Flying Foxes, Horses, and Humans: a Zoonosis Caused by a New Member of the Paramyxoviridae

Abstract

This chapter describes the outbreaks of disease caused by Megamyxovirus zoonotic agent; provides an updated description of the virus, its genome, and its wildlife reservoir; and documents what is known of the pathology and pathogenesis of equine morbillivirus (EMV) infection. A severe outbreak of respiratory disease occurred in the second half of September 1994 in horses stabled in the Brisbane suburb of Hendra. The outcome of the outbreak was that 13 horses died. The trainer died after hospitalization with severe respiratory involvement, while the stable hand recovered after a protracted illness. Although horses had been moved off the property during this period, infection had not spread to distant sites and extensive surveillance showed that the virus was not active in horses or humans. In fluorescent-antibody tests, sera from naturally infected horses and humans reacted strongly with the fruit bat virus. Identical viruses were isolated from a range of tissues from horses infected during the initial outbreak and from a kidney of the deceased trainer. Morphologically the virus is a member of the family Paramyxoviridae. The pathology of field and experimental EMV infections in horses and experimental infections in cats has been described. It is sufficiently different from known members of the Paramyxoviridae to be considered a member of a new genus which bridges the two existing genera Paramyxovirus and Morbillivirus. The author proposes that consideration should be given to creating a new genus within the family Paramyxoviridae, subfamily Paramyxovirinae, to be called Megamyxovirus, with the type species being EMV.