Orthoreovirus

Abstract

Etiology • Orthoreoviruses are non-enveloped, segmented RNA viruses in the family Reoviridae. • There are 5 known species in the genus Orthoreovirus, of which species I is referred to as mammalian orthoreovirus (MRV) or mammalian reovirus. Within this species, there are four distinct serotypes. • Serotypes 1-3 of MRV, as well as antibodies to each, have been detected in swine. • A novel pathogenic strain of serotype 3 (MRV3) was reported in U.S. swine herds in 2015. Cleaning and Disinfection • Some porcine MRV isolates are susceptible to one hour of 50˚C heat (122˚F); however, the recently discovered U.S. strains are stable at 56˚C (133˚F) and remain viable after exposure to 80˚C (176˚F) or 90˚C (194˚F) for up to one hour. • Specific information on the disinfection of porcine MRV is lacking. Orthoreoviruses are generally stable over a wide pH range and resistant to ether, chloroform, and lipid solvents. They are potentially susceptible to 0.1% sodium deoxycholate. Epidemiology • Orthoreoviruses are ubiquitous, infecting a large variety of animal species over a wide geographic range. In addition to pigs, evidence of orthoreovirus infection has been seen in cattle, sheep, horses, goats, primates, bats, birds, dogs, cats, rabbits, rodents, marsupials, civet cats, and reptiles. • Zoonotic transmission of orthoreoviruses is possible, although sustained human-to-human transmission has not yet been observed. Illness is most commonly mild and self-limiting; however, more severe respiratory or neurologic forms of the disease have occurred. There have been no reports of porcine MRV infecting humans. • While MRV is geographically widespread, infection of swine has only been reported in China, Japan, South Korea, and the U.S. Transmission • Transmission of MRV in pigs is known to occur by the fecal-oral route. The virus has also been detected in nasal secretions, respiratory aerosols, and fetal tissues.