Porpoise Morbillivirus Research Articles

MORBILLIVIRUS INFECTION IN MANATEES

AbstractThe first evidence of exposure of free‐ranging Florida manatees (Trichechus manatees latirostris) to a morbillivirus is reported. Blood samples were collected from 148 Florida manatees between 1977 and 1994. The sample included manatees that were under rehabilitation (n = 97), free‐ranging (n = 40) and fresh necropsy specimens (n = 11). Serum from six animals (4%) neutralized porpoise and dolphin morbilliviruses to a higher titer than any other member of the Morbillivirus genus. Antibodies were not detected in sera from 12 free‐ranging Antillean manatees (T. manatus manatus) from Guyana sampled in 1992 or from 12 hand‐reared Amazonian manatees (T. inunguis) sampled in 1984. Immunoprecipitation studies using radio‐labelled canine distemper virus protein and serum from Florida manatees showed precipitation of the nucleo‐capsid (N) protein. The combination of low antibody titers and absence of clinical disease suggest that the Florida manatee is a dead‐end host. Sporadic infection may occur following contact with another species in which infection is enzootic. Morbillivirus could, either by fatal infection or more insidious effects on the immune system or reproduction, pose a problem to this already threatened species.

The evolution of morbilliviruses: a comparison of nucleocapsid gene sequences including a porpoise morbillivirus

Sequence data for the nucleocapsid protein (N) gene of the porpoise morbillivirus including the very conserved middle section of the protein and the hypervariable C terminus are reported. Analysis of dissimilarity indices based on an alignment of the N proteins of various morbilliviruses identifies a variable region of the N protein from amino acids residues 121 to 145 and a hypervariable part from amino acids 400 to 517. This type of analysis can be usefully applied when protein sequences of five or more morbillivirus species are available. Regions of variability between species identified by this index also represent regions of variation within one species e.g. measles virus (MV). Hence, comparative analysis of different morbilliviruses provides an insight into the potentially variable parts of viral proteins. From the great and unexplained nucleotide sequence conservation observed within MV, it would appear that the various morbilliviruses have diverged from each other a very long time ago. However, the data do not yet allow us to estimate the time span of these divergences. The relatedness and the number of different morbillivirus species provides a unique database for study of the evolution of RNA viruses.

Morbillivirus infection in cetaceans of the western Atlantic

We report serologic evidence of morbillivirus infection in eleven of fifteen species of odontocete cetaceans from the western Atlantic since 1986. Blood samples were obtained both from free-ranging and stranded animals. Virus neutralizing titers were higher against porpoise and dolphin morbilliviruses than against peste des petits ruminants virus, phocine distemper virus or canine distemper virus (CDV). Serum from five species, tested in a heterologous immunoprecipitation assay using radio-labelled CDV, precipitated the nucleocapsid (N) protein. Clinical morbillivirus infection may potentially impact already threatened species such as the harbour porpoise and precipitate mass strandings of socially cohesive odontocetes.

Nucleotide and deduced amino acid sequences of the matrix (M) and fusion (F) protein genes of cetacean morbilliviruses isolated from a porpoise and a dolphin ☆

Morbilliviruses have been isolated from stranded dolphins and porpoises. The present paper describes the cloning and sequencing of the porpoise morbillivirus (PMV) F gene and of the dolphin morbillivirus (DMV) M and F genes and their flanking regions. The gene order of the DMV genome appeared to be identical to that of other morbilliviruses, A genomic untranslated region of 837 nucleotides was found between the translated DMV M and F gene regions. The predicted DMV M protein were highly conserved with those of other morbilliviruses. Both the deduced PMV and DMV F 0 proteins exhibited three major hydrophobic regions as well as a cysteine rich region, a leucine zipper motif and a cleavage motif allowing cleavage of the F 0 protein into F 1 and F 2 subunits. Apparently the DMV F 0 cleavage motif was not modified by adaptation of DMV to Vero cells. The predicted PMV and DMV F proteins were 94% identical. Comparisons with the corresponding sequences of other morbilliviruses demonstrated that the cetacean morbillivirus does not derive from any known morbillivirus but represents an independent morbillivirus lineage.

Characterization of morbilliviruses isolated from dolphins and porpoises in Europe

A previously unidentified morbillivirus was isolated from two harbour porpoises (Phocoena phocoena) that had died in the Dutch Waddensea (North Sea) in 1990. This porpoise morbillivirus (PMV) and a dolphin morbillivirus (DMV), which had recently caused a heavy mortality in Mediterranean striped dolphins (Stenella coeruleoalba), were compared antigenically with other members of the genus Morbillivirus, including the newly recognized phocine distemper virus type 1. DMV and PMV proved to be similar but distinct morbillivurses, closely related to rinderpest virus and peste-des-petitsruminants virus. Cell cultures of cetacean, pinniped, ruminant and canine origin showed a different pattern of susceptibility to DMV and PMV infection. Ruminants and dogs proved to be susceptible to experimental infection with DMV and PMV, which both caused a transient leukopenia most pronounced in the ruminants. Pre-exposure of dogs to DMV and PMV protected them from developing CDV viraemia and clinical signs upon challenge infection with virulent CDV. A serological survey among stranded animals of different cetacean species in Europe indicated that infections with DMV- and PMV-like morbilliviruses are not uncommon among these aquatic mammals.

Dolphin and Porpoise Morbilliviruses Are Genetically Distinct from Phocine Distemper Virus

The morbilliviruses recently isolated from two cetacean species in the North and Mediterranean Seas have been shown to differ from phocine distemper virus isolated from European seals using monoclonal antibodies. We have identified a "universal" morbillivirus primer set, based on highly conserved regions of the morbillivirus phosphoprotein (P) gene and used this to amplify a region surrounding the RNA editing site from all known members of the group. Sequence analysis of this region of the gene shows that the dolphin and porpoise viruses are related but quite different from all other members of the group, forming a distinct lineage more closely related to the ruminant morbilliviruses than to the carnivore viruses.

Pathologic and immunocytochemical studies of morbillivirus infection in striped dolphins (Stenella coeruleoalba).

Hundreds of striped dolphins (Stenella coeruleoalba) died along the Spanish Mediterranean coast during the second half of 1990. We necropsied 58 dolphins. Partial collapse of the lungs with patchy atelectasis, subcutaneous edema, icterus, and stomatitis were the most prominent gross morphologic changes. Histologically, a bronchiolo-interstitial pneumonia was the most frequent lesion (72% of the animals). It was characterized by hyperplasia of alveolar epithelial type II cells and formation of multinucleate syncytia in alveolar and bronchiolar lumina. Other prominent lesions were encephalitis (69%), lymphoid depletion, and formation of multinucleate syncytia in the cortex of lymph nodes. The distribution of morbillivirus antigen was investigated in 23 well-preserved dolphins using a monoclonal antibody against the hemagglutinin glycoprotein of phocine distemper virus. Positive immunostaining was found in brain (77%), in lung (70%), and in mesenteric (61%), mediastinal (47%), and prescapular (45%) lymph nodes. Phocine distemper virus antigen was demonstrated less frequently in trachea, stomach, biliary epithelium, intestine, kidney, and mammary gland. Necrotizing-hemorrhagic pneumonia and encephalitis due to Aspergillus fumigatus were seen in three dolphins, whereas two animals had lesions of toxoplasmosis. Changes in our dolphins were similar to those caused by distemper in seals and porpoises. The origin of the dolphin virus and the relationships among dolphin, seal, and porpoise morbilli viruses are unknown.