Equine Herpesvirus 9 (EHV-9) Induced Encephalitis in Nonhuman Primates

Equine Herpesvirus 9 (EHV-9) is a new member of the equine herpesviruses which was isolated from Thomson’s gazelles (Gazella thomsoni) that died of fulminant encephalitis in a Japanese zoo (Fukushi et al., 1997; Yanai et al., 1998). Previously, experimental infections of EHV-9 were conducted in various species of animals other than primates to clarify the infectivity and virulence of this virus and to assess the emerging aspects of EHV-9 in zoo and domestic animal populations. EHV-9 caused fatal infections with fulminant encephalitis characterized by neuronal degeneration and necrosis as well as intra-nuclear inclusion bodies in rodents (Fukushi et al., 1997; Fukushi et al., 2000), goats (Taniguchi et al., 2000), pigs (Narita et al., 2000, 2001), dogs (Yanai et al., 2003a) and cats (Yanai et al., 2003b). Based on several experimental studies of EHV-9 involving various domestic animals such as dogs and cats often found in close proximity to humans, there were grave concerns that EHV-9 could be transmitted to humans through contact with affected animals or zebras through certain routes. In order to assess the risk of EHV-9 to humans, we tried to determine the infectivity of EHV-9 in non-human primates, including common marmosets (Callithrix jacchus) and cynomolgus macaques (Macaca fasciocularis), which have strong similarities to humans, using the nasal route.