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Letter
Henipavirus in Pteropus
vampyrus Bats, Indonesia
Indrawati Sendow,* Hume Ernest Field,†
John Curran,‡ Darminto,§ Chris Morrissy,¶ Greer Meehan,¶ Tim Buick,# and
Peter Daniels¶
*Research Institute for Veterinary Science, Bogor, Indonesia; †Department
of Primary Industries and Fisheries, Brisbane, Queensland, Australia;
‡Australian Quarantine and Inspection Service, Broome, Western Australia,
Australia; §Assessment Institute for Agricultural Technology, Malang,
Indonesia; ¶Commonwealth Scientific and Research Organization Australian
Animal Health Laboratory, Geelong, Victoria, Australia; and #Biosecurity
Australia, Canberra, Australian Capital Territory, Australia
Suggested
citation for this article
To the Editor: The emergence of Nipah virus (NiV) in Malaysia
in 1999 resulted in 265 known human infections (105 fatal), widespread
infection in pigs (with >1 million culled to control the outbreak),
and the collapse of the Malaysian pig export market (1).
As with the closely related Hendra virus (HeV) that emerged in Australia
in 1994 and caused fatal disease in horses and humans (2),
bats of the genus Pteropus (commonly known as flying foxes) were
identified as the major reservoir of Nipah virus in Malaysia (3,4).
This report describes a serologic survey of Pteropus vampyrus in
neighboring Indonesia.
We nonrandomly sampled 106 P. vampyrus bats from market sellers
on the Indonesian islands of Java and Sumatra during a 12-day period from
July 23 to August 3, 2002 (Figure). Bats were typically
caught locally by sellers. Screening by indirect enzyme-linked immunosorbent
assay with inactivated NiV antigen was done at the Research Institute
for Veterinary Science in Bogor, Indonesia. Virus neutralization tests
(VNT) with NiV and HeV were performed under biosafety level 4 conditions
at the Commonwealth Scientific and Research Organization (CSIRO) Australian
Animal Health Laboratory in Geelong, Australia. The gold-standard (6)
VNT results are presented here; a neutralizing titer >5 was
considered positive.
Serum samples from 32 bats neutralized NiV (median titer 20, range 5–160),
samples from 52 bats did not, and samples from 20 bats caused toxic reactions
in the cell sheet at dilutions <10 (n = 7), <20 (n = 9), or <40
(n = 4), precluding a definitive test outcome. Two bats had inadequate
samples for NiV VNT. Samples from 19 bats neutralized HeV (median titer
10, range 5–80), samples from 60 bats did not, and samples from 27 bats
caused toxic reactions at dilutions <10 (n = 18), <20 (n = 7), or
<40 (n = 2), precluding a definitive test outcome. Of the 70 bats whose
samples had a definitive outcome in both tests, 11 neutralized NiV only,
1 neutralized HeV only, and 17 neutralized both viruses. Of these 17 bats,
14 samples had a higher titer to NiV than to HeV, 2 had identical titers
to each virus (5 and 10), and 1 had a higher titer to HeV (40) than to
NiV (20). Infection was attributed to NiV in 25 bats (11 whose samples
neutralized only NiV and 14 whose sera neutralized both viruses but had
a higher titer to NiV), a prevalence of 35.7% (95% confidence interval
[CI] 24.6%–48.1%). Infection was attributed to HeV in 2 bats (1 had a
HeV titer of 5 and no NiV titer, and the second had a HeV titer of 40
and a NiV titer of 20), a prevalence of 2.9% (95% CI 0.3%–9.9%).
The detection of antibodies that neutralized NiV at all 3 sampling locations
indicates that infection with NiV (or a cross-neutralizing virus other
than HeV) is widespread in P. vampyrus in Sumatra and Java. These
findings, in conjunction with earlier findings in peninsular Malaysia,
suggest that NiV infection is likely to be found in P. vampyrus
across its entire range (Figure). Recent satellite
telemetry studies showing regular P. vampyrus movements from Malaysia
to Sumatra and Thailand also support this contention (7).
Additionally, experience with HeV in Australian flying fox populations
suggests that where susceptible flying fox species share communal roosts,
evidence of infection is seen in in-contact species (8).
Therefore, NiV (or a Nipah-like virus) infection probably occurs in other
Pteropus species whose geographic distributions overlap or abut
that of P. vampyrus. This contention is supported by the positive
NiV serologic findings in P. lylei in Cambodia in 2002 (9)
and P. giganteus in India (J. Epstein et al., unpub. data) and
Bangladesh (10).
Infection was attributed to HeV in only 2 bats. The finding of 2 true
HeV-positive bats in Medan and Jakarta would require sporadic HeV infection
in a population in which NiV infection predominates or, alternatively,
nomadic movement of animals from a population in which HeV circulates.
Given the equivocal HeV titers in the 2 bats, these results are likely
false positives.
The findings indicate that NiV or an unidentified Nipah-like virus is
endemic in P. vampyrus in Indonesia. Further interpretation is
limited by the nonrandom sample, the <100% specificity of the VNT,
and the inability to corroborate serologic results by virus isolation
or polymerase chain reaction (tissue collection was not permitted by Indonesian
wildlife authorities).
Similar serologic findings are likely in overlapping P. vampyrus
populations and possible in overlapping populations of other Pteropus
species. Further research is needed to explain the geographic extent of
NiV infection in flying foxes and the nature and stability of the interface
between HeV and NiV, and to investigate the possible presence of other
cross-neutralizing henipaviruses.
Acknowledgments
We thank Biosecurity
Australia, the Department of Primary Industries and Fisheries, Queensland;
the Australian Animal Health Laboratory; the Research Institute for
Veterinary Science, Bogor, Indonesia; and the Indonesian Ministry of
Agriculture for facilitating this research. We also thank Tatty Syafriati,
Setyono, Herlin Dyah Sumaryani, Syamsul Bahri, Ir Maharadatunkamsi,
and Heri Nasution for help in the field and laboratory; Craig Smith
for equipment and logistic support; and Jonathan Lee for his valuable
experience-based advice.
We dedicate this
article to our colleague and friend David Banks, who died on May 7,
2005, in an aviation accident while returning from Cape York in northern
Australia after a field survey for quarantine pests and diseases.
Financial support
was provided by Biosecurity Australia and facilitated by David Banks.
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Suggested citation
for this article:
Sendow I, Field HE,
Curran J, Darminto, Morrissy C, Meehan G, et al. Henipavirus in Pteropus
vampyrus bats, Indonesia [letter]. Emerg Infect Dis [serial on the
Internet]. 2006 Apr [date cited]. Available from http://www.cdc.gov/ncidod/EID/vol12no04/05-1181.htm
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