Contributed by the Aquatic Pest and Health Policy Section, Animal Health Policy Branch, Animal Division, Department of Agriculture and Water Resource.
Identifying pathogens correctly is critical for Australia’s management of aquatic animal health. During an aquatic animal disease emergency, reliable diagnosis is essential for a rapid and effective response, and to minimise the impact on trade and individual businesses.
Reliable diagnostic testing also supports regular, ongoing aquatic animal health surveillance activities.
Australia has an effective and robust network of diagnostic laboratories, proficient in detecting exotic and endemic aquatic animal pathogens. However, sometimes biological specimens need to be sent to an overseas laboratory to help with diagnosis, as a part of collaborative research, or to contribute to international reference collections.
Working with international laboratories for infectious or parasitic disease testing can provide benefits to Australia’s aquatic animal industries and scientific community.
Sending samples overseas presents some risks but state and territory governments have an agreed approach to managing these risks.
Australia is free from many of the diseases that affect other countries, which gives Australian exporters a trade advantage. Because of this, production costs and costs for export inspection and testing for diseases of concern to Australia’s trading partners are lower.
Demonstrating Australia’s freedom from various aquatic animal diseases supports international trade in aquatic animals and products and also justifies the quarantine policies designed to manage the risk of exotic pathogens entering the country with imported goods.
An incorrect diagnosis, or inaccurate reporting of a diagnosis, may lead to trade partners questioning Australia’s disease status, potentially causing significant damage to international trade of Australian aquaculture and fisheries products.
Australia’s chief veterinary officer Mark Schipp highlights the potential impact of a misdiagnosis.
“In 2012-13, our fisheries and aquaculture industry exports were worth $1.2 billion, representing half of the $2.4 billion gross value of Australia’s aquaculture and commercial fisheries production. Market access for these products can take many years and significant investment to secure, but only a single piece of incorrect information to disrupt,” Mark Schipp says.
“Undoing the damage from incorrect test results in overseas laboratories or the incorrect interpretation of the results can be difficult and expensive. Resolving these issues can take months or years and result in significant impacts on our fisheries and aquaculture industries.”
Most Australian aquatic animal disease diagnostic laboratories operate under a quality-assurance system that gives clients confidence in the reliability of their work.
Laboratories may also be accredited by the National Association of Testing Authorities, whereby they must demonstrate all relevant processes are sound, and participate in proficiency testing for important diseases, both of which provide further confidence in their results.
Additionally, Australia’s laboratories work together to ensure diagnostic results are correct, and where the material produces an unexpected result, it is referred to the national reference laboratory for confirmation.
“When samples are sent to overseas labs, we may lose control of the specimens,” Mark Schipp says.
“Overseas laboratories may not have the same quality-assurance systems in place that we do in Australia so the reliability of their results may be uncertain. If there are any unexpected results, we may not be able to investigate them in the same way we would if the testing was done in Australia.”
He says any spurious diagnostic results could also be made public, with unfair and damaging impacts on industry.
John has recently started work on an Australian fish farm. When animals on the farm begin to show signs of disease, John investigates and takes some samples for laboratory testing.
Having worked overseas, he recognises the signs of disease and considers it best to send the samples back to the laboratory he worked with as they have experience with what he thinks the problem is and would give him a discounted rate.
The overseas laboratory conducts testing on the samples but it does not have a quality-assurance system in place: the samples are contaminated and they mistakenly report a positive result.
The laboratory thinks the results are interesting and reports the result on its public website. As a consequence, the export of fish is suspended to our major trading partners while Australia investigates the finding. John should have contacted his state chief veterinary officer before sending the samples.
The wide availability of molecular diagnostic techniques, such as polymerase chain reaction (PCR) or DNA-based testing techniques, means that rapid and sensitive testing is now possible for many aquatic animal pathogens. Most laboratories have PCR testing capabilities because the techniques are routine and laboratory equipment is becoming increasingly affordable.
However, all diagnostic tests can produce incorrect results, including PCR tests. Good laboratories minimise the likelihood of this and investigate any unexpected results. PCR tests detect genetic material, not viable pathogens, so correct interpretation of test results is essential.
Testing laboratories must be aware of the limitations of diagnostic tests and understand circumstances where results should be disregarded or samples re-tested.
Without follow-up testing (which may not be possible in overseas laboratories due to the type or amount of samples) and the use of additional diagnostic tools to build evidence that a pathogen is truly present, incorrect conclusions can be made.
Mark Schipp says that molecular methods are very useful for detecting pathogens of interest when applied and interpreted correctly.
“Molecular methods test for small fragments of genetic material in a sample and strict laboratory procedures are necessary to prevent misleading outcomes. Incorrect results can occur for many reasons such as sample contamination or problems with test performance,” he says.
“A test for one pathogen can also give a positive result for another pathogen if they are genetically similar. This can be a problem for some viruses because their genome changes over time.”
Australia has several endemic aquatic animal disease pathogens that are related but remain distinct from internationally reportable pathogens. Two examples are Tasmanian aquabirnavirus in Atlantic Salmon, and gill-associated virus (and other yellowhead virus complex variants) in prawns.
Nationally agreed procedures exist to ensure investigations for these pathogens follow a logical, transparent and best-practice approach before a final diagnosis is reached. In these examples, Australian laboratories accurately identified the new pathogen species or strains and could demonstrate their differences from the internationally reportable pathogens.
Without a rigorous and transparent diagnostic approach, presumptive diagnosis of a reportable disease may have led to Australia unnecessarily changing its disease status, triggering costly response actions and damaging our international trade in aquaculture and fisheries species.
Mark Schipp explains that government biosecurity agencies are responsible for responding to emergency animal disease incidents and managing the diagnostic testing to support their investigations.
They also manage the transfer of specimens to overseas laboratories for research or routine work.
If a reportable disease is suspected, or when there is a significant disease event, by law, the chief veterinary officer (CVO) in your state or territory must be notified.
“It is crucial that aquatic animal biological specimens that need to be sent to overseas laboratories are submitted to, and sent by the biosecurity agency. A policy, developed by the former national Sub-Committee on Animal Health Laboratory Standards allows the transfer of aquatic animal biological specimens to overseas laboratories for infectious and parasitic disease testing under research and routine circumstances.
“This policy applies to all testing laboratories, research institutions and anyone who sends biological specimens sourced from Australian animals to overseas laboratories or other agencies for laboratory or consultative procedures.”
The policy requires that the relevant state or territory CVO agrees to the reasons for testing overseas, and he/she must provide written approval for the transfer.
The CVO must also be notified of any test results, and approve the release of any results by those who provided the samples.Mark Schipp emphasises the need to comply with agreed arrangements.
“These arrangements ensure that aquatic animal diagnostic samples are sent through the appropriate channels, information is recorded and reported appropriately and, if necessary, further investigations take place.
“By working with state and territory aquatic animal health officers everyone can help provide industries and governments with confidence in diagnostic outcomes, regardless of where samples are tested.”
Anyone intending to send terrestrial and aquatic animal specimens overseas for disease testing should contact their state or territory animal health officer.
The Outbreak website provides the contact details for state and territory biosecurity agencies, including reporting hotlines for aquatic animal disease.
FRDC Research Codes: 2012-001, 2013-414, 2014-002
Aquatic Pest and Health Policy Animal Division, Department of Agriculture and Water Resources,