We previously discussed infection of zoo elephants with endotheliotropic elephant herpesvirus in This Week in Virology episode #7. A recent report in Emerging Infectious Diseases indicates that another herpesvirus, equine herpesvirus 9, is also infecting zoo animals. In July 2007, a polar bear in the San Diego Zoo developed encephalitis and was subsequently euthanized. Polymerase chain reaction was used to identify EHV-9 in the animal’s brain. The virus was also identified in members of a herd of Grevy’s zebras which was housed in close proximity to the polar bear. The authors of the study speculate that the virus was transmitted from the zebras to the polar bear by fomites (contaminated objects).
EHV-9 has been previously shown to cause encephalitis in Thomson’s gazelles and giraffes. EHV-9 and the highly related EHV-1 are endemic in horses. EHV-9 can also infect other animal species, including primates. The studies discussed here demonstrate that the host range of this virus is broader than previously known.
With respect to virus infections, zoos appear to be a microcosm of the wild. The ability to rapidly and definitively identify the etiologic agents of viral diseases in zoos has changed how we view infection of a broad range of animal species. Studies of the kind reported here will provide a great deal of information about viral pathogenesis, tropism, and host range.
The Department of Veterinary Science at the University of Kentucky College of Agriculture has an excellent website on diseases of the horse caused by equine herpesviruses.