Phocine distemper virus: characterization of the morbillivirus causing the seal epizootic in northwestern Europe in 2002

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.

Complete Sequence and Annotation of the Mycoplasma phocirhinis Strain 852T Genome

The genome of Mycoplasma phocirhinis strain 852^T was examined for determinants of tropism or virulence. It encodes multiple orthologs of an immunosuppressor that may predispose susceptibility to infection or influence outcomes of intercurrent diseases in marine mammals.

The genome of Mycoplasma phocirhinis strain 852^T was examined for determinants of tropism or virulence. It encodes multiple orthologs of an immunosuppressor that may predispose susceptibility to infection or influence outcomes of intercurrent diseases in marine mammals.

Complete Sequence and Annotation of the Mycoplasma phocidae Strain 105T Genome

The genome of Mycoplasma phocidae strain 105^T was analyzed in order to improve our understanding of its role in epidemic marine mammal mortalities. It was found to encode a suite of immunosuppressors that may enable evasion of host defenses and modulate susceptibility to viral coinfections or their severity in seals.

Variable transcription of pro- and anti-inflammatory cytokines in phocine lymphocytes following canine distemper virus infection

Canine distemper virus (CDV) is a highly contagious viral pathogen. Domesticated dogs are the main reservoir of CDV. Although phocine distemper virus was responsible for the recent epidemics in seals in the North and Baltic Seas, most devastating epidemics in seals were also caused by CDV. To further study the pathogenesis of CDV infection in seals, it was the aim of the present study to investigate the mechanisms of CDV induced immunosuppression in seals by analyzing the gene transcription of different pro- and anti-inflammatory cytokines in Concanavalin A (Con A) stimulated and non-stimulated phocine lymphocytes in vitro following infection with the CDV Onderstepoort (CDV-OND) strain. Phocine lymphocytes were isolated via density gradient centrifugation. The addition of 1 μg/ml Con A and virus was either performed simultaneously or lymphocytes were stimulated for 48 h with Con A prior to virus infection. Gene transcription of interleukin (IL)-6, IL-12 and tumor necrosis factor alpha (TNFα) as pro-inflammatory cytokines and IL-4, IL-10 and transforming growth factor beta (TGFβ) as anti-inflammatory cytokines were determined by using RT-qPCR. CDV-OND infection caused an initial increase of pro-inflammatory phocine cytokines mRNA 24h after infection, followed by a decrease in gene transcription after 48 h. A strong increase in the transcription of IL-4 and TGFβ was detected after 48 h when virus and mitogen were added simultaneously. An increased IL-10 production occurred only when stimulation and infection were performed simultaneously. Furthermore, an inhibition of IL-12 on IL-4 was noticed in phocine lymphocytes which were stimulated for 48 h prior to infection. In summary, the duration of the stimulation or the lymphocytes seem to have an important influence on the cytokine transcription and indicates that the outcome of CDV infection is dependent on various factors that might sensitize lymphocytes or make them more susceptible or reactive to CDV infection.

Phocine distemper virus in seals, east coast, United States, 2006

: Phocine Distemper Virus in Seals

In 2006 and 2007, elevated numbers of deaths among seals, constituting an unusual mortality event, occurred off the coasts of Maine and Massachusetts, United States. We isolated a virus from seal tissue and confirmed it as phocine distemper virus (PDV). We compared the viral hemagglutinin, phosphoprotein, and fusion (F) and matrix (M) protein gene sequences with those of viruses from the 1988 and 2002 PDV epizootics. The virus showed highest similarity with a PDV 1988 Netherlands virus, which raises the possibility that the 2006 isolate from the United States might have emerged independently from 2002 PDVs and that multiple lineages of PDV might be circulating among enzootically infected North American seals. Evidence from comparison of sequences derived from different tissues suggested that mutations in the F and M genes occur in brain tissue that are not present in lung, liver, or blood, which suggests virus persistence in the central nervous system.