Isolation and characterization of novel reassortant mammalian orthoreovirus from pigs in the United States

Abstract

Mammalian orthoreovirus (MRV) infects multiple mammalian species including humans. A United States Midwest swine farm with approximately one thousand 3-month-old pigs experienced an event, in which more than 300 pigs showed neurological signs, like “down and peddling”, with approximately 40% mortality. A novel MRV was isolated from the diseased pigs. Sequence and phylogenetic analysis revealed that the isolate was a reassortant virus containing viral gene segments from three MRV serotypes that infect human, bovine and swine. The M2 and S1 segment of the isolate showed 94% and 92% nucleotide similarity to the M2 of the MRV2 D5/Jones and the S1 of the MRV1 C/bovine/Indiana/MRV00304/2014, respectively; the remaining eight segments displayed 93%–95% nucleotide similarity to those of the MRV3 FS-03/Porcine/USA/2014. Pig studies showed that both MRV-infected and native contact pigs displayed fever, diarrhoea and nasal discharge. MRV RNA was detected in different intestinal locations of both infected and contact pigs, indicating that the MRV isolate is pathogenic and transmissible in pigs. Seroconversion was also observed in experimentally infected pigs. A prevalence study on more than 180 swine serum samples collected from two states without disease revealed 40%–52% positive to MRV. All results warrant the necessity to monitor MRV epidemiology and reassortment as the MRV could be an important pathogen for the swine industry and a novel MRV might emerge to threaten animal and public health.

Genetic diversity, reassortment, and recombination of mammalian orthoreoviruses from Japanese porcine fecal samples

“…In this study, while searching for porcine enteric viruses in Japan, we isolated five MRVs from 230 fecal samples of pigs with or without diarrhea by culturing them in MA-104 cells. Several other cell lines, including African green monkey kidney (Vero) cells [13-15, 19, 30-33], Madin-Darby Canine Kidney cells [16], primary porcine kidney cells [18], Madin-Darby bovine kidney cells [29], swine testicular cells [34], and N1380 cells [35],…”

“…Similarly, porcine MRV infections are considered asymptomatic in most cases. However, severe diarrheic outbreaks I pigs caused by MRV alone or co-infection with other pathogens have been reported in China, South Korea, the United States, and Italy [11][12][13][14][15][16].…”

Isolation and characterization of mammalian orthoreovirus from bats in the United States

“…Cross‐species transmission of bat MRVs infecting humans has also been documented 7,16–18,47,48 . Although MRVs have been detected in many species in the United States, including human, swine, bovine, bats, and deer, 11,14,18,20,21 the prevalence of MRVs and what kind of MRVs exist and circulate in bats in North America are poorly understood. In this study, we screened more than 900 bats collected in the United States and found that 4.4% of collected bats including 40 big brown bats and 1 red bat were positive to MRV; these bats were collected from Nebraska, Kansas, and Missouri.…”

“…In addition, we also tested the infection of isolated MRVs in primary or immortalized respiratory cell lines from different species including bat lung cells, swine immortalized NEC, swine BEC, and ferret TEC, which were infected with each virus at an MOI of 0.05, and the supernatants from each infected cell line were collected at 24 and 48 h postinfection (hpi). Virus titer was determined by the immunofluorescence assay using an anti‐reovirus capsid protein μ1C monoclonal antibody (10F6; DSHB) and the FITC‐labeled goat anti‐mouse IgG second antibody as described previously 21 …”

Isolation, molecular characterization, and disinfectants susceptibility of swine-carried mammalian orthoreoviruses in Japan in 2020–2022

“…MRV1 to 3 serotypes were isolated from pigs in worldwide [8,16,17,19,39] including Japan [6,7,11]. Some studies have shown that MRVs isolates caused severe symptoms and mortality in experimentally infected piglets and pigs [32,36], which means that MRVs have the potential to cause serious problems on swine industry. Although data on the surveillance in pig farms can help to control MRVs infection among pigs, the surveillance report in Japan is limited.…”