Molecular epidemiology and genome analysis of feline morbillivirus in household and shelter cats in Thailand.

BACKGROUND: Feline morbillivirus (FeMV) has been discovered in domestic cats associated with tubulointerstitial nephritis, but FeMV is also detected in healthy cats. This research aimed to identify and characterize the FeMV strains detected in a Thai cat population. RESULTS: Two-hundred and ninety-two samples (131 urine and 161 blood) derived from 261 cats (61 sheltered and 200 household cats) were included for investigating the FeMV prevalence using real-time reverse transcription PCR. The overall prevalence of FeMV detection was 11.9% (31/261) among both samples, which accounted for 14.5% (19/131) and 7.5% (12/161) of the urine and blood samples, respectively. Among the FeMV-PCR positive cats, the FeMV-detected prevalence was insignificantly associated with healthy cats (58.1%; 18/31) or urologic cats (41.9%; 13/31). Full-length genome analysis of these FeMV-Thai strains revealed that their genomes clustered together in the FeMV-1A clade with up to 98.5% nucleotide identity. Selective pressure analysis showed that overall FeMV-1 has undergone negative selection, while positive selection sites were more frequently observed in the phosphoprotein gene. CONCLUSIONS: The detected FeMV infections in the Thai cat population were not correlated with urologic disorders, although the virus was more detectable in urine samples. The genetic patterns among the FeMV-1 Thai strains were more consistent. A large-scale study of FeMV in Thai cat samples is needed for further elucidation.

Development of an ELISA for serological detection of feline morbillivirus infection.

Feline morbillivirus (FeMV), a member of the family Paramyxoviridae, is an emerging virus that was discovered in 2012. Despite the importance of FeMV infection in cats because of its postulated involvement in kidney diseases, no simple serological assay has been reported in its detection. Here, FeMV phosphoprotein (P protein) was expressed and purified as a glutathione-S-transferase (GST)-fusion protein and used for an enzyme-linked immunosorbent assay (ELISA) to detect FeMV-specific antibodies. With a cutoff value determined by immunoblotting, anti-FeMV P protein was detected with this assay in 22 (22%) of the 100 cat plasma samples collected from various regions of Japan. This ELISA is useful for epidemiological and immunological studies, as well as for diagnosis of FeMV infection.

Epidemiological and pathological study of feline morbillivirus infection in domestic cats in Japan.

BACKGROUND: Feline morbillivirus (FmoPV) is a novel paramyxovirus found to infect domestic cats. FmoPV has been isolated in several countries in Asia and Europe and is considered to have genetic diversity. Also, it is suspected to be associated with feline renal diseases including tubulointerstitial nephritis (TIN), which affects domestic cats with a high incidence rate. RESULTS: To clarify the state of FmoPV infection among domestic cats in Japan, an epidemiological survey was conducted. Twenty-one out of 100 cats were found to have serum antibodies (Ab) against FmoPV-N protein by indirect immunofluorescence assay (IF) using FmoPV-N protein-expressing HeLa cells. Twenty-two of the cats were positive for FmoPV RNA in the urine and/or renal tissues. In total, 29 cats were positive for Ab and/or viral RNA. These FmoPV-infected cats were classified into three different phases of infection: RNA+/Ab + (14 cats), RNA+/Ab- (8 cats) and RNA-/Ab + (7 cats). In immunohistochemistry (IHC), 19 out of 29 cats were positive for FmoPV-N protein in kidney tissues; however, the FmoPV-N protein was located in the inflammatory lesions with severe grade in only four out of the 19 cats. Since 15 out of 29 infected cats were positive for viral RNA and Ab, approximately half of the infected cats were persistently infected with FmoPV. CONCLUSIONS: A statistically significant difference was observed between infection of FmoPV and the presence of inflammatory changes in renal lesions, indicating a relationship between FmoPV infection and feline renal diseases. However, we could not obtain histopathological evidence of a relationship between FmoPV infection and TIN.

Morbillivirus infection in a wild siberian tiger in the Russian Far East.

We report the first documented case of morbillivirus infection in a wild, free-ranging Siberian tiger (Panthera tigris altaica). The tigress entered a small village in the Russian Far East in an ambulatory but stuporous state with no apparent recognition or fear of humans. Her condition progressed rapidly with neurological signs, anorexia, and ultimately death. Histologic lesions included vacuolated to malacic white matter in the brain stem, cerebellum, and thalamus, with associated lymphocytic meningoencephalitis. Large, intranuclear, eosinophilic inclusions were within regional astrocytes, and the brain lesions were immunohistochemically positive when stained for canine distemper viral antigen. Hematologic and blood chemistry results were consistent with overwhelming systemic infection and starvation. The animal also was antibody-positive for canine distemper virus, feline panleukopenia, and feline coronavirus.

Immunohistological and serological investigations of morbillivirus infection in Black Sea harbour porpoises (Phocoena phocoena).

In the present study the occurrence of morbillivirus infection in harbour porpoises (Phocoena phocoena) from the Black Sea was investigated. Blood and tissue specimens of lung, brain and spleen from 73 stranded or by-caught harbour porpoises derived from the three Black Sea subregions such as Bulgaria, Georgia and Ukraine were collected between 1997 and 1999 and processed for histology, immunohistochemistry and serology. Age determination was performed according to dental growth layers and body length. The age of the investigated population ranged from neonates to a 12-year-old animal. Morbillivirus-specific neutralizing antibodies were detected in 53% of harbour porpoises. Generally, titres were very low and ranged from 20 to 270. There was no correlation between age, geographical origin and titre levels. The most common histological finding (97%) consisted of a mild to severe granulomatous bronchopneumonia due to lung worm infection. There were no changes indicative of a morbillivirus infection. Using immunohistology none of the animals were positive for morbillivirus antigen. However, the serological data are suggestive of a continuously circulating morbillivirus among harbour porpoises from the Black Sea indicating that harbour porpoises may serve as carriers for fatal diseases in susceptible cetacean species.

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.

Comparative antibody response in harbour and grey seals naturally infected by a morbillivirus.

The antibody response of free-ranging harbour and grey seals, naturally infected by a morbillivirus, was assessed using a virus neutralizing test and a radio-immunoprecipitation assay. The prevalence of antibody was similar between species, however, grey seals had significantly higher virus neutralizing titers. Serum from clinically healthy grey seals precipitated the nucleocapsid (N) protein along with the hemagglutinin (H) and fusion (F) glycoproteins. By contrast, significantly fewer harbour seal sera precipitated the envelope glycoproteins and responses were weaker than those of grey seals. One harbour seal with acute morbillivirus pneumonia, and two with encephalitis precipitated only the N protein. Serum from four harbour seals with encephalitis weakly recognized the envelope glycoproteins. Thus, the antibody response of grey seals appears more competent than that of harbour seals with respect to morbillivirus antigens. We speculate that this difference between the species may be an important determinant of morbillivirus susceptibility.

Expression of equine morbillivirus (EMV) matrix and fusion proteins and their evaluation as diagnostic reagents.

Full-length cDNA clones coding for the matrix (M) and fusion (F) proteins of equine morbillivirus (EMV) were isolated by RT-PCR, and expressed in Escherichia coli using two different expression systems. Western blot analysis indicated that the M and F proteins, expressed either by itself or as fusion proteins with glutathione S-transferase (GST), were insoluble and degraded after expression. Analysis of the degradation pattern of recombinant M protein suggested that the N-terminus of the matrix protein might be more stable and antigenic than the C-terminal region. Therefore a third system was used to express a truncated M protein, composed of the N-terminal amino acid residues 1-197, with a (His)6-tag attached at the N-terminus. This recombinant protein [(His)6-Mtr], was stable but was also insoluble. After one-step affinity purification under denaturing conditions, (His)6-Mtr was used to monitor the antibody response to EMV infection by Western blot and ELISA. We obtained a 100% correlation between Western blot and virus neutralisation testing although the number of positive sera available for testing was very limited, which included seven horse, two rabbit and one human sera.

Serological evidence of morbillivirus infection in polar bears (Ursus maritimus) from Alaska and Russia.

One-hundred-and-ninety-one samples of blood serum collected from 186 polar bears (Ursus maritimus) between 1987 and 1992 were analysed for morbillivirus antibodies. The samples were collected in the Bering, Chukchi and East Siberian seas. Sixty-eight samples (35.6 per cent) had morbillivirus antibody titres > 5; the percentage of positive samples ranged from 26.2 to 46.2 per cent from year to year. The proportions of adults, sub-adults and cubs which were seropositive were 43.9, 35.7 and 37.9 per cent respectively. Some seropositive dams had seronegative young and some that were seronegative had seropositive young. One litter of two cubs, in which the dam was seronegative, had one seropositive and one seronegative cub. Seropositive bears occurred in all the areas from which the samples were collected but there was a significantly greater incidence in the bears sampled in Russia. The high prevalence of seropositive bears over the period suggests that the bear morbillivirus is endemic in these regions of the Arctic, but its source is unknown.

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 radiolabelled 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.