Exposure of harbour seals Phoca vitulina to Brucella in declining populations across Scotland

A Review of Circumpolar Arctic Marine Mammal Health-A Call to Action in a Time of Rapid Environmental Change

The impacts of climate change on the health of marine mammals are increasingly being recognised. Given the rapid rate of environmental change in the Arctic, the potential ramifications on the health of marine mammals in this region are a particular concern. There are eleven endemic Arctic marine mammal species (AMMs) comprising three cetaceans, seven pinnipeds, and the polar bear (Ursus maritimus). All of these species are dependent on sea ice for survival, particularly those requiring ice for breeding. As air and water temperatures increase, additional species previously non-resident in Arctic waters are extending their ranges northward, leading to greater species overlaps and a concomitant increased risk of disease transmission. In this study, we review the literature documenting disease presence in Arctic marine mammals to understand the current causes of morbidity and mortality in these species and forecast future disease issues. Our review highlights potential pathogen occurrence in a changing Arctic environment, discussing surveillance methods for 35 specific pathogens, identifying risk factors associated with these diseases, as well as making recommendations for future monitoring for emerging pathogens. Several of the pathogens discussed have the potential to cause unusual mortality events in AMMs. Brucella, morbillivirus, influenza A virus, and Toxoplasma gondii are all of concern, particularly with the relative naivety of the immune systems of endemic Arctic species. There is a clear need for increased surveillance to understand baseline disease levels and address the gravity of the predicted impacts of climate change on marine mammal species.

Habitat and resource segregation of two sympatric seals in the North Sea

The study of ecological niche segregation in sympatric species is essential to understand ecosystem functioning and its response to potential changes. In the North Sea, sympatric grey and harbour seals may present competition for food resources sustained by intense fishing activities and recent increase of seal populations. In order to coexist and reduce inter-specific competition, sympatric species must segregate at least one aspect of their ecological niches: temporal, spatial or resource segregation. We aim to study the foraging resources and foraging distributions of grey seals and harbour seals and the potential competition between these species in the North Sea. Therefore, we analysed stable isotopic composition of C, N and S (δ¹³C, δ¹⁵N and δ³⁴S values), and the concentrations of Hg and Se in blood of harbour and grey seals from the North Sea. Blood samples were collected on 45 grey seals and 37 harbour seals sampled along German and Scottish coasts. Stable isotope ratios were performed with an isotope ratio mass spectrometer coupled to an N-C-S elemental analyser for automated analyses. Total mercury concentrations (T-Hg) were determined by atomic absorption spectroscopy and Se concentrations by ICP-MS. The multi-tracer approach shown spatial and resource partitioning within grey and harbour seal living along German and Scottish coasts. Data indicate 1) the offshore foraging distribution of grey seals as reflected by the lower δ¹⁵N values and T-Hg concentrations and higher Se concentrations and 2) the inshore foraging distribution of harbour seals because of higher δ¹⁵N values and T-Hg concentrations and lower Se concentrations. The SIAR mixing model revealed 3) a more selective diet of grey seals compared to harbour seals and 4) the importance of sandeels in grey seal diet reflected by their high δ³⁴S values. Lastly, diet ellipse overlaps between grey seals and harbour seals sampled along the German coasts suggested 5) a potential sharing of food resources, possibly due to the increase number of grey seals number in this area during the foraging season - all year except breeding and moulting periods. The multi-tracer approach of this study provides a more robust discrimination among diet resources and spatial foraging distributions of grey seals and harbour seals in the North Sea.

Serological screening for Brucella spp. and Leptospira spp. antibodies in southern elephant seals Mirounga leonina from Elephant Island, Antarctica, in 2003 and 2004

Brucella spp. and Leptospira spp. antibodies were surveyed in 35 southern elephant seals (SESs) Mirounga leonina at Elephant Island (South Shetland Islands), western Antarctic peninsula, in the Austral summer of 2003 and 2004. The rose Bengal test and a commercial competitive ELISA (c-ELISA) were used to detect Brucella spp. exposure, and the microscopic agglutination test (MAT) with 22 live serovars was used to determine anti-Leptospira spp. antibodies. We found evidence of Brucella spp. exposure in 3 of 35 (8.6%) SESs tested via the c-ELISA displaying high percentage inhibition (PI), similar to other studies in pinnipeds in which Brucella spp. antibodies have been determined. Two of the 3 positives were pups (PI = 70.4 and 86.6%), while the third was an adult female (PI = 48.8%). The 3 c-ELISA positive SESs were additionally tested via the serum agglutination test but were found to be negative. All individuals were negative for antibodies against 22 Leptospira spp. serovars by MAT. These results contribute to the knowledge and monitoring of zoonotic pathogens with epizootic potential in Southern Ocean pinnipeds. Given the potential impact that pathogens may have on the abundance of wild (sometimes threatened and endangered) populations, constant monitoring and surveillance are required to prevent pathogen spread, particularly under forecast climate change scenarios.

Perturbation drives changing metapopulation dynamics in a top marine predator

Metapopulation theory assumes a balance between local decays/extinctions and local growth/new colonisations. Here we investigate whether recent population declines across part of the UK harbour seal range represent normal metapopulation dynamics or are indicative of perturbations potentially threatening the metapopulation viability, using 20 years of population trends, location tracking data (n = 380), and UK-wide, multi-generational population genetic data (n = 269). First, we use microsatellite data to show that two genetic groups previously identified are distinct metapopulations: northern and southern. Then, we characterize the northern metapopulation dynamics in two different periods, before and after the start of regional declines (pre-/peri-perturbation). We identify source-sink dynamics across the northern metapopulation, with two putative source populations apparently supporting three likely sink populations, and a recent metapopulation-wide disruption of migration coincident with the perturbation. The northern metapopulation appears to be in decay, highlighting that changes in local populations can lead to radical alterations in the overall metapopulation's persistence and dynamics.

Comparative Ecology of Bartonella and Brucella Infections in Wild Carnivores

Phylogenetic sister clades Bartonella and Brucella within the order Rhizobiales present some common biological characteristics as well as evident differences in adaptations to their mammalian reservoirs. We reviewed published data on Bartonella and Brucella infections in wild carnivores to compare the ecology of these bacteria in relatively similar host environments. Arthropod vectors are the main mechanism for Bartonella species transmission between mammalian hosts. The role of arthropods in transmission of Brucella remains disputed, however experimental studies and reported detection of Brucella in arthropods indicate potential vector transmission. More commonly, transmission of Brucella occurs via contact exposure to infected animals or the environment contaminated with their discharges. Of 26 species of carnivores tested for both Bartonella and Brucella, 58% harbored either. Among them were bobcats, African lions, golden jackals, coyotes, wolves, foxes, striped skunks, sea otters, raccoons, and harbor seals. The most common species of Bartonella in wild carnivores was B. henselae, found in 23 species, followed by B. rochalimae in 12, B. clarridgeiae in ten, and B. vinsonii subsp. berkhoffii in seven. Among Brucella species, Br. abortus was reported in over 30 terrestrial carnivore species, followed by Br. canis in seven. Marine carnivores, such as seals and sea lions, can host Br. pinnipedialis. In contrast, there is no evidence of a Bartonella strain specific for marine mammals. Bartonella species are present practically in every sampled species of wild felids, but of 14 Brucella studies of felids, only five reported Brucella and those were limited to detection of antibodies. We found no reports of Bartonella in bears while Brucella was detected in these animals. There is evident host-specificity of Bartonella species in wild carnivores (e.g., B. henselae in felids and B. vinsonii subsp. berkhoffii in canids). A co-adaptation of Brucella with terrestrial wild carnivore hosts is not as straightforward as in domestic animals. Wild carnivores often carry the same pathogens as their domesticated relatives (cats and dogs), but the risk of exposure varies widely because of differences in biology, distribution, and historical interactions.

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.