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Jonathan Epstein, DVM, MPH and Peter Daszak, PhD. Wildlife Trust, The Consortium for Conservation Medicine, 61 Route 9W, Palisades, NY 10964, 845-365-8595, epstein@conservationmedicine.org
Within the past ten years 4 new paramyxoviruses have been isolated from fruit bats (genus Pteropus) in Australia and Southeast Asia, and two of these have emerged in humans resulting in significant human mortality. The first of these diseases to emerge was Hendra virus (HeV) in Australia in 1994. In1998, Nipah virus (NiV) emerged in pigs in Malaysia and resulted in the death of 105 people (40% case fatality) who worked on pig farms. Two species of flying fox, Pteropus vampyrus and P. hypomelanus, are the likely reservoirs for NiV. Human activities such as slash-and-burn deforestation, intensified pig farming, and agricultural encroachment on primary rainforest are believed to have played a central role in the emergence of NiV in Malaysia by altering bat foraging behavior and bringing bats into close contact with pig farms.
We are conducting the following studies: Spatial and temporal distribution of NiV in pteropid species in Australia and Malaysia; long-range movement of Australian and Malaysian flying foxes; epidemiologic surveys and mathematical modeling of henipavirus infections; assessment of climate, land use and agricultural changes in Malaysia and Australia prior to emergence; and experimental investigation of transmission dynamics and route of henipavirus infection.
A four-year longitudinal study of HeV in Australian fruit bats has not produced any virus from over 600 samples collected. Malaysian fruit bats are currently being tested for NiV. Data received from satellite transmitters on flying foxes have revealed undiscovered roosting sites and information on long-range movement. Experiments are underway to investigate modes of transmission of henipaviruses in bats and domestic animals.
HeV surveillance in bats suggests a low viral prevalence or a short viremic period with rapid clearing of infection. If NiV behaved similarly, there would be limited opportunity for spillover events. Intensification of pig farming may be more important than the overall expansion of pig farms in Malaysia, by sufficiently raising the host density to sustain an outbreak. Haze from forest-burning, increased hunting pressure, changes in availability of food, and the presence of fruit plantations next to pig farms, may have sufficiently changed movement patterns of P. vampyrus so it was brought into close proximity of the index farm allowing for NiV transmission.
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Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.