Porpoise Morbillivirus Research Articles

Novel cetacean morbillivirus in a rare Fraser\u2019s dolphin (Lagenodelphis hosei) stranding from Maui, Hawai\u2018i

Cetacean morbillivirus (CeMV) is a global threat to cetaceans. We report a novel morbillivirus from a Fraser’s dolphin (Lagenodelphis hosei) that stranded in Maui, Hawaii in 2018 that is dissimilar to the beaked whale morbillivirus previously identified from Hawaii and to other CeMV strains. Histopathological findings included intranuclear inclusions in bile duct epithelium, lymphoid depletion, rare syncytial cells and non-suppurative meningitis. Cerebellum and lung tissue homogenates were inoculated onto Vero.DogSLAMtag cells for virus isolation and cytopathic effects were observed, resulting in the formation of multinucleated giant cells (i.e., syncytia). Transmission electron microscopy of infected cell cultures also revealed syncytial cells with intracytoplasmic and intranuclear inclusions of viral nucleocapsids, consistent with the ultrastructure of a morbillivirus. Samples of the cerebellum, lung, liver, spleen and lymph nodes were positive for morbillivirus using a reverse transcription-polymerase chain reaction. The resulting 559 bp L gene sequence had the highest nucleotide identity (77.3%) to porpoise morbillivirus from Northern Ireland and the Netherlands. The resulting 248 bp P gene had the highest nucleotide identity to porpoise morbillivirus in Northern Ireland and the Netherlands and to a stranded Guiana dolphin (Sotalia guianensis) in Brazil (66.9%). As Fraser’s dolphins are a pelagic species that infrequently strand, a novel strain of CeMV may be circulating in the central Pacific that could have additional population impacts through transmission to other small island-associated cetacean species.

INFECTIOUS DISEASE AND TOXICOLOGICAL MONITORING OF STRANDED PACIFIC HARBOR SEALS (PHOCA VITULINA RICHARDSI) IN COOK INLET AS SURROGATES FOR MONITORING ENDANGERED BELUGAS (DELPHINAPTERUS LEUCAS).

Pacific harbor seals ( Phoca vitulina richardsi) and belugas ( Delphinapterus leucas ) eat many of the same prey species, occupy the same geographic area, and demonstrate site fidelity in Cook Inlet, Alaska. Although most direct research involving the critically endangered belugas is currently prohibited, studying harbor seals may provide important information about this beluga population. In recent years, harbor seal populations in Alaska have declined for unknown reasons. As part of its stranding program, the Alaska SeaLife Center (ASLC) managed 59 cases of live and dead stranded harbor seals from Cook Inlet between 1997 and 2011. Animals were screened for a variety of diseases and contaminants of concern. Animals were negative by serology to the following diseases: avian influenza, canine distemper virus, dolphin morbillivirus, porpoise morbillivirus, Leptospira canicola, L. grippotyphosa, L. pomona, Neospora caninum , Sarcocystis neurona , and Toxoplasma gondii . Positive titers were found against Brucella spp., phocine distemper virus, seal herpesvirus-1, L. bratislava, L. hardjo, and L. icterohemorrhagiae. All titers were stable or declining except in one animal with an increasing titer for seal herpesvirus-1. Fecal pathogen screenings identified normal flora as well as stable or declining low levels of potentially pathogenic and opportunistic bacteria, though most were of little concern for seal health. In most animals, toxicology screening showed that the majority of tested contaminants were below detectable limits. The level of evidence of exposure to pathogens of concern was low in harbor seals. Although the infectious disease burden and contaminant levels in belugas in Cook Inlet cannot be definitively determined without direct testing, pathogen and contaminant exposure is expected to be similar to that found in harbor seals in this region, as the harbor seals and belugas share the habitat and food resources.

Morbillivirus and Pilot Whale Deaths, Canary Islands, Spain, 2015

Morbillivirus and Pilot Whale Deaths, Canary Islands, Spain, 2015

Initial characterization of novel beaked whale morbillivirus in Hawaiian cetaceans.

Cetacean morbillivirus (CeMV) is a causative factor in epizootics that have resulted in thousands of deaths throughout the Atlantic and Mediterranean since 1987, but less is known of its presence and significance in the Pacific. The first case of CeMV reported in Hawai'i was in a Longman's beaked whale that stranded in 2010. The initial CeMV sequence from this individual indicated the possibility of a novel strain. To address this, archived samples from cetaceans that stranded in Hawai'i between 1997 and 2014 were screened for CeMV. The beaked whale morbillivirus (BWMV) was detected in 15 individuals representing 12 different species (24% of Code 1 and 2 stranded cetaceans). The earliest detected case was a humpback whale that stranded in 1998. Sequence comparisons of a 2.2 kb sequence spanning the phosphoprotein (P) and nucleocapsid (N) genes strongly suggest that the BWMV represents a novel strain of CeMV present in Hawai'i and the Central Pacific. In contrast to recently reported isolates from Brazil and Australia that may represent a distinct clade, BWMV appears to be more closely related to known strains of CeMV (dolphin morbillivirus; porpoise morbillivirus; and pilot whale morbillivirus). Detection rates with repeat sampling of positive lymph nodes were between 2 and 61%, illustrating the extreme heterogeneity that can occur in affected tissues. Taken together, these results suggest that BWMV may be common and established in Hawaiian cetacean populations. BWMV will be important for understanding CeMV and health threats in the relatively understudied cetaceans of the Pacific.

Diagnosis of Cetacean morbillivirus: A sensitive one step real time RT fast-PCR method based on SYBR® Green

Cetacean morbillivirus (CeMV) (family Paramyxoviridae, genus Morbillivirus) is considered the most pathogenic virus of cetaceans. It was first implicated in the bottlenose dolphin (Tursiops truncatus) mass stranding episode along the Northwestern Atlantic coast in the late 1980s, and in several more recent worldwide epizootics in different Odontoceti species. This study describes a new one step real-time reverse transcription fast polymerase chain reaction (real-time RT-fast PCR) method based on SYBR® Green to detect a fragment of the CeMV fusion protein gene. This primer set also works for conventional RT-PCR diagnosis. This method detected and identified all three well-characterized strains of CeMV: porpoise morbillivirus (PMV), dolphin morbillivirus (DMV) and pilot whale morbillivirus (PWMV). Relative sensitivity was measured by comparing the results obtained from 10-fold dilution series of PMV and DMV positive controls and a PWMV field sample, to those obtained by the previously described conventional phosphoprotein gene based RT-PCR method. Both the conventional and real-time RT-PCR methods involving the fusion protein gene were 100- to 1000-fold more sensitive than the previously described conventional RT-PCR method.

Novel Cetacean Morbillivirus in Guiana Dolphin, Brazil

To the Editor: Since 1987, morbillivirus (family Paramyxoviridae, genus Morbillivirus) outbreaks among pinnipeds and cetaceans in the Northern Hemisphere have caused high rates of death (1,2). Two morbillivirus species are known to affect aquatic animals: Phocine distemper virus (PDV) and Cetacean morbillivirus (CeMV). PDV has been isolated from pinnipeds, and 3 strains of CeMV (porpoise morbillivirus [PMV], dolphin morbillivirus [DMV], and pilot whale morbillivirus [PWMV]) have been isolated from dolphins and whales (3,4). Serologic surveys indicate that morbilliviruses infect marine mammals worldwide (5); however, only 1 fatal case in a bottlenose dolphin (Tursiops truncatus) has been confirmed in the Southern Hemisphere (in the southwestern Pacific Ocean) (6). Positive DMV-specific antibody titers in 3 Fraser’s dolphins (Lagenodelphis hosei) stranded off Brazil and Argentina in 1999 indicate the exposure of South Atlantic cetaceans to morbillivirus (7). We report a case of lethal morbillivirus infection in a Guiana dolphin (Sotalia guianensis), a coastal marine and estuarine species that occurs off the Atlantic Coast of South and Central America. A female Guiana dolphin calf (108 cm in total body length) (8) was found stranded dead in Guriri (18°44’S; 39°44’W), Sao Mateus, Espirito Santo State, Brazil, on November 30, 2010; the dead calf was severely emaciated. Postmortem examination of the animal showed multifocal ulcers in the oral mucosa and genital slit, diffusely dark red and edematous lungs, and congested and edematous brain. Samples of selected tissues were collected, fixed in buffered formalin, and processed according to routine histopathologic methods. By microscopy, the most noteworthy lesions included marked lymphoplasmacytic and neutrophilic meningoencephalitis, optic nerve perineuritis, and hypophysitis. Lungs showed moderate acute diffuse lymphoplasmacytic and neutrophilic interstitial pneumonia; severe multicentric lymphoid depletion and multifocal necrotizing hepatitis were also observed. Immunohistochemistry was performed by using CDV-NP MAb (VMRD, Inc., Pullman, WA, USA), a monoclonal antibody against the nucleoprotein antigen of canine distemper virus that cross-reacts with cetacean morbilliviruses (9). Known positive and negative control tissues and test sections with omitted first-layer antibody were included. Viral antigen was detected in neurons in the brain, bronchiolar epithelium and macrophages in the lungs, bile duct epithelium in the liver, and macrophages and lymphocytes in lymph nodes. We extracted RNA from frozen lung samples by using TRIzol Reagent (Life Technologies Corporation, Carlsbad, CA, USA) according to the manufacturer’s instructions and amplified a 374-bp conserved fragment of the phosphoprotein (P) gene by reverse transcription PCR. The following Morbillivirus spp.–specific primers were used for PCR: 5′-ATGTTTATGATCACAGCGGT-3′ (forward) and 5′-ATTGGGTTGCACCACTTGTC-3′ (reverse) (3). MEGA5 (http://megasoftware.net/) was used to construct a neighbor-joining phylogenic tree based on the sequenced amplicon from this study (GenBank accession no. {type:entrez-nucleotide,attrs:{text:KF711855,term_id:566036178,term_text:KF711855}}KF711855) and 12 other GenBank sequences that represent the 6 morbillivirus species already described in the literature. The analysis placed the Guiana dolphin strain at the CeMV clade, but segregated it from the already described dolphin morbillivirus strains PMV, DMV, and PWMV (Figure). The sample shared 79.8% nt and 58.4% aa identity with PMV, 78.7% nt and 56.6% aa identity with DMV, and 78.7% nt and 57.1% aa identity with PWMV. Within the Morbillivirus spp., PDV shared the lowest sequence identity (51.1% nt and 26.8% aa). Figure Phylogenetic tree of a 374-bp conserved region from the phosphoprotein gene of a cetacean morbillivirus isolated from a Guiana dolphin (in boldface; GenBank accession no. {type:entrez-nucleotide,attrs:{text:KF711855,term_id:566036178,term_text:KF711855}} ... In summary, sequence analysis of the morbillivirus from the dead Guiana dolphin suggests that the virus is a novel strain of the CeMV species; this conclusion is supported by phylogenic analysis and geographic distribution of the virus and by its distinct host. Emaciation, marked lymphoid depletion, interstitial pneumonia, and meningoencephalitis are common findings in morbillivirus-infected animals (1,2). Together with antigenic and genomic evidence, our findings indicate that morbillivirus infection is extant in Guiana dolphins in the waters off Brazil. Morbillivirus outbreaks have caused a high number of deaths among pinnipeds and cetaceans and are a major risk to previously unexposed nonimmune populations of aquatic mammals (1,2). A high number of morbillivirus-related deaths have not yet been reported among aquatic mammals in the waters off Brazil, but our findings shows that Guiana dolphin calves are susceptible to infection. Subclinical morbillivirus infection with immune suppression has been reported in bottlenose dolphins in Florida (10). It is unknown whether subclinical infection occurs in this host population or whether the virus has undergone species-adaptive changes, as proposed for PWMV (4). The sequence data from our study suggest that the virus from the Guiana dolphin calf is the fourth member of the CeMV group and is closer to the root of the CeMV clade than to that of DMV, PMV, or PWMV. Further studies are required to determine the epidemiology of morbillivirus infection in this and other cetacean species and to assess the risk for epizootic outbreaks among South Atlantic cetaceans.

Simultaneous diagnosis of Cetacean morbillivirus infection in dolphins stranded in the Spanish Mediterranean sea in 2011 using a novel Universal Probe Library (UPL) RT-PCR assay

A highly sensitive and specific real-time (rt) RT-PCR assay has been developed for rapid, simultaneous detection of three strains of cetacean morbillivirus (CeMV). In this assay, two PCR primers and a hydrolysis probe from a commercially available Universal Probe Library (UPL) are used to amplify a highly conserved region within the fusion protein gene. RT-PCR is carried out on the same sample using two primer sets in parallel: one set detects the more virulent strains, dolphin morbillivirus (DMV) and porpoise morbillivirus (PMV), and the other set detects the least virulent and least common strain, pilot whale morbillivirus (PWMV). Sensitivity analysis using dilute samples containing purified DMV, PMV and PWMV showed that viral RNA detection limits in this UPL RT-PCR assay were lower than in a conventional RT-PCR assay. Our method gave no amplification signal with field samples positive for viruses related and unrelated to CeMV, such as phocine distemper virus (PDV). The reliability and robustness of the UPL RT-PCR assay were verified using tissue samples previously analyzed by conventional methods, as well as a panel of clinical samples suspected of containing CeMV. Using the UPL RT-PCR assay, we were able to associate DMV with a mass stranding of striped dolphins in the Spanish Mediterranean in 2011 with greater reliability than was possible with a conventional RT-PCR method. These results suggest that this UPL RT-PCR method is more sensitive and specific than the conventional approach, and that it may be an affordable and rapid test for routine diagnosis of three CeMV strains.

Evidence of susceptibility to morbillivirus infection in cetaceans from the United States

AbstractCetacean morbilliviruses (CeMV) are viruses that can cause mass mortalities among various odontocete species. In this study levels of “herd” immunity in cetaceans from the U.S. coast are described from the distribution and prevalence of antibodies against morbilliviruses. Neutralizing antibody titers against dolphin morbillivirus (DMV), porpoise morbillivirus (PMV), phocine distemper (PDV), and canine distemper viruses (CDV) were measured. Positive samples had higher titers against the CeMV than against the other morbilliviruses tested, indicating that although PDV or CDV can be used to investigate exposure their use may result in a higher false negative rate. The results suggest that morbillivirus did not persist in coastal populations of bottlenose dolphins (Tursiops truncatus) after the major outbreaks that occurred in the 1980s and 1990s. Bottlenose dolphins from Beaufort, North Carolina; St. Joseph Bay, Florida; and Cape May, New Jersey had anti‐DMV seroprevalences ranging from between 15% and 33% but those from Charleston, South Carolina and Sarasota Bay, Florida, sampled in recent years were largely negative. These latter groups are therefore now vulnerable to infection and could experience high mortality if exposed to CeMV. Sero‐surveys of this kind are therefore vital for assessing the risk of new and recurring viral outbreaks in coastal cetaceans.

Morbillivirus and Toxoplasma Exposure and Association with Hematological Parameters for Southern Beaufort Sea Polar Bears: Potential Response to Infectious Agents in a Sentinel Species

Arctic temperatures are increasing in response to greenhouse gas forcing and polar bears have already responded to changing conditions. Declines in body stature and vital rates have been linked to warming-induced loss of sea-ice. As food webs change and human activities respond to a milder Arctic, exposure of polar bears and other arctic marine organisms to infectious agents may increase. Because of the polar bear's status as arctic ecosystem sentinel, polar bear health could provide an index of changing pathogen occurrence throughout the Arctic, however, exposure and monitoring protocols have yet to be established. We examine prevalence of antibodies to Toxoplasma gondii, and four morbilliviruses (canine distemper [CDV], phocine distemper [PDV], dolphin morbillivirus [DMV], porpoise morbillivirus [PMV]) including risk factors for exposure. We also examine the relationships between antibody levels and hematologic values established in the previous companion article. Antibodies to Toxoplasma gondii and morbilliviruses were found in both sample years. We found a significant inverse relationship between CDV titer and total leukocytes, neutrophils, monocytes, and eosinophils, and a significant positive relationship between eosinophils and Toxoplasma gondii antibodies. Morbilliviral prevalence varied significantly among age cohorts, with 1-2year olds least likely to be seropositive and bears aged 5-7 most likely. Data suggest that the presence of CDV and Toxoplasma gondii antibodies is associated with polar bear hematologic values. We conclude that exposure to CDV-like antigen is not randomly distributed among age classes and suggest that differing behaviors among life history stages may drive probability of specific antibody presence.

Phylogenetic analysis of a new Cetacean morbillivirus from a short-finned pilot whale stranded in the Canary Islands

Cetacean morbillivirus (CeMV) is considered the most pathogenic virus in cetaceans. Three strains have been already described: the dolphin morbillivirus (DMV), the porpoise morbillivirus (PMV) and the tentatively named pilot whale morbillivirus (PWMV). This study describes the molecular characterization of a strain of CeMV detected in the brain of a short-finned pilot whale that had stranded in the Eastern Atlantic Ocean around the Canary Islands and that showed lesions compatible with morbilliviral disease. Sequences for the nucleoprotein, phosphoprotein, fusion protein and haemagglutinin genes were obtained. The phylogenetic study showed high homology (97%) with the PWMV strain previously detected from a long-finned pilot whale stranded in the Western Atlantic Ocean. These results support the existing classification of CeMV into three principal genetic clusters.

Real-time RT-PCR assays for the rapid and differential detection of dolphin and porpoise morbilliviruses

Real-time RT-PCR (rtRT-PCR) assays for identifying and differentiating infections caused by dolphin morbillivirus (DMV) and porpoise morbillivirus (PMV) were developed by targeting the hypervariable C-terminal domain of the nucleocapsid (N) gene. Total DMV and PMV RNA extracted from infected Vero cells expressing the canine signaling lymphocyte-activation molecule (SLAM) produced positive cycle threshold (CT) values after the 17th and 25th cycles, respectively. The assays were then validated using infected cetacean tissue RNA. The assays were specific for either DMV or PMV and did not cross-react with canine distemper virus (CDV), phocid distemper virus (PDV), rinderpest virus (RPV), peste des petits ruminants virus (PPRV) and measles virus (MV). The glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene was targeted as control for RNA quality, and a consensus GAPDH probe that reacted with 11 different marine mammal species, generating positive CT values ranging from the 21st to the 37th cycle was used. The rtRT-PCR assays have advantages over conventional assays in that they are rapid, easier to scale up, and are less prone to cross-contamination and have improved the limit of detection and specificity.

Sequence of the nucleocapsid gene and genome and antigenome promoters for an isolate of porpoise morbillivirus

We have determined the first complete sequence of the nucleocapsid (N) gene of the porpoise morbillivirus (PMV) as well as the genome leader and trailer sequences which encode the genome and antigenome promoters, respectively. The PMV N gene is 1686 nucleotides long with a single open reading frame (ORF) encoding a protein of 523 amino acids with a predicted molecular weight of 57.39 kDa. The nucleotide sequence of the N gene shows the closest identity (89%) to that of another cetacean morbillivirus, dolphin morbillivirus (DMV). Lower degrees of identity were found with the other members of the morbilliviruses genus; 67% identity to PDV and RPV, 68% to PPRV, 69% to CDV and 70% to MV. The distance from the 3′ end of the genome up to the start of the N ORF is 107 nucleotides, identical to that found in all other morbilliviruses, and encompasses the genome promoter (GP) sequence. This promoter shows the same regions of conservation as found in other morbilliviruses with repeated CXXXXX motifs at positions 79–84, 85–90, and 91–96, the same bi-partite promoter arrangement found in many paramyxoviruses. The antigenome promoter (AGP) shows a similar arrangement, indicating a high degree of conservation in these functionally important regions.

Distemper in a Dolphin

To the Editor: Deaths caused by new members of the genus Morbillivirus, family Paramyxoviridae (1), have occurred in recent decades among phocine and cetacean species, particularly harbor seals (Phoca vitulina) in 1988 (2) and 2002 (3). Endangered Mediterranean striped dolphins (Stenella coeruleoalba) died in 1990 and 1991 (4), and common dolphins (Delphinus delphis ponticus) from the Black Sea died in 1994 because of infection with dolphin morbillivirus (DMV) (5). A similar virus caused deaths in bottlenose dolphins (Tursiops truncatus) in the Gulf of Mexico from 1987 through 1994 (6). Closely related morbilliviruses caused deaths in harbor porpoises (Phocoena phocoena) in European waters in 1988 (7) (Porpoise morbillivirus) and endangered Mediterranean monk seals (Monachus monachus) in 1997 (8) (Monk seal morbillivirus). After these epidemics, the viruses disappeared and no marine or terrestrial reservoirs have been identified.

Involvement of morbilliviruses in the pathogenesis of demyelinating disease

Two members of the morbillivirus genus of the family Paramyxoviridae, canine distemper virus (CDV) and measles virus (MV), are well-known for their ability to cause a chronic demyelinating disease of the CNS in their natural hosts, dogs and humans, respectively. Both viruses have been studied for their potential involvement in the neuropathogenesis of the human demyelinating disease multiple sclerosis (MS). Recently, three new members of the morbillivirus genus, phocine distemper virus (PDV), porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV), have been discovered. These viruses have also been shown to induce multifocal demyelinating disease in infected animals. This review focuses on morbillivirus-induced neuropathologies with emphasis on aetiopathogenesis of CNS demyelination. The possible involvement of a morbillivirus in the pathogenesis of multiple sclerosis is discussed.

Cetacean morbilliviruses are phylogenetically divergent

We performed a phylogenetic comparison of porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV) isolates from porpoises and dolphins respectively according to criteria adopted by the World Health Organization for the phylogenetic comparison of measles viruses. PMV and DMV were more divergent than the most distantly related measles virus strains, thus challenging the classification of PMV and DMV as two strains of a single species, cetacean morbillivirus.

Rinderpest and peste des petits ruminants viruses exhibit neurovirulence in mice.

Members of the morbillivirus genus, canine distemper (CDV), phocine distemper virus (PDV), and the cetacean viruses of dolphins and porpoises exhibit high levels of CNS infection in their natural hosts. CNS complications are rare for measles virus (MV) and are not associated with rinderpest virus (RPV) and peste des petits ruminants virus (PPRV) infection. However, it is possible that all morbilliviruses infect the CNS but in some hosts are rapidly cleared by the immune response. In this study, we assessed whether RPV and PPRV have the potential to be neurovirulent. We describe the outcome of infection, of selected mouse strains, with isolates of RPV, PPRV, PDV, porpoise morbillivirus (PMV), dolphin morbillivirus (DMV), and a wild-type strain of MV. In the case of RPV virus, strains with different passage histories have been examined. The results of experiments with these viruses were compared with those using neuroadapted and vaccine strains of MV, which acted as positive and negative controls respectively. Intracerebral inoculation with RPV (Saudi/81) and PPRV (Nigeria75/1) strains produced infection in Balb/C and Cd1, but not C57 suckling mice, whereas the CAM/RB rodent-adapted strain of MV infected all three strains of mice. Weanling mice were only infected by CAM/RB. Intranasal and intraperitoneal inoculation failed to produce infection with any virus strains. We have shown that, both RPV and PPRV, in common with other morbilliviruses are neurovirulent in a permissive system. Transient infection of the CNS of cattle and goats with RPV and PPRV, respectively, remains a possibility, which could provide relevant models for the initial stages of MV infection in humans.

Morbillivirus ecology in polar bears ( Ursus maritimus )

Polar bear (Ursus maritimus) morbillivirus infection was initially reported by Follmann and co-workers in 1996, based upon serologic results using canine distemper virus (CDV). The impetus for the evaluation of polar bear populations for morbillivirus infections was prompted by epidemics of canine distemper-like disease in seal populations in the north Atlantic regions of Greenland, Europe, and Russia. Since marine morbilliviruses have been further characterized into three major species, phocine distemper virus (PDV), dolphin morbillivirus (DMV) and porpoise morbillivirus (PMV), it was of value to determine the origin of the polar bear infection. One hundred serum samples were selected from a group of sera collected from regions of Alaska and Russia and tested by differential serum neutralization assay against the three major marine morbilliviruses and CDV, to determine the predominant virus infecting the polar bear. Polar bears had higher serum antibody titers to CDV than they did to PDV, DMV, and PMV. These data suggest that polar bears are being infected with a morbillivirus of terrestrial origin. Furthermore, based on the high serum antibody prevalence in the population, the virus may be indigenous to the polar bear and not necessarily the result of interspecies transmission from other arctic mammals susceptible to CDV and/or marine morbilliviruses.

Immunohistological and serological investigation of morbillivirus infection in harbour porpoises ( Phocoena phocoena) from the German Baltic and North Sea

The role of morbillivirus infection as a cause of disease or death in harbour porpoises (Phocoena phocoena) from the German North and Baltic Sea was investigated by serology, histology and immunohistochemistry. Blood and tissue samples of lung, brain and lymph nodes from 74 stranded or by-caught harbour porpoises from German waters were collected between 1991 and 1997. According to dentinal growth layers and body length, animals were grouped into four age classes (neonates, 0–1, 1–4, 4–16 years of age). Formalin-fixed, paraffin-embedded sections were stained by hematoxylin and eosin (HE). Immunohistology was done in all lung tissues using the avidin–biotin–peroxidase technique and a polyclonal canine distemper virus (CDV) nucleoprotein-specific antibody, which cross-reacts with porpoise morbillivirus (PMV) antigen. A virus neutralization assay for detection of (Onderstepoort-strain) CDV- and PMV-specific antibodies was performed. Due to the cytotoxicity of some sera, only titres of 1:20 or greater were considered positive. PMV or CDV-specific neutralizing antibody titres were found in 88 and 50% of the animals, respectively. Titres were always highest against PMV indicating infection with a homologous porpoise virus strain. There were no significant differences in neutralizing antibody titres between animals of the different age groups. No histological lesions specific for morbillivirus infection were detected and by immunohistology all cases were negative for morbillivirus antigen. The absence of morbillivirus antigen and the lack of characteristic morbillivirus-specific lesions showed that morbillivirus infection was not a cause of death or illness in the investigated population. However, the high incidence of PMV-specific antibodies in all age groups indicated a continuous spread of infection with a morbillivirus among harbour porpoises from the German Baltic and North Sea.

Identification of morbilliviruses of probable cetacean origin in carcases of Mediterranean monk seals (Monachus monachus)

Two morbilliviruses were isolated from carcases of Mediterranean monk seals (Monachus monachus) which had died in coastal areas of Greece and Mauritania. They were characterised as being closely related to...

Molecular genetic evidence of a novel morbillivirus in a long-finned pilot whale (Globicephalus melas).

A long-finned pilot whale with morbilliviral disease was stranded in New Jersey. An immunohistochemical stain demonstrated morbilliviral antigen. Reverse transcriptase-polymerase chain reaction for morbillivirus P and N genes was positive. Novel sequences most closely related to, but distinct from, those of dolphin and porpoise morbilliviruses suggest that this virus may represent a third member of the cetacean morbillivirus group.