Discovery of Swine as a Host for the Reston ebolavirus

Not Reston at All Reston ebolavirus is named, mistakenly perhaps, for Reston, Virginia, where it was discovered in the 1970s in imported macaques. After some alarm it was found not to be virulent in humans, uniquely among the ebola viruses, which are characteristically fatal causing a horrific spectrum of symptoms. Using a panviral detection assay, Reston ebolavirus has been rediscovered by Barrette et al. (p. 204) in domesticated pigs in the Philippines in association with other viruses that cause respiratory illness. The strains involved are closely related to the original macaque strain and, given how little variance there is among the viruses, it appears that it is freely circulating between these species possibly, like several other zoonotic viruses, having a reservoir in bats. Serological assays indicated that farm workers have become infected, although no obvious symptoms of human disease have been reported. Respiratory infections in pigs in the Philippines are associated with a cocktail of viruses, including a monkeys filovirus. Since the discovery of the Marburg and Ebola species of filovirus, seemingly random, sporadic fatal outbreaks of disease in humans and nonhuman primates have given impetus to identification of host tropisms and potential reservoirs. Domestic swine in the Philippines, experiencing unusually severe outbreaks of porcine reproductive and respiratory disease syndrome, have now been discovered to host Reston ebolavirus (REBOV). Although REBOV is the only member of Filoviridae that has not been associated with disease in humans, its emergence in the human food chain is of concern. REBOV isolates were found to be more divergent from each other than from the original virus isolated in 1989, indicating polyphyletic origins and that REBOV has been circulating since, and possibly before, the initial discovery of REBOV in monkeys.