Zoonotic risk: The Reston ebolavirus can infect pigs... and humans

The pathogenicity of the Reston Ebola virus in pigs is becoming clearer, with a new study establishing viable intraspecies transmission. Health authorities are concerned about the potential zoonotic role of pig populations in spreading the virus to humans.   The Reston virus (RESTV) is one of six known viruses in the genus Ebolavirus. It causes clinical disease in macaques and other non-human primates, but unlike the other five ebolaviruses, it causes only rare asymptomatic infections in humans. First described in 1989 in monkeys, the virus has been a particular cause for concern since January 2008, when it was detected in pigs in the Philippines. The first cases of cross-species transmission of RESTV between pigs and humans were then documented, prompting the World Health Organization to issue a global alert. Reston Ebola virus infection thus poses a zoonotic risk that raises public health concerns, particularly regarding food safety. This has raised numerous questions about the risks to humans. Until now, the pathogenicity in naturally infected pigs remained uncertain, with only a single experimental study demonstrating their susceptibility and ability to shed the virus, but without clinically developing the disease. A new study provides further insight into the pathogenicity of RESTV in pigs. Recent research has established significant virulence in pig populations. Yorkshire crossbred piglets—frequently used in breeding—that were experimentally infected with the Reston Ebola virus developed severe, even fatal, respiratory disease regardless of their age (three to seven weeks) and exhibited shedding of the virus via the respiratory tract. Further studies will help determine whether co-infections with other swine viruses affect the virulence of RESTV and whether pigs play an important role in the spread of Ebola viruses. In the meantime, the Reston virus should be considered a pathogen of Livestock with zoonotic potential, capable of infecting other mammals, including humans. “The emergence of RESTV in pigs is a warning sign, as direct transmission to humans through contact with pigs or the food chain is a possibility,” say scientists at the National Institutes of Health. They fear that pigs may serve as “intermediate hosts or amplifiers of Ebola viruses.” So far, the Reston Ebola virus has not been isolated in pigs intended for human consumption in the United States, only in China and the Philippines. However, health authorities throughout Southeast Asia are conducting increased health surveillance.