The objectives of this proposed work are to examine the factors that led to the recent emergence of Hendra virus (HeV) and Nipah virus (NiV) in Australia and southeast Asia. Substantial data implicate fruit bats as reservoir hosts for these viruses. Both moved into human populations via domestic animal “amplifier” hosts (horses for HeV and pigs for NiV) and caused fatal disease in humans. NiV in particular was responsible for the death of over 100 people in 1999. Little is known of the underlying causes of emergence, but three plausible factors have been proposed: encroachment; climate; and alterations to fruit bat migration patterns. Our aim is to investigate their role in emergence, and to set up a series of key experiments to understand the mode of transmission between host species more clearly.
These viruses are part of a growing group of novel zoonotic paramyxoviruses harboured by fruit bats. Their recent emergence, high case fatality rate in humans and the potentially large pool of other related viruses in fruit bats, suggests that these are a significant threat to human health beyond their current distribution. Understanding their emergence will have a significant impact on future surveillance and control programs. In particular, a component of this project is to develop a predictive, parameterized (via experimental and field data) mathematical model for NiV and HeV emergence. This model can be combined with insights into the role of environmental change in driving emergence, to significantly reduce the public health threat of these pathogens.
We have brought together a team of leading virologists, ecologists, medical researchers, modelers, wildlife disease biologists and wildlife biologists to work on this project. This group includes members of the team that originally discovered both HeV and NiV and who have conducted much of the further work on these viruses since their discovery. We have a leading virologist from CDC Special Pathogens Branch and a key Malaysian virologist to act as consultants and guide our progress throughout the period of the study. Our specific aims for work on HeV and NiV are to:
1) By serological and virological surveys, describe the geographic and distribution and bat host range of these viruses in Australia and southeast Asia.
2) Study the migration patterns of Malaysian and Australian fruit bats and assess whether anthropogenic changes have caused migratory routes to alter and led to emergence.
3) Develop improved diagnostic assays for detection of these and other flying fox associated paramyxoviruses.
4) Experimentally deduce the key routes of transmission/excretion of these viruses in bats, cats and pigs.
5) Build a simple GIS overlaid database to test the role of climatic variation (in particular ENSO) and anthropogenic fires in their emergence.
6) Use Malaysian Govt. data, “shoe-leather” epidemiology and historical analysis of case study farms to analyse recent changes in pig-farming and human population encroachment into fruit bat habitat in Malaysia.
7) Assess the temporal pattern of infection in bats and investigate natural routes of excretion.
8) Develop a parameterized, predictive mathematical model that describes the emergence of HeV and NiV, using data collected in all of the above studies.
Author: P. Daszak.