concentrations. We found higher concentrations of Al, As, Fe, Mo, and Zn in blood samples of newborns compared to samples collected later, probably due to transplacental and lactational transfer from mother to fetus. Furthermore, there is a high need for, in particular, Fe and Zn in the developing organism, which may cause reduced values after some month. In contrast, the concentrations of Be, Cd, Ca, Cr, Pb, Mn, Ni, Se, and Sn, which were low in newborns and increased during the study, may be due to the fish fed to infant pups. Compared to free-ranging adults, in pups, the concentrations of Al, Ni, and Pb were higher in contrast to lower concentrations of As, Mn, and Mo. This case study is the first report on element levels in harbor seal pups of the North Sea.

Grey seals have become an important part of the ecosystem in the southern North Sea over the last 50 years. However, little is known about their spatial utilization of the German North Sea, especially in relation to the dispersal and behaviour of grey seal pups after weaning. We investigated these little-known aspects by recording the movements of 11 grey seal pups born at the largest German colony for 1–9 months after leaving the colony between 2015 and 2017. The individuals moved widely throughout the southern North Sea, including some individuals that moved far along the Danish coast or to Dutch and UK waters. A point process modelling approach revealed that pups increased their distance to Helgoland during the first 70 d at sea. The frequency of inferred foraging behaviour increased until week 7 and decreased afterwards, whereas fast travelling behaviour increased throughout the whole study period. These findings reflect the transition from naive to more experienced pups, with gradual increases in foraging effort, range and efficiency to account for their increasing energy demands for survival and growth. This study provides the first characterization of the dispersal, behaviour, and spatial utilization of recently weaned grey seal pups in the southern North Sea, which profoundly extents our knowledge of an increasingly important top predator in that area.

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