Developing diagnostic tests to support aquaculture development

January 15, 2025

The Crawford Fund’s highly sought after Student Awards are one way we support and encourage the next generation of Australians into study, careers and volunteering in international agricultural research.

The awards are funded by our State and Territory Committees and made possible by organisations including ACIAR, international centres, Australian and overseas universities and NGOs who host our awardees.

Applications for 2025 Student Awards are now open! Apply hereWe also have our new undergrad-focused 2025 Henzell Awards too.

We would like to share the experience of 2023 Student Awardee, Jeffrey Ling, a PhD student from James Cook University’s Singapore campus, who travelled to Thailand as part of a collaborative effort and exchange of technical expertise on developing diagnostic tests to support aquaculture development.


“With the Crawford Fund Student Award, I was able to travel to the Center of Excellence for Shrimp Molecular Biology and Biotechnology (CENTEX Shrimp) in Thailand in 2024 to work on a collaborative research project based on Enzyme Linked Immunosorbent Assay (ELISA) to detect IgM levels using sera from a Scale Drop Disease Virus (SDDV) experimental challenge trial,” said Jeffrey.

CENTEX Shrimp is a multidisciplinary laboratory that was formed in October 2001. It is jointly supported by the Faculty of Science, Mahidol University and the National Center for Genetic Engineering and Biotechnology (BIOTEC).  Despite the initial focus in shrimp and its diseases, CENTEX Shrimp is now also involved in finfish disease through the Fish Health Platform.

Barramundi is one of the main aquaculture species cultured in Queensland, and many Southeast countries, including Malaysia, Singapore, and Thailand. In Queensland, barramundi farming is the second most largest aquaculture activity, after marine prawn farming.

Figure 1: Farming sites for barramundi (FAO, 2023)

As the production for barramundi intensifies in many countries, many farms face many significant disease challenges, with high mortalities and substantial financial losses. One of the important emerging viral diseases that affect barramundi is Scale Drop Disease Virus (SDDV), which was first described in 2011, and has reported mortalities ranging from 40-50 per cent.

Today, Scale Drop Disease Virus has been reported in barramundi cultured in many Southeast Asian Countries, including Indonesia, Malaysia, Singapore, Thailand, and Vietnam. Typically, the infected fish are reported to be lethargic, and many of the fish also had darkened skin and loss of scales (one of the hallmark external abnormalities noted in affected fish).

Figure 2: Distribution of Scale Drop Disease Virus.

Barramundi is an important species cultured in Queensland. SDDV is currently exotic to Australia. However, given the proximity of Australia to Southeast Asia, there is a risk that SDDV could be introduced in Australia. Hence, effective screening and surveillance tools are critical in disease management. IgM specific to SDDV (investigated in this study) could potentially be used to as a useful and screening and surveillance tools for farms in Queensland, explained Jeffrey.

Figure 3: Darkened skin and loss of scales (arrows) in barramundi with scale drop syndrome.

“Currently, diagnosis of this disease is largely based on histopathology and molecular techniques such as quantitative or conventional polymerase chain reactions. Histopathology typically reveals extensive inflammation systematically in infected fish, accompanied by necrosis in major organs such as spleen and kidneys. Previous reports also revealed co-infections with other viruses and bacteria,” he said.“The understanding of immune response to a viral infection provides the fundamental knowledge in disease control strategies such as vaccinations. Currently, there are limited studies on the immune response following SDDV infection in barramundi. To further understand the immune response in barramundi, we investigated the antibody (IgM) response in barramundi experimentally challenged with SDDV,” said Jeffrey.

“Results from this collaborative work could benefit Queensland as the detection of SDDV specific IgM could potentially be used as a screening and surveillance tool, further strengthening the biosecurity effort to keep SDDV out of Queensland, Australia,” he said.

“Using the serum mainly from the SDDV experimental challenge trial and several control serum samples from another study, I was able to compare the antibody response between baseline samples and in the serum collected from the experimental groups,” said Jeffrey.

Figure 4: Transferring serum samples to ELISA plates at the laboratory at CENTEX Shrimp: Transferring serum samples to ELISA plates at the laboratory at CENTEX Shrimp.

This work provides a fundamental understanding of antibody response following experimental SDDV infection in barramundi. Future challenge trials may consider screening antibody levels using ELISA prior to challenge trials, as results may be confounded should the fish used for the challenge trials have prior exposure to SDDV he explained.

Broadly, this experience at CENTEX Shrimp, Mahidol University, provides valuable opportunities to strengthen the collaboration between CENTEX and James Cook University, one of the major universities in Queensland with a focus on aquaculture.

“Dr Saengchan Senapin and Dr Ha Thanh Dong are leading researchers who have published extensively in SDDV, including SDDV genome characterisation and SDDV vaccine trials. These are important works in the control of SDDV. Therefore, I have leveraged their experience and expertise in this virus in this collaborative work. I am hoping to set up our platform to perform SDDV serology at James Cook University,” said Jeffrey.

“Following this experience, we will continue to explore future collaborative work to share the strengths and expertise from both institutions. Also, with this experience as a starting point, I hope to facilitate more students from James Cook University and Queensland to work with the research institutions in Thailand,” he said.

“We are currently preparing a manuscript based on this study, and a follow-up study to investigate the seroprevalence of SDDV in Singapore is currently ongoing, following the award of an internal grant,” concluded Jeffrey.