New Fruit Bat Viruses Affecting Horses, Pigs, and Humans

Abstract

This chapter describes a remarkable series of new zoonotic viruses, including Hendra virus (HeV) and Nipah virus (NV), that have emerged from fruit bats in Australia and Malaysia. An apparently new paramyxovirus was isolated as the causative agent and was called Menangle virus (MenV). An initial diagnosis of Japanese encephalitis was changed when a paramyxovirus was isolated from the brain of a person and quickly identified as a virus resembling HeV. It was subsequently confirmed in the farmers’ pigs and also in dogs, cats, and horses. The major pathological changes were bronchopneumonia, with syncytium formation in respiratory alveoli in some pigs, and some animals showed meningitis. In humans, the disease was largely confined to pig farmers and to some abattoir workers, possibly from respiratory excretions from the pigs. There is evidence of greater contact between humans and their domestic animals and the bats as we encroach on the rainforest. MenV, once it was introduced into pigs, affected large numbers of sows and their offspring as well as two humans. Four new viruses have been isolated that have fruit bats in southeast Asia and Australia as natural hosts. These were HeV, Australian bat lyssavirus (ABL), MenV, and NV. The first, HeV, was probably only isolated because it was from an outbreak of disease with numbers of animals and humans far greater than what would be expected from the virus's level of contagiousness.