Nigel Beebe, PhD
School of Biological Sciences
University of Queensland
St Lucia QLD 4072
Australia
P. xxxxxxxxxxxxxx
Fax. xxxxxxxxxxxxxxxxx
E. xxxxxxxxxx
31/07/14
RE: Submission to the Green Paper on developing northern Australia
As a scientist working on mosquitoes and mosquito-borne disease in the Australasian
region I am writing to highlight potential issues for consideration in terms of the
green paper, public health and biosecurity. While I can foresee potential solutions to
these issues through monitoring, management and community engagement, it is
imperative that these risks are highlighted with respect to the future development of
this region of Australia, public health and biosecurity and I have briefly detailed the
most important of these below.
1) Further establishment of permanent water storage in northern Australia is likely to
lead to the escalation of local and exotic mosquito-borne arbovirus activity.
Previous experience from the Ord River irrigation area would suggest that year-round
water storage may result in elevated freshwater endemic mosquito populations –
especially Australia’s most important freshwater arbovirus mosquito Culex
annulirostris. This mosquito is the major vector of several major local arboviruses
including Ross River fever, Murray Valley encephalitis and Kunjin (a subtype of
West Nile viruses (1), and capable of transmitting a North American strain of West
Nile Virus (2). Mosquito-borne disease studies around the Ord River Irrigation
System suggest storage of wet season waterflows can lead to the stabilisation of lake
margins that facilitate the growth of aquatic plant species leading to potential yearround mosquito populations and endemic arboviral activity such as Ross River,
Murray Valley encephalitis and Kunjin (3).
The mosquito Culex annulirostris was also responsible for the emergence of the
exotic Japanese encephalitis virus (JEV) in Papua New Guinea (PNG) and northern
Australia (4). This virus first appeared in the Torres Strait Islands in 1995 (three
human cases were reported on Badu Island, two of which were fatal (5). This exotic
virus is cycled through animals (“hosts”) including wading birds and pigs and the
expansion of permanent water storage in northern Australia is likely to increase the
co-occurrence of the mosquito (Cx. annulirostris) and the virus’s amplifying hosts.
This in turn is likely to increase the risk for exotic JEV activity establishing on
Australia’s mainland with risks to both public health and our agricultural animal
export industry – livestock and associated products would then require routine testing
to guarantee their freedom from infection.
One possible JEV incursion scenario could see the frequent movement of migratory
wading birds (or bats) arriving from the Torres Straits (or PNG) to access water and
subsequently introducing the virus (or perhaps other viruses) to these new wetlands
where both the mosquito and JEV amplifying hosts are already established and can
potentially cycle the virus.
2) The increase in population growth and urban development could drive the
emergence of dengue and chikungunya into these urban landscapes.
Dengue and chikungunya are two globally expanding arboviruses that can be
transmitted from human to human by two different mosquitoes – both of which can
exist and thrive in urban landscapes (i.e. small towns and cities). The first of these
mosquitoes, Aedes aegypti, is a tropical climate mosquito that currently exists in
Queensland and is already responsible for yearly dengue outbreaks in northern
Queensland usually initiated by international travellers who introduce the virus. The
dengue mosquito Aedes aegypti has twice invaded the Northern Territory town of
Tennant Creek from Queensland with the first incursion in 2002 requiring $1.5m and
two years’ control work to remove it from this town (population of only 3,100). The
eradication of the second incursion is still underway. The Asian tiger mosquito, Aedes
albopictus, can also transmit both dengue and chikungunya and arrived into the
Torres Straits from Indonesia in 1995 (6). Unlike the tropical dengue mosquito Ae.
aegypti, which can only survive in relatively warm climate urban landscapes, the
Asian tiger mosquito can exist in both urban and sylvan (or forested) landscapes in
both warm and cool climates (7). Increased urban development and human movement
via the proposed increased transport networks into and around northern Australia
urban centres is likely to result in these mosquitoes entering new urban landscapes
and thus increasing the risk of dengue and chikungunya transmission during summer.
One possible scenario would see a fly-in-fly-out worker arriving from a city where
these viruses are active (i.e. Cairns, domestically, or anywhere across the Asia-Pacific
region, internationally) and delivering the virus to an urban landscape where the
mosquitoes are already present. This could trigger an outbreak with local
transmission. While 133 people were diagnosed with chikungunya in Australia in
2013, these infections were all initially acquired overseas (8).
The expenditure associated with prevention of these two urban mosquitoes – clean up
of small incursions of these mosquitoes into urban landscapes detected through active
surveillance – far outweigh the huge cost of a disease outbreak and subsequent
removal of established urban populations of either of these two mosquitoes.
I would be pleased to provide a fully annotated and referenced report on these risks,
and any other information as required.
Yours sincerely,
Nigel Beebe
References
(1) Marshall, I. D. (ed.) 1988. Murray Valley and Kunjin encephalitis. CRC Press, Boca Raton, Florida.
(2) Jansen, C. C., C. E. Webb, J. A. Northill, S. A. Ritchie, R. C. Russell, and A. F. Van den Hurk.
(3) Liehne, C. G., N. F. Stanley, M. P. Alpers, S. Paul, P. F. Liehne, and K. H. Chan. 1976a. Ord River
arboviruses--serological epidemiology. Aust J Exp Biol Med Sci 54: 505-512.
Liehne, C. G., S. Leivers, N. F. Stanley, M. P. Alpers, S. Paul, P. F. Liehne, and K. H. Chan. 1976b.
Ord River arboviruses--isolations from mosquitoes. Aust J Exp Biol Med Sci 54: 499-504.
Liehne, P. F., N. F. Stanley, M. P. Alpers, and C. G. Liehne. 1976c. Ord River arboviruses--the study
site and mosquitoes. Aust J Exp Biol Med Sci 54: 487-497.
Liehne, P. F., S. Anderson, N. F. Stanley, C. G. Liehne, A. E. Wright, K. H. Chan, S. Leivers, D. K.
Britten, and N. P. Hamilton. 1981. Isolation of Murray Valley encephalitis virus and other arboviruses
in the Ord River Valley 1972-1976. Aust J Exp Biol Med Sci 59: 347-356.
(4) Hanna, J. N., S. A. Ritchie, D. A. Phillips, J. Shield, M. C. Bailey, J. S. Mackenzie, M. Poidinger,
B. J. McCall, and P. J. Mills. 1996. An outbreak of Japanese encephalitis in the Torres Strait, Australia,
1995. Medical Journal of Australia 165: 256-260.
Ritchie, S. A., D. Phillips, A. Broom, J. Mackenzie, M. Poidinger, and A. van den Hurk. 1997.
Isolation of Japanese encephalitis virus from Culex annulirostris in Australia. American Journal of
Tropical Medicine and Hygiene 56: 80-84.
van den Hurk, A. F., D. J. Nisbet, R. A. Hall, B. H. Kay, J. S. Mackenzie, and S. A. Ritchie. 2003.
Vector competence of Australian mosquitoes (Diptera: Culicidae) for Japanese encephalitis virus.
Journal of Medical Entomology 40: 82-90.
(5) Mackenzie, J. S., C. A. Johansen, S. A. Ritchie, A. F. van den Hurk, and R. A. Hall. 2002. The
emergence and spread of Japanese encephalitis virus in Australasia. Current Topics In Microbiology
and Immunology 267: 49-73.
(6) Beebe, N. W., L. Ambrose, L. A. Hill, J. B. Davis, G. Hapgood, R. D. Cooper, R. C. Russell, S. A.
Ritchie, L. J. Reimer, N. F. Lobo, D. Syafruddin, and A. F. van den Hurk. 2013. Tracing the Tiger:
Population Genetics Provides Valuable Insights into the Aedes (Stegomyia) albopictus Invasion of the
Australasian Region. PLoS neglected tropical diseases 7: e2361.
(7) Hill, M. P., J. k. Axford, and A. A. Hoffmann. 2013. Predicting the spread of Aedes albopictus in
Australia under current and future climates: Multiple approaches and datasets to incorporate potential
evolutionary divergence. Austral Ecology DOI: 10.1111/aec.12105.
(8) Australian Government Department of Health. Disease notifications from 1991 to 2013
http://www9.health.gov.au/cda/source/rpt_2.cfm
.