Genetic and pathogenic characterization of a novel reassortant mammalian orthoreovirus 3 (MRV3) from a diarrheic piglet and seroepidemiological survey of MRV3 in diarrheic pigs from east China.

Mammalian orthoreoviruses (MRVs), which cause gastrointestinal and respiratory illness, have been isolated from a wide variety of mammalian species including bats, minks, pigs and humans. Here we report the isolation and genetic and pathogenic characterization of a novel MRV type 3 (MRV3), named MRV-ZJ2013, from the diarrheic feces of piglets in Zhejiang province, China. Genomic and phylogenetic analysis shows that MRV-ZJ2013 may have originated from reassortments among mink, bat, and pig MRVs, suggesting the hypothesis that interspecies transmission has occurred in pig herds. Neonatal piglets infected with MRV-ZJ2013 displayed mild clinical signs such as poor appetite and soft feces, but vomiting and diarrhea were not observed. Fecal virus shedding was detected only in three out of six piglets, each for one- or two-day post-infection. In contrast, piglets inoculated with a virulent porcine epidemic diarrhea virus (PEDV) strain as the control group had severe signs characterized by acute vomiting and watery diarrhea. These findings suggest that the virulence of MRV-ZJ2013, if any, was likely not significant compared to that of PEDV. A seroepidemiological survey of MRV by means of an indirect enzyme-linked immune-sorbent assay (ELISA) based on a recombinant MRV3 capsid protein sigma1 as antigen revealed a high seroprevalence (77%) in 1037 samples from diarrheic pigs of different ages from 24 herds in seven provinces of east China between 2015 and 2016, indicating that MRV3 is endemic in pig herds in China, and may contribute collectively to enteric disease along with other porcine pathogens.

Qin P ，Li H ，Wang JW ，Wang B ，Xie RH ，Xu H ，Zhao LY ，Li L ，Pan Y ，Song Y ，Huang YW ... -  《-》

A novel pathogenic Mammalian orthoreovirus from diarrheic pigs and Swine blood meal in the United States.

Since May 2013, outbreaks of porcine epidemic diarrhea have devastated the U.S. swine industry, causing immense economic losses. Two different swine enteric coronaviruses (porcine epidemic diarrhea virus and Delta coronavirus) have been isolated from the affected swine population. The disease has been reported from at least 32 states of the United States and other countries, including Mexico, Peru, Dominican Republic, Canada, Columbia, Ecuador, and Ukraine, with repeated outbreaks in previously infected herds. Here we report the isolation and characterization of a novel mammalian orthoreovirus 3 (MRV3) from diarrheic feces of piglets from these outbreaks in three states and ring-dried swine blood meal from multiple sources. MRV3 could not be isolated from healthy or pigs that had recovered from epidemic diarrhea from four states. Several MRV3 isolates were obtained from chloroform-extracted pig feces or blood meal in cell cultures or developing chicken embryos. Biological characterization of two representative isolates revealed trypsin resistance and thermostability at 90°C. NextGen sequencing of ultrapurified viruses indicated a strong homology of the S1 segment to mammalian and bat MRV3. Neonatal piglets experimentally infected with these viruses or a chloroform extract of swine blood meal developed severe diarrhea and acute gastroenteritis with 100% mortality within 3 days postinfection. Therefore, the novel porcine MRV3 may contribute to enteric disease along with other swine enteric viruses. The role of MRV3 in the current outbreaks of porcine epidemic diarrhea in the United States remains to be determined, but the pathogenic nature of the virus warrants further investigations on its epidemiology and prevalence. Porcine orthoreoviruses causing diarrhea have been reported in China and Korea but not in the United States. We have isolated and characterized two pathogenic reassortant MRV3 isolates from swine fecal samples from porcine epidemic diarrhea outbreaks and ring-dried swine blood meal in the United States. These fecal and blood meal isolates or a chloroform extract of blood meal induced severe diarrhea and mortality in experimentally infected neonatal pigs. Genetic and phylogenetic analyses of two MRV3 isolates revealed that they are identical but differed significantly from nonpathogenic mammalian orthoreoviruses circulating in the United States. The present study provides a platform for immediate development of suitable vaccines and diagnostics to prevent and control porcine orthoreovirus diarrhea.

Thimmasandra Narayanappa A ，Sooryanarain H ，Deventhiran J ，Cao D ，Ammayappan Venkatachalam B ，Kambiranda D ，LeRoith T ，Heffron CL ，Lindstrom N ，Hall K ，Jobst P ，Sexton C ，Meng XJ ，Elankumaran S ... -  《-》

Prevalence and genomic characteristics of a novel reassortment mammalian orthoreovirus type 2 in diarrhea piglets in Sichuan, China.

Mammalian orthoreovirus (MRV), which can infect almost all mammals, is a zoonotic virus. In this study, six strains of type 2 MRV (MRV2) were isolated from 7 diarrhea piglets from a farm that had an outbreak of diarrhea in piglets in 2018, which tested negative for porcine epidemic diarrhea virus (PEDV), porcine transmissible gastroenteritis virus (TGEV), porcine deltacoronavirus (PDCoV), and porcine group A rotavirus (RAV). The MRV2 isolate infected neonatal piglets, in which it induced severe diarrhea, while the virus was detected in multiple organs of piglets. Moreover, the complete genome of an MRV2 isolate was obtained, which was a novel reassortant MRV strain of human MRV, porcine MRV, chamois MRV, bat MRV, and mink MRV based on the nucleotide identity and phylogenetic tree. The S1 gene of isolate had eight unique amino acid mutations compared with available MRV2 S1 in the GenBank. To investigate the prevalence of this MRV2, 78 samples of diarrhea feces were collected from 10 pig farms in seven regions of Sichuan province. The obtained results showed that the positive rate of samples was 14% (11/78), and positive rate of farms was 60% (6/10), while the amplified fragments shared the identical amino acid mutations with the isolated strain, thus suggesting that this MRV2 strain was already prevalent in Sichuan province. The present study was first to isolate a pig-derived type 2 MRV strain in China, obtaining the complete genome of this strain, which furthers our understanding of the MRV2 epidemic and evolution.

Luo Y ，Fei L ，Yue H ，Li S ，Ma H ，Tang C ... -  《-》

Characterization of mammalian orthoreoviruses isolated from faeces of pigs in Zambia.

Harima H ，Sasaki M ，Kajihara M ，Gonzalez G ，Simulundu E ，Bwalya EC ，Qiu Y ，Okuya K ，Isono M ，Orba Y ，Takada A ，Hang'ombe BM ，Mweene AS ，Sawa H ... -  《-》

First identification of mammalian orthoreovirus type 3 in diarrheic pigs in Europe.

Lelli D ，Beato MS ，Cavicchio L ，Lavazza A ，Chiapponi C ，Leopardi S ，Baioni L ，De Benedictis P ，Moreno A ... -  《-》