Fortunately and largely because of its geographic isolation, Australia's
livestock remains free of all major epidemic diseases and relatively free of
other serious pests and diseases. Australia also has a sound quarantine regime
in place. The 2008 review of Australia's quarantine and biosecurity
arrangements (the Beale Report) concluded that Australia operates a good system
that is 'often the envy of other countries given its comprehensiveness, transparency,
and scientific rigour'.
Even so, it recognised that improvements could be made to the arrangements with
the aim of achieving 'a seamless biosecurity system that fully involves all the
appropriate players...across pre-border, border and post-border risk management
Although this review did not deal specifically with the Torres Strait, its
findings have direct relevance for the region.
Biosecurity is a critical aspect of conservation in the Torres Strait
and the Treaty recognises this importance. As noted in chapter 2, Australia and
PNG have undertaken to prevent the entry or establishment of species of fauna
and flora that may threaten the health of indigenous animal and plant life. In
this chapter, the committee identifies the main challenges facing the region
from the introduction and spread of harmful weeds, pests and diseases. It also
looks at the risk of damage to the environment from the release of toxic or
harmful substances from vessels passing through the strait.
Biosecurity in Torres Strait
The proximity of the Torres Strait Islands to Australia's near northern
neighbours, such as PNG, is one of the region's key biosecurity concerns. Less
than five kilometres separates the northern-most island, Saibai, from the PNG
coastline, with the remaining islands and reefs scattered throughout the region,
forming stepping stones that provide an ideal route for the entry of harmful
diseases or pests.
The concern with the introduction of exotic diseases, pests or weeds is not so
much coming from Australia northward to PNG but rather the converse.
There are several exotic pests and diseases of major concern to
Australia that lurk on Australia's northern doorstep, including the screw worm
fly (SWF), Asian tiger mosquito, papaya fruit fly and Japanese encephalitis
(JE). Classical swine fever, which is a very serious exotic disease of pigs, is
another. It has moved into West Papua and, according to Dr Andrew Carroll,
Chief Veterinary Officer, DAFF, is 'likely, slowly but surely, to move across
into PNG at some time'.
These pests and diseases can be transmitted through human-assisted movement
and natural dispersal. In the following section, the committee examines the
potential for harmful pests or diseases to spread to the Torres Strait and the threat
they pose to humans, livestock and the environment.
Under the terms of the Treaty, Australia is required to permit free
movement of traditional inhabitants who are undertaking lawful traditional
activities in and in the vicinity of the Protected Zone. The presence in PNG of
noxious pests and diseases not found in Australia coupled with the free
movement provisions creates a significant risk to Australia's biosecurity.
Because humans or their companion animals are potential carriers of
disease or pests, this flow of traditional inhabitants complicates the
management of biosecurity in the Torres Strait.
The committee has referred to PNG nationals crossing the border to seek medical
assistance. Clearly, they pose a considerable risk of spreading infectious
diseases such as tuberculosis. But any person visiting the Torres Strait from
PNG to attend gatherings, hunt or trade could carry with them an exotic plant,
pest or disease and inadvertently introduce them into the region. People who
endeavour to gain entry illegally create a particular problem for biosecurity
because their intention is to avoid detection.
The screw worm fly (SWF), an insect parasite of warm-blooded animals, is
an example of a pest likely to be brought into the Torres Strait. This insect
is considered to be the most exotic pest threatening Australia's livestock
industries and is endemic in a number of Australia's northern neighbours,
including PNG's coastal swamps adjacent to the Torres Strait.
Dogs and humans are susceptible hosts of SWF. One study found that:
...companion animals, especially dogs, aboard illegal vessels
represent a risk for the introduction of SWF larvae if the origin of the vessel
is a SWF-endemic country. Introduction of the disease through the Torres Strait
into the mainland of Australia may also be possible via the legal importation
of companion animals if these animals are not examined appropriately before
entering the mainland.
According to the Australian Veterinary Emergency Plan, should this pest
reach Australia it would 'have disastrous effects on the cattle industry unless
There are similar issues with regard to plant pests and disease being
carried into the region by humans.
Pests that are prevalent in PNG, such as the red-banded mango caterpillar and
the papaya fruit fly, have been detected in the Torres Strait and require
constant monitoring to contain any further incursions.
For example, the number of papaya fruit flies detected in the Torres Strait is
'extremely high', with routine inspections finding 309 in 1995; 1,156 in 1998; 456
in 1999, 113 in 2001 and 118 in 2002.
It was first found in the Torres Strait in 1993 on Saibai, Boigu, Dauan,
Stephen and Darnley Islands. A pest infestation can result in substantial
losses in production, restrict market access and damage the environment.
Commonly known as the climbing perch, Anabas testudineus is
another example of a pest introduced by humans, in this case by Indonesian
villagers. Dr Lawrence explained that people have dumped it in swamps and other
places and it has migrated down the Fly River into the Fly estuary in PNG. He
explained that although a nice fish to eat, it is a threat to bigger fish such
as the barramundi that choke on its spines. According to Dr Hitchcock, that
species is now found on Saibai and Boigu in the Torres Strait.
Because of the high level of shipping traffic through the
straits—recreational, commercial, indigenous and illegal fishing vessels—the
region is also at risk from ships introducing invasive marine species. Some
species of marine pests such as the Striped Barnacle and Upright Moss Animal
can travel long distances as a fouler on ships' hulls. Their presence has been
recorded in the Torres Strait. Pests can also be introduced through contaminated
As shown in the illustration opposite, the activity of foreign vessels
in the Strait may result in the introduction of weeds, pests or disease harmful
to plant, animal or human health in the region.
The transmission of human diseases such as dengue fever is another major
biosecurity concern in the Torres Strait. A patient with dengue can transmit
the virus to mosquitoes that may then infect other people. According to
Queensland's management plan for dengue fever, 'It only takes one imported case
of dengue to start an outbreak'. It explained:
Because dengue is not endemic to Australia, local dengue
outbreaks in Northern Queensland all begin with a single imported case—a
For example, the outbreak in 1996–97 started with one person returning
to Mer after contracting the disease in Daru. The management plan noted:
Because of high Ae. aegypti populations on Mer, this
one case led to a further 70 cases on the island. Subsequent travel of viraemic
patients between the islands led to infections on at least six other islands in
the Torres Strait. Within seven months, 201 cases were confirmed, reaching
locations as far south as Townsville.
People and accompanying animals are not the only means by
which noxious weeds and exotic pests and diseases find their way into the
Torres Strait and then onto mainland Australia. Dr Andrew Carroll, DAFF,
explained that there are many ways that things can come across from PNG besides
the more commercial movements assisted by people: they can 'also float across,
blow across, fly across and swim across'.
Figure 11.1: Quarantine poster—risks from illegal fishing vessels
(Image courtesy of Department of Agriculture,
Fisheries and Forestry)
DAFF explained that the prevailing climatic and environmental conditions
can 'facilitate the unassisted movement of risk organisms through natural
pathways including seasonal wind and tidal actions and migratory bird movements'.
Papaya fruit fly, for example, may not only be carried across the border in
plant material but can be blown from the mainland to the islands. 
The movement of nomadic waterfowl between northern Australia and PNG has
been identified as 'a potential route for the introduction of avian influenza (AI)
(and other disease agents) into Australia'. With islands located so close to
PNG and hundreds and thousands of birds moving back and forth across the strait
each year, it is 'the major bio-security threat for Australia' and 'the obvious
pathway of any disease like bird flu moving into the country'.
Thus, there is an ever-present risk of the transmission of AI through infected
Also, Ms Morris informed the committee that there has been 'a movement
of a number of vectors into the Torres Strait and increased concern associated
with the prevalence of new vectors and pests—fish and the like—that they have
not seen there before'.
One particular area of interest is mosquitoes, particularly the Aedes
albopictus, commonly known as the 'Asian Tiger mosquito'. This mosquito is a
potential vector of flaviviruses, including dengue and chikungunya, and
Australian viruses such as Ross River virus and Barmah Forest virus.
As noted above, the dengue virus is not endemic to Northern
Queensland but arrives via a human reservoir from outside the region. The
disease is vectored by the dengue mosquito, an exotic but very human-associated
species. According to DoHA, there have been repeated
incursions of the Asian Tiger mosquito in past years.
This mosquito, which is very aggressive, outcompetes the dengue mosquito and, although
a poorer vector of dengue, feeds on more hosts and can transmit many more
While not currently established in Australia, it presents a serious risk of spreading
to the Torres Strait.
Another disease, Japanese encephalitis (JE), is endemic to PNG. This
potentially fatal disease is caused by the JE virus and is spread by the bite
of an infected mosquito. Pigs, which are particularly good hosts, and wild
birds have an important role as hosts in the spread of the virus.
Mosquitoes feeding on infected pigs are likely to pick up the virus and may then
transmit it to humans.
In 1995, JE first appeared in the Torres Strait on Badu. During the next couple
of years, the virus recurred in the north of the Torres Strait, with a
significant outbreak in 1998, when for the first time, the virus was detected
further south in Cape York. Scientists were able to show that the virus found
in Western Province, PNG, was genetically the same as the virus in Australia.
According to a researcher:
We think it [the virus] island-hopped, with localised
transmission cycles between birds and mosquitoes—or perhaps pigs and
mosquitoes—on each island, as it moved through the Indonesian archipelago,
finally coming to Papua New Guinea and then down to the Torres Strait.
The concern now is that the virus will spread and become established
In 2002, the virus was detected on Darnley soon after being found on Badu. At
that time, the Northern Australia Quarantine Strategy (NAQS) noted that the end
of the monsoon season and climatic conditions are perfect for an influx of
JE-infected mosquitoes, blown south from PNG.
The varroa mite, a highly invasive parasite that feeds on the blood of
adult and larval honey bees, also poses a significant threat to Australian
agriculture. According to Dr Carrol, DAFF, 'recent developments with varroa in
PNG are of considerable concern, because varroa would be a serious pest for our
These mites can establish themselves in other colonies by, for example,
hitchhiking on an infected bee or through the activities of bee-keepers acting
as agents, including through the use of contaminated equipment.
The committee has not identified all the weeds, pests or diseases
present in PNG or Indonesia that have the potential to enter Australian
territory through the Torres Strait and cause significant damage to sectors of Australia's
farming industry, to the environment and to human health. According to an
Animal Health Australia spokesperson 'it only takes one serious disease or pest
to slip through to significantly disrupt our accepted way of life in Australia'.
Such infestation could result in the widespread destruction of plant and animal
life and the cost of eradication could amount to millions of dollars.
Pests like fire ant, and
invasive weeds, have already cost the nation dearly in foregone revenue and
Although the committee noted only a few examples of pest or disease
intrusion into the region, the threat of such incursions is ever present and
could be increasing.
According to Dr Carroll, the risks of harmful exotic weeds, pests and
diseases entering the Torres Strait are generally rising due to more trade and other
activities involving the movement of people. He explained:
There was an outbreak last year or the year before of a very
virulent form of newcastle disease up on the top of Papua New Guinea that had
been brought in by, we believe, loggers coming in and bringing their fighting
cocks with them...Also there are the risks coming across from Indonesia into
Indonesian Papua and then moving across as more settlement develops there.
Things like the big gas pipeline and various mining activities will mean a lot
of mining equipment comes in. Unless great care is taken, that will introduce a
whole range of soil-borne pests, particularly plant pests, and also hitchhiker
pests—insects et cetera. So the risk in general, yes, is increasing.
Dr Garrick Hitchcock, an anthropologist who has worked on both sides of
the border, also referred to population trends in PNG and likely implications
for the Torres Strait. He said:
It is clear that a key issue for the region is Papua New
Guinea’s rapidly expanding population, which will have a profound impact on the
future of Torres Strait, as more and more Western Province people use the
waters for subsistence and cash-producing activities, and visit the Australian
islands to access their infinitely better health and other services. When I
commenced research at Bensbach in 1995, none of the locals had ever been to Torres
Strait; more recently, it is quite common for sick and injured villagers to
make the long journey to Boigu Island’s clinic.
Although his main concern was with health problems due to increased
numbers of PNG nationals visiting the region, his suggestion of increased
subsistence and cash-producing activities in Western Province could have
significant biosecurity consequences for the Torres Strait.
The 2008 independent review of Australia's quarantine and biosecurity
noted that the challenges from climate change were an emerging risk for
Australia. It referred to an increased potential for pest and disease
incursions as the number of viable natural pathways for exotic pests and
Ms Morris explained that the problems associated with rising sea levels 'will
become more acute because of the inundation and because of the difficulties in
habitation and then for straight-out biosecurity and security reasons'.
Scientists have suggested that the life cycle of organisms in the region
is likely to be influenced because of changes in climate. For example, CSIRO's research
indicated that the main biosecurity threat to the Torres Strait Islands comes
from climate change and the associated southern movement of key disease-vectoring
mosquitoes from PNG and their potential to increase disease type and incidence.
Dr Andy Sheppard, CSIRO, explained that the insects are very sensitive to small
environmental changes, so their ability 'to survive and also transmit the
diseases will be heavily temperature dependent'. In his opinion, climate data
is a key variable that is going to change the impact or the virulence of this
According to Dr Sheppard, mosquitoes have expanded from PNG since about
2004 to most Torres Strait Islands, which may be linked to climate change.
He could not make a general observation about the risks of exposure as a result
of the easy vectoring of diseases in the north because the research was 'very
much ongoing'. Although scientists do not have a definitive answer yet, he suggested
that if the predictions of those models were realised then, potentially, they would
have quite a serious impact on the risks to which people are exposed in the region.
He noted further that while the broadly predicted changes in climate could have
'a significant impact', the predictive capacity is 'hampered by a lack of
high-quality observational data'.
In fact, he explained that, because of a perceived level of increased risk, research
started only about 12 to 18 months ago. He informed the committee:
So, while we believe the risk is on the increase, we have not
been able to take it to the point where we can actually define how it might
impact the local community. One reason we cannot do that is because there is a
lack of detailed localised climate data that allows us to do climate modelling
around the biology of the vector and the interaction between the vector and
humans. We have these clear observations that the mosquitoes are on the move
and we know about the biology and the interactions between mosquitoes as to how
that might change the impact on the diseases, but I am afraid at the moment the
rest is rather speculative and it really is dependent upon us having better
data for some good biological modelling.
In summary, he stated:
It is a very complex question because it is not just a
question of the impact of the climate change or increasing temperatures on the
mosquito populations. It is also about that interaction between the mosquitoes
and their ability to transmit the viruses. That is why we have started this
research. It is to really bring the virologists and the entomologists back together
to better understand the system.
As noted earlier, changes in climate may affect the life cycle of a
range of organisms, and not just mosquitoes. For example, climatic conditions
and other physical factors determine the potential for the SWF to survive and
increase in number in a geographic area.
In the committee's view, there is a clear need for a comprehensive study of
changes in climate and their implications for the Torres Strait as a single but
complex ecosystem in the short and long term.
A number of exotic weeds, pests or diseases are present in Australia's
near northern neighbours that, if introduced into Australia, could cause
significant harm to people, animals, plants and other aspects of Australia's
unique environment. As the main gateway through which such threats may enter
Australia, the Torres Strait is a major biosecurity concern for the country.
The region's isolation, low-density and dispersed population, proximity to an
international border, geography and climate generate significant challenges for
Australia's biosecurity. The free movement of local inhabitants allowed under
the Treaty, projected population increase in PNG's Western Province, illegal
activities, especially by unauthorised fishers, and climate change add to the
difficulties facing those responsible for Australia's biosecurity in the Torres
Strait. The following chapter considers how Australia attempts to manage the
numerous biosecurity threats that exist in the region.
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