Transmission of morbilliviruses within and among marine mammal species

California sea lion (Zalophus californianus) lymph-node explant reveals involvement and possible transcriptional regulation of SLAM and nectin-4 during phocine distemper virus infection

Phocine distemper virus (PDV) is a significant cause of mortality for phocid seals; however, the susceptibility of otariids to this virus is poorly understood. The authors used a lymph-node explant culture system from California sea lions (Zalophus californianus, CSL) to investigate: (1) the role of signaling lymphocyte activation molecule (SLAM) and nectin-4 in PDV infection and their cellular expression patterns, (2) if PDV induces transcriptional regulation of cell-entry receptors, and (3) the involvement of apoptosis in PDV infection. PDV replicated in the lymph-node explants with peak replication 3 days post-infection (dpi), but the replication was not sustained 4 to 5 dpi. The PDV+ cells co-localized SLAM and nectin-4. These cells expressed IBA1, indicating a histiocytic lineage. Comparison of receptor expression between infected and mock-infected lymph nodes suggested transcriptional downregulation of both receptors during the initial stage of infection and upregulation during the late stage of infection, but the values lack of statistical significance. Cleaved caspase-3+ cells were slightly increased in the infected lymph nodes compared with the mock-infected lymph node from 1 to 4 dpi, but without statistical significance, and a few apoptotic cells co-expressed PDV. The results suggest that lymph-node explants might be an important model to study PDV pathogenesis. CSLs have the potential to be infected with PDV, as they express both cell-entry receptors in histiocytes. The lack of statistical significance in the PDV replication, transcriptional regulation of viral receptors, and changes in apoptosis suggest that although CSL might be infected by PDV, they might be less susceptible than phocid species.

Epidemiological and genetic analysis of Cetacean Morbillivirus circulating on the Italian coast between 2018 and 2021

Cetacean morbillivirus (CeMV) has caused several outbreaks, unusual mortality events, and interepidemic single-lethal disease episodes in the Mediterranean Sea. Since 2012, a new strain with a northeast (NE) Atlantic origin has been circulating among Mediterranean cetaceans, causing numerous deaths. The objective of this study was to determine the prevalence of CeMV in cetaceans stranded in Italy between 2018 and 2021 and characterize the strain of CeMV circulating. Out of the 354 stranded cetaceans along the Italian coastlines, 113 were CeMV-positive. This prevalence (31.9%) is one of the highest reported without an associated outbreak. All marine sectors along the Italian coastlines, except for the northern Adriatic coast, reported a positive molecular diagnosis of CeMV. In one-third of the CeMV-positive cetaceans submitted to a histological evaluation, a chronic form of the infection (detectable viral antigen, the absence of associated lesions, and concomitant coinfections) was suspected. Tissues from 24 animals were used to characterize the strain, obtaining 57 sequences from phosphoprotein, nucleocapsid, and fusion protein genes, which were submitted to GenBank. Our sequences showed the highest identity with NE-Atlantic strain sequences, and in the phylogenetic study, they clustered together with them. Regarding age and species, most of these individuals were adults (17/24, 70.83%) and striped dolphins (19/24, 79.16%). This study improves our understanding on the NE-Atlantic CeMV strain in the Italian waters, supporting the hypothesis of an endemic circulation of the virus in this area; however, additional studies are necessary to deeply comprehend the epidemiology of this strain in the Mediterranean Sea.

Pathogen Exposure in White Whales (Delphinapterus leucas) in Svalbard, Norway

The Svalbard white whale (Delphinapterus leucas) population is one of the smallest in the world, making it particularly vulnerable to challenges such as climate change and pathogens. In this study, serum samples from live captured (2001−2016) white whales from this region were investigated for influenza A virus (IAV) antibodies (Abs) (n = 27) and RNA (n = 25); morbillivirus (MV) Abs (n = 3) and RNA (n = 25); Brucella spp. Abs; and Toxoplasma gondii Abs (n = 27). IAV Abs were found in a single adult male that was captured in Van Mijenfjorden in 2001, although no IAV RNA was detected. Brucella spp. Abs were found in 59% of the sample group (16/27). All MV and T. gondii results were negative. The results show that Svalbard white whales have been exposed to IAV and Brucella spp., although evidence of disease is lacking. However, dramatic changes in climate and marine ecosystems are taking place in the Arctic, so surveillance of health parameters, including pathogens, is critical for tracking changes in the status of this vulnerable population.

Cross-species recognition and molecular basis of SARS-CoV-2 and SARS-CoV binding to ACE2s of marine animals

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has an extremely broad host range that includes hippopotami, which are phylogenetically closely related to whales. The cellular ACE2 receptor is one of the key determinants of the host range. Here, we found that ACE2s from several marine mammals and hippopotami could efficiently bind to the receptor-binding domain (RBD) of both SARS-CoV and SARS-CoV-2 and facilitate the transduction of SARS-CoV and SARS-CoV-2 pseudoviruses into ACE2-expressing cells. We further resolved the cryo-electron microscopy complex structures of the minke whale ACE2 and sea lion ACE2, respectively, bound to the RBDs, revealing that they have similar binding modes to human ACE2 when it comes to the SARS-CoV-2 RBD and SARS-CoV RBD. Our results indicate that marine mammals could potentially be new victims or virus carriers of SARS-CoV-2, which deserves further careful investigation and study. It will provide an early warning for the prospective monitoring of marine mammals.

Sequence diversity and differences at the highly duplicated MHC-I gene reflect viral susceptibility in sympatric pinniped species

Differences in disease susceptibility among species can result from rapid host-pathogen coevolution and differences in host species ecology that affect the strength and direction of natural selection. Among two sympatric pinniped species that differ in sociality and putative disease exposure, we investigate observed differences in susceptibility through an analysis of a highly variable, duplicated gene family involved in the vertebrate immune response. Using high-throughput amplicon sequencing, we characterize diversity at the two exons that encode the peptide binding region of the major histocompatibility complex class I (MHC-I) gene in harbor (N = 60) and gray (N = 90) seal populations from the Northwest Atlantic. Across species, we identified 106 full-length exon 2 and 103 exon 3 sequence variants and a minimum of 11 duplicated MHC-I loci. The sequence variants clustered in 15 supertypes defined by the physiochemical properties of the peptide binding region, including a putatively novel Northwest Atlantic MHC-I diversity sublineage. Trans-species polymorphisms, dN/dS ratios, and evidence of gene conversion among supertypes are consistent with balancing selection acting on this gene. High functional redundancy suggests particularly strong selection among gray seals at the novel Northwest Atlantic MHC-I diversity sublineage. At exon 2, harbor seals had a significantly greater number of variants per individual than gray seals, but fewer supertypes. Supertype richness and private supertypes are hypothesized to contribute to observed differences in disease resistance between species, as consistently, across the North Atlantic and many disease outbreaks, gray seals appear to be more resistant to respiratory viruses than harbor seals.

Neuropathological Characterization of Dolphin Morbillivirus Infection in Cetaceans Stranded in Italy

Simple Summary

There is abundant literature reporting demyelination in dogs and pinnipeds affected by morbillivirus infection, but myelinopathy is poorly investigated in stranded cetaceans affected with the virus. Also, the neuropathogenesis of cetacean morbillivirus infection has not been fully clarified, leaving questions on cell tropism unanswered. A novel dolphin morbillivirus lineage of Atlantic origin circulating in Italian waters replaced the previous Mediterranean strain in late 2015; however, differences in virulence and pathogenesis between the two strains have not yet been documented. The aims of the present study were to: describe histopathological changes and immunohistochemical findings in the central nervous system of 31 cetaceans which tested positive on molecular investigations for the two dolphin morbillivirus strains; characterize by double indirect immunofluorescence staining the areas of myelin damage. The most frequently observed morbillivirus-associated lesions were astro-microgliosis, neuronal necrosis, spongiosis, malacia, and non-suppurative meningoencephalitis. Demyelination was detected by means of a specific myelin biomarker. Inside and around the demyelinated areas there were morbillivirus antigen-bearing cells of mainly neuronal and microglial origin, associated with marked astro and microglia reactivity. Molecular and immunohistochemical analysis suggested a higher neurotropic affinity of the novel circulating strain.

Abstract

Cetacean morbillivirus (CeMV) is responsible for epidemic and endemic fatalities in free-ranging cetaceans. Neuro-inflammation sustained by CeMV is a leading cause of death in stranded cetaceans. A novel dolphin morbillivirus (DMV) strain of Atlantic origin circulating in Italian waters since early 2016 has caused acute/subacute lesions associated with positive immunolabelling of the virus. To date, myelin damage has not been fully documented and investigated in cetaceans. This study describes neuropathological findings in the brain tissue of 31 cetaceans found stranded along the Italian coastline and positive for DMV infection on molecular testing. Cell changes in the areas of myelinopathy were revealed by double indirect immunofluorescence. The most frequent DMV-associated lesions were astro-microgliosis, neuronal necrosis, spongiosis, malacia, and non-suppurative meningoencephalitis. Myelin reduction and areas of demyelination were revealed by means of a specific myelin biomarker. Morbilliviral antigen immunolabelling was mainly observed in neurons and microglial cells, in association with a marked activation of microglia and astrocytes. These findings extend our knowledge of DMV-associated brain lesions and shed light on their pathogenesis.

Is a Little Enough? Paucity of Immune Proteins in Serum of Precocial Neonates of a Marine Carnivoran—the Atlantic Grey Seal

Mammalian mothers usually provide their offspring with large quantities of immunoglobulins (antibodies) for circulation in blood, either trans-placentally before birth, via colostrum briefly thereafter, or, less commonly, from milk. Neonates of true, phocid seals, however, are peculiarly impoverished in serum immunoglobulins, the levels of which slowly increase but do not reach adult levels by the time of weaning. We investigated whether grey seal (Halichoerus grypus) neonates compensate through an elevation or rapid maturation in levels of serum innate immune factors, namely acute phase and complement proteins. Instead, their sera contained remarkably low levels of acute phase proteins (including C-reactive protein, haptoglobin, hemopexin, ceruloplasmin, orosomucoid), compared to their mothers, that barely increased to adult levels by weaning. For complement, there was a strong demarcation between the early activation and amplification cascade components (present at normal adult levels in pups) and the late lytic membrane attack complex and regulatory proteins (consistently at low relative levels). Phocid neonates therefore differ dramatically from land Carnivorans, such as dogs and cats, in early life immune protection. That neonatal phocids survive this apparent vulnerability to infections between birth and weaning prompts questions as to what other mechanisms protect them, and the adaptive value of their seeming vulnerability.

Molecular signatures in cetacean morbillivirus and host species proteomes: Unveiling the evolutionary dynamics of an enigmatic pathogen?

Cetacean morbillivirus (CeMV) infects marine mammals often causing a fatal respiratory and neurological disease. Recently, CeMV has expanded its geographic and host species range, with cases being reported worldwide among dolphins, whales, seals, and other aquatic mammalian species, and therefore has emerged as the most threatening nonanthropogenic factor affecting marine mammal's health and conservation. Extensive research efforts have aimed to understand CeMV epidemiology and ecology, however, the molecular mechanisms underlying its transmission and pathogenesis are still poorly understood. In particular, the field suffers from a knowledge gap on the structural and functional properties of CeMV proteins and their host interactors. Nevertheless, the body of scientific literature produced in recent years has inaugurated new investigational trends, driving future directions in CeMV molecular research. In this mini-review, the most recent literature has been summarized in the context of such research trends, and categorized into four priority research topics, such as (1) the interaction between CeMV glycoprotein and its host cell receptors across several species; (2) the CeMV molecular determinants responsible for different disease phenotype; (3) the host molecular determinants responsible for differential susceptibility to CeMV infection; (4) the CeMV molecular determinants responsible for difference virulence among circulating CeMV strains. Arguably, these are the most urgent topics that need to be investigated and that most promisingly will help to shed light on the details of CeMV evolutionary dynamics in the immediate future.

Emergence and radiation of distemper viruses in terrestrial and marine mammals

Canine distemper virus (CDV) and phocine distemper virus (PDV) are major pathogens to terrestrial and marine mammals. Yet little is known about the timing and geographical origin of distemper viruses and to what extent it was influenced by environmental change and human activities. To address this, we (i) performed the first comprehensive time-calibrated phylogenetic analysis of the two distemper viruses, (ii) mapped distemper antibody and virus detection data from marine mammals collected between 1972 and 2018, and (iii) compiled historical reports on distemper dating back to the eighteenth century. We find that CDV and PDV diverged in the early seventeenth century. Modern CDV strains last shared a common ancestor in the nineteenth century with a marked radiation during the 1930s-1950s. Modern PDV strains are of more recent origin, diverging in the 1970s-1980s. Based on the compiled information on distemper distribution, the diverse host range of CDV and basal phylogenetic placement of terrestrial morbilliviruses, we hypothesize a terrestrial CDV-like ancestor giving rise to PDV in the North Atlantic. Moreover, given the estimated timing of distemper origin and radiation, we hypothesize a prominent role of environmental change such as the Little Ice Age, and human activities like globalization and war in distemper virus evolution.

Cryo-EM structure of the cetacean morbillivirus nucleoprotein-RNA complex

Cetacean morbillivirus (CeMV) is an emerging and highly infectious paramyxovirus that causes outbreaks in cetaceans and occasionally in pinnipeds, representing a major threat to biodiversity and conservation of endangered marine mammal populations in both hemispheres. As for all non-segmented, negative-sense, single-stranded RNA (ssRNA) viruses, the morbilliviral genome is enwrapped by thousands of nucleoprotein (N) protomers. Each bound to six ribonucleotides, N protomers assemble to form a helical ribonucleoprotein (RNP) complex that serves as scaffold for nucleocapsid formation and as template for viral replication and transcription. While the molecular details on RNP complexes elucidated in human measles virus (MeV) served as paradigm model for these processes in all members of the Morbillivirus genus, no structural information has been obtained from other morbilliviruses, nor has any CeMV structure been solved so far. We report the structure of the CeMV RNP complex, reconstituted in vitro upon binding of recombinant CeMV N to poly-adenine ssRNA hexamers and solved to 4.0 Å resolution by cryo-electron microscopy. In spite of the amino acid sequence similarity and consequently similar folding of the N protomer, the CeMV RNP complex exhibits different helical parameters as compared to previously reported MeV orthologs. The CeMV structure reveals exclusive interactions leading to more extensive protomer-RNA and protomer-protomer interfaces. We identified twelve residues, among those varying between CeMV strains, as putatively important for the stabilization of the RNP complex, which highlights the need to study the potential of CeMV N mutations that modulate nucleocapsid assembly to also affect viral phenotype and host adaptation.

Linking morbillivirus exposure to individual habitat use of common bottlenose dolphins (Tursiops truncatus) between geographically different sites

Dolphin morbillivirus (DMV) is a virulent pathogen that causes high mortality outbreaks in delphinids globally and is spread via contact among individuals. Broadly ranging nearshore and open-ocean delphinids are likely reservoir populations that transmit DMV to estuarine populations. We assessed the seroprevalence of DMV antibodies and determined the habitat use of common bottlenose dolphins, Tursiops truncatus truncatus, from two estuarine sites, Barataria Bay and Mississippi Sound, in the northern Gulf of Mexico. We predicted that risk to DMV exposure in estuarine dolphins is driven by spatial overlap in habitat use with reservoir populations. Serum was collected from live-captured dolphins and tested for DMV antibodies. Habitat use of sampled individuals was determined by analysing satellite-tracked movements and stable isotope values. DMV seroprevalences were high among dolphins at Barataria Bay (37%) and Mississippi Sound (44%), but varied differently within sites. Ranging patterns of Barataria Bay dolphins were categorized into two groups: Interior and Island-associated. DMV seroprevalences were absent in Interior dolphins (0%) but high in Island-associated dolphins (45%). Ranging patterns of Mississippi Sound dolphins were categorized into three groups: Interior, Island-east and Island-west. DMV seroprevalences were detected across Mississippi Sound (Interior: 60%; Island-east: 20%; and Island-west: 43%). At both sites, dolphins in habitats with greater marine influence had enriched δ¹³ C values, and Barataria Bay dolphins with positive DMV titres had carbon isotope values indicative of marine habitats. Positive titres for DMV antibodies were more common in the lower versus upper parts of Barataria Bay but evenly distributed across Mississippi Sound. A dolphin's risk of exposure to DMV is influenced by how individual ranging patterns interact with environmental geography. Barataria Bay's partially enclosed geography likely limits the nearshore or open-ocean delphinids that carry DMV from interacting with dolphins that use interior, estuarine habitats, decreasing their exposure to DMV. Mississippi Sound's relatively open geography allows for greater spatial overlap and mixing among estuarine, nearshore and/or open-ocean cetaceans. The spread of DMV, and likely other diseases, is affected by the combination of individual movements, habitat use and the environment.

A comparative phylogenomic analysis of SARS-CoV-2 strains reported from non-human mammalian species and environmental samples

Coronaviruses (CoVs) infect a wide range of domestic and wild mammals. These viruses have a potential and tendency to cross-species barriers and infect humans. Novel human coronavirus 2019-nCoV (hCoV-19) emerged from Wuhan, China, and has caused a global pandemic. Genomic features of SARS-CoV-2 may attribute inter-species transmission and adaptation to a novel host, and therefore is imperative to explicate the evolutionary dynamics of the viral genome and its propensity for differential host selection. We conducted an in silico analysis of all the coding gene sequences of SARS-CoV-2 strains (n = 39) originating from a range of non-human mammalian species, including pangolin, bat, dog, cat, tiger, mink, mouse, and the environmental samples such as wastewater, air and surface samples from the door handle and seafood market. Compared to the reference SARS-CoV-2 strain (MN908947; Wuhan-Hu-1), phylogenetic and comparative residue analysis revealed the circulation of three variants, including hCoV-19 virus from humans and two hCoV-19-related precursors from bats and pangolins. A lack of obvious differences as well as a maximum genetic homology among dog-, cat-, tiger-, mink-, mouse-, bat- and pangolin-derived SARS-CoV-2 sequences suggested a likely evolution of these strains from a common ancestor. Several residue substitutions were observed in the receptor-binding domain (RBD) of the spike protein, concluding a promiscuous nature of the virus for host species where genomic alternations may be required for the adaptation to novel host/s. However, such speculation needs in vitro investigations to unleash the influence of substitutions towards species-jump and disease pathogenesis.

Phocine distemper virus uses phocine and other animal SLAMs as a receptor but not human SLAM

Morbilliviruses use the signaling lymphocyte activation molecule (SLAM) as a receptor to infect their hosts. Seals are almost the only animal species that show apparent infection with phocine distemper virus (PDV). Seal SLAM functioned as a PDV receptor. However, dolphin- and dog-SLAM molecules, but not human SLAM, were also fully functional PDV receptors. These data suggest that the host range of PDV is not simply determined by its SLAM usage. However, human nonsusceptibility to PDV infection may be at least partly attributable to the inability of PDV to use human SLAM as a receptor.

Pastoral production is associated with increased peste des petits ruminants seroprevalence in northern Tanzania across sheep, goats and cattle

Peste des petits ruminants virus (PPRV) causes a contagious disease of high morbidity and mortality in small ruminant populations globally. Using cross-sectional serosurvey data collected in 2016, our study investigated PPRV seroprevalence and risk factors among sheep, goats and cattle in 20 agropastoral (AP) and pastoral (P) villages in northern Tanzania. Overall observed seroprevalence was 21.1% (95% exact confidence interval (CI) 20.1-22.0) with 5.8% seroprevalence among agropastoral (95% CI 5.0-6.7) and 30.7% among pastoral villages (95% CI 29.3-32.0). Seropositivity varied significantly by management (production) system. Our study applied the catalytic framework to estimate the force of infection. The associated reproductive numbers (R0) were estimated at 1.36 (95% CI 1.32-1.39), 1.40 (95% CI 1.37-1.44) and 1.13 (95% CI 1.11-1.14) for sheep, goats and cattle, respectively. For sheep and goats, these R0 values are likely underestimates due to infection-associated mortality. Spatial heterogeneity in risk among pairs of species across 20 villages was significantly positively correlated (R2: 0.59-0.69), suggesting either cross-species transmission or common, external risk factors affecting all species. The non-negligible seroconversion in cattle may represent spillover or cattle-to-cattle transmission and must be investigated further to understand the role of cattle in PPRV transmission ahead of upcoming eradication efforts.

A review of pathogens in selected Baltic Sea indicator species

Here we review the state-of-the-art of pathogens in select marine and terrestrial key species of the Baltic Sea, i.e. ringed seal (Pusa hispida), harbour seal (Phoca vitulina), grey seal (Halichoerus grypus), harbour porpoise (Phocoena phocoena), common eider (Somateria mollissima), pink-footed goose (Anser brachyrhynchus) and white-tailed eagle (Haliaeetus albicilla). This review is the first to merge and present available information and baseline data for the FP7 BONUS BaltHealth project: Baltic Sea multilevel health impacts on key species of anthropogenic hazardous substances. Understanding the spread, prevalence and effects of wildlife pathogens is important for the understanding of animal and ecosystem health, ecosystem function and services, as well as human exposure to zoonotic diseases. This review summarises the occurrence of parasites, viruses and bacteria over the past six decades, including severe outbreaks of Phocine Distemper Virus (PDV), the seroprevalence of Influenza A and the recent increase in seal parasites. We show that Baltic high trophic key species are exposed to multiple bacterial, viral and parasitic diseases. Parasites, such as C. semerme and P. truncatum present in the colon and liver Baltic grey seals, respectively, and anisakid nematodes require particular monitoring due to their effects on animal health. In addition, distribution of existing viral and bacterial pathogens, along with the emergence and spread of new pathogens, need to be monitored in order to assess the health status of key Baltic species. Relevant bacteria are Streptococcus spp., Brucella spp., Erysipelothrix rhusiopathiae, Mycoplasma spp. and Leptospira interrogans; relevant viruses are influenza virus, distemper virus, pox virus and herpes virus. This is of special importance as some of the occurring pathogens are zoonotic and thus also pose a potential risk for human health. Marine mammal handlers, as well as civilians that by chance encounter marine mammals, need to be aware of this risk. It is therefore important to continue the monitoring of diseases affecting key Baltic species in order to assess their relationship to population dynamics and their potential threat to humans. These infectious agents are valuable indicators of host ecology and can act as bioindicators of distribution, migration, diet and behaviour of marine mammals and birds, as well as of climate change and changes in food web dynamics. In addition, infectious diseases are linked to pollutant exposure, overexploitation, immune suppression and subsequent inflammatory disease. Ultimately, these diseases affect the health of the entire ecosystem and, consequently, ecosystem function and services. As global warming is continuously increasing, the impact of global change on infectious disease patterns is important to monitor in Baltic key species in the future.

Camelids and Cattle Are Dead-End Hosts for Peste-des-Petits-Ruminants Virus

Peste-des-petits-ruminants virus (PPRV) causes a severe respiratory disease in small ruminants. The possible impact of different atypical host species in the spread and planed worldwide eradication of PPRV remains to be clarified. Recent transmission trials with the virulent PPRV lineage IV (LIV)-strain Kurdistan/2011 revealed that pigs and wild boar are possible sources of PPRV-infection. We therefore investigated the role of cattle, llamas, alpacas, and dromedary camels in transmission trials using the Kurdistan/2011 strain for intranasal infection and integrated a literature review for a proper evaluation of their host traits and role in PPRV-transmission. Cattle and camelids developed no clinical signs, no viremia, shed no or only low PPRV-RNA loads in swab samples and did not transmit any PPRV to the contact animals. The distribution of PPRV-RNA or antigen in lymphoid organs was similar in cattle and camelids although generally lower compared to suids and small ruminants. In the typical small ruminant hosts, the tissue tropism, pathogenesis and disease expression after PPRV-infection is associated with infection of immune and epithelial cells via SLAM and nectin-4 receptors, respectively. We therefore suggest a different pathogenesis in cattle and camelids and both as dead-end hosts for PPRV.

Dolphin Morbillivirus in Eurasian Otters, Italy

We report biomolecular evidence of dolphin morbillivirus in 4 wild Eurasian otters (Lutra lutra) from southern Italy; 2 animals showed simultaneous immunohistochemical reactivity against morbilliviral antigen. These cases add further concern and support to the progressively expanding host range of dolphin morbillivirus in the western Mediterranean Sea.

A comparative phylogenomic analysis of peste des petits ruminants virus isolated from wild and unusual hosts

Peste des petits ruminants virus (PPRV) infects a wide range of domestic and wild ruminants, and occasionally unusual hosts such as camel, cattle and pig. Given their broad host-spectrum and disease endemicity in several developing countries, it is imperative to elucidate the viral evolutionary insights for their dynamic pathobiology and differential host-selection. For this purpose, a dataset of all available (n = 37) PPRV sequences originating from wild and unusual hosts was composed and in silico analysed. Compared to domestic small ruminant strains of same geographical region, phylogenomic and residue analysis of PPRV sequences originating from wild and unusual hosts revealed a close relationship between strains. A lack of obvious difference among the studied sequences and deduced residues suggests that these are the host factors that may play a role in their susceptibility to PPRV infection, immune response, pathogenesis, excretion patterns and potential clinical signs or resistance to clinical disease. Summarizing together, the comparative analysis enhances our understanding towards molecular epidemiology of the PPRV in wild and unusual hosts for appropriate intervention strategies particularly at livestock-wildlife interface.

Circulation of a novel strain of dolphin morbillivirus (DMV) in stranded cetaceans in the Mediterranean Sea

Dolphin morbillivirus (DMV) has been responsible for several outbreaks of systemic infection and has resulted in cetacean strandings in the Mediterranean. In August-October 2016, seven striped dolphins (Stenella coeruleoalba) stranded on the Sicilian coastline (Italy) tested positive for DMV. Tissue samples from brain, lung, pulmonary lymph nodes, heart, spleen, liver, stomach, intestine, kidneys and urinary bladder, as well as blowhole swabs, were collected during necropsy for molecular diagnostics and pathology studies. Extracted tissue RNA was screened for DMV by real-time reverse transcription polymerase chain reaction (PCR). Some tissues exhibited microscopic lesions that were consistent with DMV infection on histopathological and immunohistochemical grounds. Conventional reverse transcription PCR to target partial nucleoprotein and phosphoprotein genes yielded sequences used to genetically characterize the associated DMV strain. DMV RNA was detected by both PCR assays in all tested tissues of the seven dolphins, which suggests systemic infections, but was absent from another dolphin stranded on the Sicilian coastline during the same period. The partial phosphoprotein and nucleoprotein gene sequences from the positive dolphins were 99.7% and 99.5% identical, respectively, to the DMV sequences recently observed in cetaceans stranded on the Spanish Mediterranean. Our study suggests that this DMV strain is circulating in the Mediterranean.

New world origin of canine distemper: Interdisciplinary insights

OBJECTIVE

Canine distemper virus (CDV), human measles virus (HMV), and rinderpest virus (RPV) of cattle are morbilliviruses that have caused devastating outbreaks for centuries. This paper seeks to reconstruct the evolutionary history of CDV.

MATERIALS AND METHODS

An interdisciplinary approach is adopted, synthesizing paleopathological analysis of 96 Pre-Columbian dogs (750-1470 CE) from the Weyanoke Old Town, Virginia site, with historical reports, molecular analysis and morbilliviral epidemiology.

RESULTS

Both measles (c.900CE) and rinderpest (c. 376 BCE) were first reported in Eurasia, while canine distemper was initially described in South America much later (1735 CE); there are no paleopathological indications of CDV in Weyanoke Old Town dogs. Molecularly, CDV is closely related to HMV, while viral codon usage indicates CDV may have previously infected humans; South American measles epidemics occurred prior to the emergence of canine distemper and would have facilitated HMV transmission and adaptation to dogs.

CONCLUSIONS

The measles epidemics that decimated indigenous South American populations in the 1500-1700 s likely facilitated the establishment of CDV as a canine pathogen, which eventually spread to Europe and beyond.

SIGNIFICANCE

Understanding the historical and environmental conditions that have driven morbilliviral evolution provides important insights into potential future threats of animal/human cross-species infections.

LIMITATIONS

Interpreting historical disease descriptions is difficult and the archaeological specimens are limited. Molecular sequence data and codon usage analyses rely on modern viruses.

SUGGESTIONS FOR FURTHER RESEARCH

Interdisciplinary approaches are increasingly needed to understand diseases of the past and present, as critical information and knowledge is scattered in different disciplines.

Phylogenomic insights to the origin and spread of phocine distemper virus in European harbour seals in 1988 and 2002

The 1988 and 2002 phocine distemper virus (PDV) outbreaks in European harbour seals Phoca vitulina are among the largest mass mortality events recorded in marine mammals. Despite its large impact on harbour seal population numbers, and 3 decades of studies, many questions regarding the spread and temporal origin of PDV remain unanswered. Here, we sequenced and analysed 7123 bp of the PDV genome, including the coding and non-coding regions of the entire P, M, F and H genes in tissues from 44 harbour seals to shed new light on the origin and spread of PDV in 1988 and 2002. The phylogenetic analyses trace the origin of the PDV strain causing the 1988 outbreak to between May 1987 and April 1988, while the origin of the strain causing the 2002 outbreak can be traced back to between June 2001 and May 2002. The analyses further point to several independent introductions of PDV in 1988, possibly linked to a southward mass immigration of harp seals in the winter and spring of 1987-1988. The vector for the 2002 outbreak is unknown, but the epidemiological analyses suggest the subsequent spread of PDV from the epicentre in the Kattegat, Denmark, to haul-out sites in the North Sea through several independent introductions.

Dental anomalies and lesions in Eastern Atlantic harbor seals, Phoca vitulina vitulina (Carnivora, Phocidae), from the German North Sea

Skulls of 1,901 Eastern Atlantic harbor seals (Phoca vitulina vitulina) were systematically studied for externally visible dental anomalies and lesions. The sample comprised 927 males and 974 female individuals, with age at death ranging between 1 week and 25 years. Most of the skulls originated from animals collected in 1988, when the population suffered from a mass mortality event caused by the phocine distemper virus (PDV). Mean age (± SD) of females (6.7 ± 6.4 years) was higher (p = 0.002) than that of males (5.9 ± 5.2 years). In 264 individuals, one or more teeth were missing either congenitally (n = 26 animals, 1.4%) or due to intravital loss (n = 238 animals, 12.5%). One male exhibited congenital absence of all teeth (anodontia). As this animal had been reported to be almost hairless, the condition was tentatively diagnosed as a case of hypohidrotic ectodermal dysplasia. Males were more frequently (p = 0.002) affected by intravital tooth loss (15.0%) than females (10.2%). Supernumerary teeth were found in 3.4% of the skulls, with females (4.7%) showing hyperodontia more frequently (p < 0.001) than males (1.9%). Fifty-nine individuals (3.1%; 28 males, 31 females, p = 0.84) exhibited abnormal tooth morphology. Tooth fractures were noted in 40 seals (2.1%), with males being more frequently affected than females (p = 0.017). Periapical lesions were diagnosed in 143 skulls, with a tendency (p = 0.05) for males (8.7%) to be more frequently affected than females (6.4%). Enamel hypoplasia was not observed in the study sample. Analyzing the occurrence of dental anomalies and lesions in wild mammals can substantially contribute to an assessment of population health and thereby broaden the basis for effective species conservation and informed management decisions.