Abstract

Over the past 10 years, flying foxes (family Pteropodidae, genus Pteropus) have been identified as reservoirs for several emerging zoonotic diseases in South and Southeast Asia and the western Pacific.^1,2 Hendra virus (HeV) and Nipah virus (NiV) are associated with a high case-fatality rate, with HeV killing two of the three human cases in Australia and Nipah virus causing the death of nearly 40% of its cases in Malaysia (n=265), as well as being associated with several recurrent and late-onset infections in survivors.^3-5 These two pathogens have been described as members of a new genus of paramyxovirus: Henipavirus. The Nipah virus outbreak in Malaysia also had very significant economic effects, with the destruction of over one million pigs leading to the loss of over U.S. $400 million in swine export.⁶ Outbreaks of Nipah-like viruses in Bangladesh may have also stemmed from a flying fox reservoir.³ Preliminary data from this study suggests that flying foxes are capable of long-distance movement (>200 km) across geopolitical boundaries. Understanding the long-distance movements of flying foxes is particularly important for understanding the geographic distribution of henipaviruses, as well as interpopulation and interspecies transmission dynamics. Human activities such as deforestation, agricultural expansion, urbanization, global travel, and trade have been linked to the emergence of zoonotic pathogens from wildlife by altering the ecology of wild animal species, creating more opportunities for spillover of zoonotic pathogens into humans via increased contact either between humans and wildlife, or wildlife and domestic animals.⁷ From a conservation perspective, flying foxes play a critical role in rainforest propagation by dispersing seeds and pollinating flowers, and, therefore, efforts must be made to promote their conservation rather than vilifying them as hosts for deadly disease. The Henipavirus Collaborative Research Group, funded through the NIH Fogarty International Center, is studying the distribution and long-range movement patterns of pteropid bats where NiV and HeV have emerged as a part of a large-scale ecological study. This study was designed to test the hypothesis that human environmental pressures such as agricultural expansion, deforestation, and hunting have altered flying fox behavior, which has acted as a driver for Henipavirus emergence. This report discusses preliminary findings from our initial cohort of satellite-collared flying foxes.

We placed platform terminal transmitters (PTTs) (Microwave Telemetry, MD, U.S.) on four flying foxes of species known to carry Hendra virus (Pteropus alecto) (n=3) or Nipah virus (Pteropus vampyrus) (n=1). The movements of three black flying foxes (Bat A, B, and C) in Australia and one Malaysian flying fox (Bat D) in peninsula Malaysia were followed using Argos satellite telemetry systems (Collecte Localisation Satellites, French Space Agency, France). Location data was imported into ArcView GIS 3.3 (ESRI, U.S.). Home range analysis was performed using the kernel analysis method available in the home range extension for ArcView GIS. Over a period of 120 days Bat A traveled 382 km to roost at four colonies, occupying a home range of 35,000 km², and was located foraging an average of 6.78 km from his roosting colony at night. Bats B and C remained in the same colony over a period of 143 and 128 days, occupying a home range of 11,000 and 1,000 km² and were located foraging an average of 5.3 and 2.7 km from their roosting colony at night, respectively. Bat D traveled 745 km over a period of 63 days, roosting at four colonies, occupying a home range of 150,000 km² and was located foraging an average of 18.08 km from his roosting colony at night. The accuracy of the Argos Service Location Class (3, 2, 1, 0, A, and B) errors were also compared with a known location to provide actual average errors (0.48, 0.82, 1.32, 8.13, 11.21, and 26.23 km, respectively). The number of bats with transmitters will be augmented in order to have a more scientifically representative data set. With an improved understanding of the long-range seasonal movements of pteropid bats, coupled with disease distribution data, we hope to be able to better describe the geographic distribution of henipaviruses in wildlife.

Acknowledgments

This study is funded by an NIH/NSF “Ecology of Infectious Diseases” award via the John E. Fogarty International Center of NIH, TW05869, and by core funding to the Consortium for Conservation Medicine from the V. Kann Rasmussen Foundation. We would like to thank the consultants to our group, Tom Ksiazek (CDC, Atlanta) and Sai Kit Lam (University of Malaya).

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