Seafood imports and potential disease pathways
The committee's interim report provided information on WSSV, including
its virulency, hosts and the ways in which the virus can be transmitted.
As the inquiry continued, the committee heard evidence regarding the possible
pathways by which WSSV may have entered the country, and therefore how the WSD
outbreak occurred in Queensland.
Since the outbreak of WSD in the Logan River prawn farms, there has been
ongoing discussion and speculation as to how the white spot virus may have
entered Australia, given it is an exotic disease to the country. As many of the
countries that import seafood product into Australia have white spot in their
prawn populations, importation has received significant attention as a possible
This chapter considers importation and other possible pathways that may
have introduced white spot into Australian prawn populations, including five
pathways specifically being considered by DAWR. There is also discussion of
biosecurity failures that may have led to white spot entering Australia.
Genetic testing may provide information as to the origin of the recent
WSD outbreak. The findings to date of genetic testing are presented in this
Five possible pathways
DAWR advised the committee that it was considering five possible
pathways that may have led to the introduction of WSSV into Australia. The
pathways being considered for the entry of WSSV into Australia are:
that the virus could have already been present in Australia without
via imported aquatic feed or feed supplements;
via diseased broodstock or their progeny;
through a human element, including the importation
of associated equipment; or
via raw imported prawns being used as bait.
Further, in a report from May 2017, DAWR submitted that the spread of
WSD could be attributed to a number of factors including 'common water
exposure, movement by wild animals and birds, sharing of equipment and common
production inputs', as well as water run-off and oral transmission (for
example, prawns and crabs eating infected species).
However, DAWR considered that the risks associated with vessel ballast
water and biofouling as pathways for the introduction of WSSV to Australia were
'very low to negligible', especially in light of ballast water management
practices implemented from 2001.
As of 11 September 2017, DAWR had yet to determine a definitive cause of
the outbreak, and was continuing to examine the variety of possible pathways.
It was also continuing genetic testing to identify any link between the
infected prawns and overseas strains of the white spot virus.
Pathway 1: Present in Australia
without prior detection
The committee heard some evidence that, despite no clear detection, WSSV
may have been present in wild seafood populations in Australia for some time at
very low levels, prior to the 2016 incursion. Therefore, this may have been a
pathway to the WSD outbreak.
In response to questioning from the committee, DAWR advised that as part
of the development of the 2009 IRA, the department considered whether white
spot could establish and maintain itself in the wild. Dr Andrew Cupit of DAWR
acknowledged that there was 'every possibility' that white spot may not be able
to maintain itself in the wild, and noted that in the wild, the disease would
also be subject to natural predators. DAWR noted that it had now established
surveillance in wild prawn populations to try and more definitively ascertain
the likelihood of this pathway.
Dr Patrick Hone of the FRDC noted that there was a low probability that
the disease had existed undetected in the wild, prior to the outbreak. Dr Hone
stated that if it had been present in the wild for some time, there would have
been 'so many opportunities for it to express itself as a disease, through
either farms or other avenues, that we would have probably seen some mortality
This position was also put forward by Dr Ben Diggles, who argued that
this was one of the least likely pathways, 'as if this were true, WSSV
outbreaks would have been observed on the Logan River and elsewhere before
DAWR additionally noted that until genetic testing on WSSV in Australia
was completed, it was not possible to draw any conclusions about the origin of
the outbreak or the period of time it may have been present in Australia.
Pathway 2: Aquatic feed or feed
It was suggested that prawn feeds and associated products could be the
source of WSSV entering Australia.
The Ridley Corporation provides approximately 80 per cent of
the prawn feed market in Australia. The Ridley Corporation provided evidence
that WSSV is highly heat sensitive, with heat treatments shown to kill the
virus. The Ridley Corporation advised that 'heat treatment has been validated
globally on many occasions as a standard means of deactivation of white spot
virus and other pathogens in feed and other biological materials including
The Ridley Corporation advised that the OIE considers that white spot is
destroyed by heating it to 60 degrees Celsius for one minute, or 70 degrees
Celsius for 0.2 minutes. In response to claims that white spot may have
entered Australia via infected prawn feed, Dr Richard Smullen of Ridley
Corporation advised the committee that:
All our feed is heat treated
to between 85 and 110 degrees for 45 minutes. All our marine raw materials that
are imported are also heat treated to a very high level. We also, just to be
100 per cent sure, do not use any farmed crustacean material in our feeds. Although,
there is evidence that, even if farmed prawns that have white spot have been
put into feed experimentally and then the feed made using the normal process,
it is not possible to transfer that disease to the prawns.
Dr Smullen argued that as Ridley feed product was distributed throughout
Australia and overseas, and no other prawn farms developed white spot, the
recent disease outbreak could not be attributed to prawn feed. If feed did
transfer WSSV, it would be expected that all farms in Australia would be
infected with WSD. Similarly, as feed is distributed across all prawn ponds on
a farm simultaneously, it would be expected that an outbreak would likewise
occur in all ponds simultaneously, and this was not the case in the Logan River
In testing the feed used on the farms, DAWR found that WSSV DNA
fragments were present in prawn feed pellets produced by one feed supplier.
However, the DNA was fragmented due to heat treatments and other manufacturing
processes, rendering the virus unviable. DAWR noted that feed, additives and
similar products should be treated, stored and transported appropriately to
reduce the risk of disease.
However, DAWR did not rule out this pathway as being responsible for the
Logan River outbreak, and argued that:
the illegal transport and use of these products has been
known to occur and cannot be ruled out. This is because samples and small
quantities of products can be easily moved between countries and it can be
difficult for regulatory authorities to detect. Previous investigations
conducted by the department uncovered hatchery feed products being illegally
imported into Australia. The companies responsible were prosecuted. Illegally
imported feed represents a high risk pathway for WSSV and cannot be ruled out as
a possible pathway for the Logan River area outbreak.
Pathway 3: Diseased broodstock
For prawn farms to begin production each year, they require ponds to be
stocked with juvenile prawns, known as 'post larvae' (PLs). PLs are produced in
hatcheries from adult, broodstock prawns. Farmers may either run their own
hatcheries, or purchase PLs from other farms or commercial hatcheries. Of the
Logan River prawn farms infected, three also operated hatcheries to produce PLs
to stock their farms.
DAWR advised that broodstock used by the hatcheries were sourced from
wild caught stock sourced from Australia's northern prawn fishery waters. When 10 per cent
of these wild‑caught prawns were tested for WSSV as part of standard screening
processes, the virus was not detected. However, DAWR warned that the
'collection of wild broodstock to produce PLs for domestic grow out purposes is
not recommended industry practice for biosecurity reasons', and warned that the
remaining 90 per cent of product was not tested.
Given that all farms outside the Logan River area that received PLs
remained uninfected with white spot, it was suggested by DAWR that PLs might
not be the source of the outbreak. However, as broodstock and PLs 'represent
the most direct pathway for entry, exposure, vertical transmission of disease,
establishment and spread of disease', it could not be discounted as the
original source of the infection.
However, Dr Diggles argued that broodstock being the cause of the WSD
outbreak was 'extremely unlikely', as a number of prawn farms outside the Logan
River area had been supplied with hatchery stock from a Logan River farm, and
remained negative for WSSV. Additionally, the prawn farms along the Logan River
obtained PLs from different sources.
In his March 2017 report, Dr Len Stephens argued that the reliance on
wild caught, rather than farmed broodstock was now an 'unacceptable risk for
the industry'. Dr Stephens noted that in relation to wild broodstock,
'extensive testing of broodstock for WSD and other diseases is essential to
prevent disease entering production farms and nurseries'.
Pathway 4: Human activity and
DAWR investigations into the potential pathways of the white spot
outbreak included the virus being introduced into Australia via infected farming
equipment or direct human intervention.
Dr R Parry Monckton, of Monckton Consulting, argued that the use of
contaminated equipment was a significant transmission route between prawn ponds
and hatcheries, as was the movement of people in and out of prawn farming
facilities. Dr Monckton stated that modern prawn facilities have 'rigid
biosecurity protocols to prevent any uncontrolled people movement', but some
Australian prawn farm facilities did not appear to have such biosecurity
A similar argument was put forward by DAWR. DAWR submitted that its
investigations had found that:
on most farms, on-farm biosecurity for movement control of
people and equipment was below international best practice. On some farms it
was non-existent, and no evidence could be collected that demonstrated
visitation or biosecurity measures. On enquiry, farm staff confirmed that some
equipment is shared between farms, for example, prawns from other farms are
cooked on their premises to share processing equipment. Farm staff also
confirmed that their farms are visited by peripheral industry representatives
including feed manufacturers, equipment salesmen, production consultants and
various sales representatives from Australia and overseas.
Overall, DAWR's investigations found no evidence that contaminated
equipment or direct human involvement introduced the disease to the Logan River
area. The disease was 'unlikely to remain viable on dry equipment or clothing'.
However, DAWR noted that some prawn farms had hosted two foreign
visitors on 25 November 2016, three days after the first signs of WSD on the
first infected property. While not considered significant to its
investigations, DAWR stated that it was continuing its enquiries in this area.
In response to the claim that overseas visitors may have brought white
spot into the country, the APFA argued that it was 'disingenuous to put this
forward as a genuine line of inquiry'. The APFA noted that it had not observed
any behaviour that would support the position that overseas visitors had 'any
possible involvement in the WSSV incursion'.
Pathway 5: Imported raw prawns used
As highlighted in the committee's interim report, a number of witnesses
submitted that imported infected raw prawns, intended for human consumption,
were the cause of the outbreak. It was argued that infected raw prawns that
were used as bait in the Logan River introduced the disease to those waterways
used by prawn farmers.
As part of its investigations, in December 2016 DAWR officers visited a
number of sites along the Logan River commonly used by anglers to determine if
raw prawns were being used as bait in the river. Two recreational fishermen
were found to be fishing with raw imported vannamei prawns, intended for human
consumption. The prawns being used as bait were tested for WSSV, returning
positive results from multiple laboratories. DAWR stated that:
The fishermen admitted that this was the third occasion that
they had fished in the river using prawns for human consumption but claimed
they were unaware that prawns of this nature should not be used as bait. The
prawns used by the fishermen on this occasion were from a bag that was labelled
'for human consumption'.
In January 2017, DAWR conducted further surveys of fishermen on the
Logan River, and found that out of 144 anglers interviewed, nine reported using
raw prawns intended for human consumption as bait. DAWR concluded that:
it is evident that some raw imported prawns recovered from
retail outlets proximal to the infected properties tested positive to WSSV. It
is also known that to some extent these WSSV infected prawns are used by
fishermen in the river and also discarded or fed to birds following the fishing
activity. Using prawns as bait for fish represents a possible entry and
exposure pathway for susceptible crustaceans.
DAWR's findings were supported by evidence in other reports about the
outbreak. In a February 2017 report, Dr Diggles noted that the major risk
factor for farm infection 'appeared to be water intake from the [Logan] River
or Moreton Bay'. Dr Diggles presented evidence that infected bait in the
waterways was a plausible pathway, arguing that:
the epidemiology and chronology of disease spread together
with evidence of significant recreational fishing effort in and adjacent to the
intake canal at [the first infected farm], strongly suggests, in my
professional opinion, that the incursion pathway was most likely introduction
of WSSV via the [first infected property] intake canal. Indeed, surveys by
Fisheries officers allegedly found several groups of recreational fishers using
imported green prawns as bait within 500 meters of the intake of [the third
infected farm], and of these 33% of bait samples were positive for WSSV. This
pathway is plausible given evidence that; 1. Increasing numbers of recreational
fishers are using imported prawns as bait, and 2. Biosecurity breakdowns at the
international border resulting in c. 50-54% of imported green prawns sold at
the retail counter being WSSV positive in the leadup to Christmas/New Year
Dr Diggles therefore concluded that 'there is a strong possibility that
the disease incursions in the Logan River and Moreton Bay were caused by use of
imported uncooked prawns as bait or burley by recreational anglers'. Dr Diggles
reinforced this view by stating that it was unlikely that the WSSV disease
pathway was via ballast water discharge, biofouling of shipping, infected
broodstock prawns, or aquaculture feed.
Dr Diggles argued that the intake canals for prawn farms have limited
water exchange and are accessed by large numbers of potential disease hosts
such as prawns, crabs and plankton. Given the semi-isolated nature of the
canals, they are 'perfect for establishment of WSSV infection in wild reservoir
hosts and vectors'.
The APFA drew on the findings of Dr Diggles and presented its view that
the outbreak of WSD was most likely due to the importation of raw prawns infected
with WSSV, subsequently used as bait in the Logan River.
The committee put to QDAF the possibility that the virus was building up
in the Logan River as a result of contaminated bait being used in its waters.
Contaminated river water would then be drawn into the first prawn farm, noting
that in most instances of infection, the first pond infected was the first to
be filled by river water. The virus would then concentrate in the pond, be
released back into the river, where the same activity at the next farm would
further concentrate the virus prior to re‑release into the river. QDAF
considered this to be a 'plausible pathway'.
Mr Ian Rossmann, of the GI Rural prawn farm, has publicly stated his
view that the infection was a result of imported prawn product, and that the
infection took hold in the Logan River. Mr Rossmann told media that:
I'm very confident it came from the [Logan] River, we pump
water into the farm from the river and tests have shown it is positive in the
river...We have been very concerned about white spot introduction into Australia
through green prawn imports and we believe 100 per cent that that is where
it came from. Anyone who purchases a green prawn from overseas from a white
spot infected country, that can get into our waterways by bait, crab bait or
even just throwing it into the water.
SIAA expressed its 'amazement' that recreational fishers and the general
public were able to achieve such close proximity to the Logan River prawn
farms, 'when the biosecurity risk was so well known to industry and State
government regulators'. SIAA argued that closing this pathway would be very
effective in blocking a disease incursion from this source.
Regulating bait usage
The IRA provides that labelling imported prawns as 'for human consumption
only' and 'not to be used as bait or feed for aquatic animals' may reduce the
likelihood of WSSV exposure to the environment. However, the IRA goes on to
state that 'as this labelling would not necessary apply at retail sale, the
general public may be unaware of this requirement' and therefore by itself,
this labelling was 'not considered likely to reduce the overall risk to an
Supporting this view, the committee heard concerns that there was a lack
of education in the recreational fishing and broader retail market about the
implications of using raw imported prawns for bait. This included removing
marinade coverings from raw prawns so that they could be used as bait.
In his submission to the inquiry, Dr Diggles observed that in visiting
retail outlets over the Christmas period in 2016-17, 'not one of them were
selling imported prawns over the delicatessen counter with warnings to
customers that they should not be used as bait'. Further, some outlets had
placed bait freezers in close proximity to the seafood section, 'encouraging
consumers to relate the two together'.
The committee was concerned by evidence suggesting that in some forums,
fishing industry participants were encouraging the use of raw supermarket
prawns intended for human consumption as bait. In these forums it was argued
that these raw prawns were cheaper than prawns sold specifically for bait usage.
The committee queried whether there was capacity to place restrictions
on bait usage, particularly in the Logan River area. In response, prawn farmers
indicated that this would be a very difficult task. Ms Serena Zipf of the Rocky
Point Prawn Farm stated that, even after fishing activities were banned around
the farm's property following the WSD outbreak, recreational fishers continued
to fish in quarantined areas and 'in our channels with imported bait'.
With regards to bait use restrictions, Ms Zipf also noted that:
the rule is only as good as
the policing effort that you are prepared to put behind it. We could spend all
weekend policing our channels and we would not catch every fisherman who was
trespassing on our properties with bait which should not be used as such. So
the answer is it is impossible to police.
This position was supported by QDAF, who advised that it was very
challenging to enforce bait use restrictions, and would require compliance or
enforcement officers to prove that raw prawns being used as bait were not local
prawns. Additionally, QDAF argued that educational campaigns were challenging, and
noted that the decision to use raw prawns intended for human consumption as
bait was often driven by price.
Mr Eric Perez of QSIA argued that it was 'almost an impossibility' to
control how seafood bought at a retail level was used. Mr Perez went on to state
Once imported, seafood has
been sold at the retail level. You cannot control its use or where and when it
is used. We do not know how you could do that. Obviously risk reduction in the
seafood supply chain must be applied before retail or at the retail counter.
Once it is sold, it is too late, and you will never educate the masses that a
seafood product that is safe to eat is not safe to use as bait.
The NSIA supported this view, stating that the only proper way to
control risk in the supply chain was pre-border or at the border. NSIA argued
that once imported seafood products 'clear quarantine, and are sold across the
retail counter, all control of the end use is lost'.
GSDA argued that imported prawn products should be accompanied by a
statement, declaring that it is illegal for the prawns to be used as bait. Such
a statement should be included regardless of the type of processing or
packaging of the prawns. GSDA also called for the development of an easily
identifiable packaging logo to emphasise the risk.
In March 2017, the NSW Minister for Primary Industries, the Hon Niall
Blair, called for a 'national co-ordinated strategy to educate stakeholders' on
movement control orders and the biosecurity risks associated with using raw
prawns as bait. Minister Blair noted that NSW had tested over 17 000 wild prawn
samples as part of an ongoing surveillance program. NSW would also 'contribute
funding towards a multi‑media campaign to ensure everyone in the fishing
community is aware of the risks [of white spot]'.
On-farm biosecurity practices
During the course of the inquiry, evidence was submitted to suggest that
poor on‑farm biosecurity practices at prawn farms were a potential cause
of the WSD outbreak, or that Australian prawn farms were not appropriately
equipped to deal with disease incursions.
As part of its report into the cause of the 2016 WSD outbreak, DAWR
noted that effective on‑farm biosecurity management and practices were
necessary to reduce the risk of pest and disease incursions. In relation to the
Logan River prawn farms, DAWR stated that:
The production and biosecurity practices of each infected
premises were observed, highlighting not only the differences across the seven
infected premises but also the standard exhibited on the Logan River properties
compared with the farming and biosecurity techniques recommended for use in
modern prawn farming operations. There were few biosecurity infrastructure
and/or practices in place capable of preventing the disease transmission (apart
from some water filtering, pond fallowing and probiotic use), which is in stark
contrast to modern-day farming techniques and the biosecurity practices that
are put in place to prevent disease outbreak.
DAWR further argued that poor on‑farm biosecurity measures on some
farms may have contributed to the WSD outbreak or in the spread of the disease.
DAWR called for prawn farms to implement effective biosecurity measures,
including appropriate strategies for crab and bird mitigation (as both animals
can play a role in spreading WSSV), and water filtration.
SIAA suggested that the prawn farms on the Logan River had not invested
appropriately in biosecurity infrastructure, including closed water systems.
Further, management systems were required on the farms to prevent and manage
serious disease events. SIAA noted that these statements were 'consistent with
advice given to the prawn farmers by biosecurity experts advising them on
recovery and future phases'.
SIAA called for all stakeholders to consider the location, design and
management of prawn farms, given that intensive prawn farming can escalate
exotic diseases from low prevalence to an epidemic, which can then spread to
the environment. SIAA encouraged Australian prawn farms to implement the same
biosecurity standards of many prawn farms that it had observed overseas, where
WSSV is endemic but effectively managed.
The ACPF acknowledged that intensive prawn farming is a known disease
vector and that 'proximity of prawn farms to wild prawn populations requires
careful biosecurity management by prawn farming businesses'. The ACPF supported
calls for prawn farms to use new infrastructure and better practices to improve
In response to claims of poor on‑farm biosecurity practices, Mr
Alistair Dick, Gold Coast Marine Aquaculture, argued that this line of inquiry
'fails to recognise the extreme lengths that people need to go to to protect
themselves against white spot', and that such processes would not be entered
into lightly. Mr Dick stated that the argument of poor farming practices was viewed
as 'quite offensive' by the prawn farming industry.
This position was also put forward by Ms Serena Zipf of the Rocky Point
Prawn Farm, who stated that:
that exact phrase, 'poor
on-farm biosecurity', was in fact the subject of a press release by DAWR the
day after the prawn farmers left Canberra after we met with the department. We
obviously did not take very kindly to the timing of that press release or the
insinuation contained in the release.
The prawn farmers expressed their concern to the committee that
reporting on the outbreak had, intentionally or otherwise, placed blame for the
outbreak on farming practices. Farmers felt that media had reported on the
progress of the virus among the farms and may not have given sufficient
consideration to the role of the river in spreading the infection, and thus for
the farms 'the stigma was there right from the word go'.
Both the Queensland and federal biosecurity departments are undertaking
genetic testing on the white spot virus responsible for the outbreak in the
Logan River in 2016.
In a submission to the inquiry, Associate Professor Wayne Knibb advised
of genetic testing on WSSV being completed by the University of the Sunshine
Coast (USC), Queensland. Associate Professor Knibb contended that understanding
the source of the infection would assist the industry in preparing for the
future, depending on whether the source was determined as local, or from
Associate Professor Knibb advised that WSSV DNA sequences were obtained
from a Logan River aquaculture farm, during the outbreak in late 2016. Further
samples were examined from overseas areas with current WSSV outbreaks, and from
imported highly processed prawn products. Associate Professor Knibb advised
that 'by far the best hypothesis that fits the data is that the Logan River
WSSV is a very recent arrival from overseas'. Some DNA sequences were found to
be 'nearly exact matches' for 'one overseas region'.
Having argued that WSSV entered Australia via an overseas source, the
submission further stated that:
Notwithstanding further testing of overseas samples which
will be ongoing, we believe we now have a match (analogous to matching bullets
from the same gun), and our research will shift focus to discovery of the exact
pathway of entry (we need to find the "gun"); accordingly our
research will now focus on testing Australian retail samples from the
"region of interest".
In response to the genetic testing undertaken by USC, DAWR stated that
it would welcome detailed information from the researchers about their findings
and methods. A DAWR spokesperson said that USC 'have not made the methodology
or data associated with this report available to the department. The department
is unable to provide an informed comment on these assertions'. The spokesperson
also argued that confirming the origin of the virus would not demonstrate the
pathway by which the outbreak occurred.
Associate Professor Knibb argued that the authorities had access to the
same technology used by his team, and greater financial resources, and should
therefore be able to complete the same testing to help determine a possible
source country of the infected product.
However, at a hearing on 11 September 2017, DAWR confirmed to the
committee that investigations to date had not confirmed the cause or pathway of
the outbreak. The department was continuing with genetic analysis to identify
any link between infected prawns in Australia and overseas WSSV strains;
however this work was not yet complete.
DAWR was able to advise that preliminary DNA analysis of two samples
from infected farms, and one from northern Moreton Bay, indicate that the
samples share more than 99.9 per cent nucleotide identity with each
other. These results suggest that the viruses are from a single source, and not
from multiple WSSV incursions.
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