Varsha Balu

Aquaculture Genetics (James Cook University)
Understanding disease outbreaks in aquaculture for proactive disease management

Varsha Balu


Disease outbreaks are one of the largest disruptions in production systems and are responsible for large losses in the aquaculture industry. Though it is generally accepted that in a favourable environment for disease development, a disease-causing pathogen can infect a susceptible host to cause a disease outbreak, very few studies use a holistic approach to investigate the association and interactions between the host animal, pathogen, and environment, that could trigger an outbreak. For my project, I will be using advanced ‘omics’ approaches to better understand disease outbreak triggers and develop pathogen diagnostics that will allow farms to detect population changes, intervene early and potentially control these outbreaks. Specifically, my project will determine if early pathogen detection using environmental DNA (eDNA), environmental RNA (eRNA) and environmental proteins (eProteins) can help us understand the disease outbreak triggers of Cryptocaryon irritans (Marine Ich) in barramundi aquaculture.


In the past decade, aquaculture has been the fastest growing primary industry in Queensland, with total industry value increasing by 39.2% between 2018-19 to 2019-20. Barramundi aquaculture is the second largest industry after prawn framing, accounting for about 21% of the state’s production value. In 2019-2020, Barramundi aquaculture production in Queensland decreased by 1.6% compared to 2018-2019, with fewer pond-based farms operating. While numerous reasons could exist for this reduction in production, disease outbreaks could have played a role either due to increased costs in management efforts or loss of produce due to disease related mortalities. Infact, diseases account for almost 50% of production loss in aquaculture systems globally. 

In the past, most disease management strategies were put in place to prevent infection or treat infected animals to maintain productivity and limit further spread of disease. Even the best disease management strategies and practices, however, cannot guarantee complete protection from disease outbreaks, which adversely impacts the disease mitigation process. Current methods of disease diagnostics in aquaculture are often lacking in their ability to detect varying outbreak parameters early, to then be able to control these disease outbreaks or even minimise the impacts. Since pathogens and disease outbreak are responsible for limiting the aquaculture industry’s growth potential, understanding the drivers of outbreaks are vital. Currently, a majority of diseases are only treated when disease presents itself visually, or in terms of loss of production. Very few studies use a holistic approach to investigate the association and interactions between the host animal, pathogen, and environment, that could trigger an outbreak. Therefore, understanding the triggers of disease outbreaks is the first step towards developing an effective disease management practice.

In the barramundi aquaculture industry, the marine ciliate protozoan ectoparasite Cryptocaryon irritans is a serious threat to the fish as well as production output. There is limited knowledge on this pathogen specifically pertaining to barramundi culture in Australia. Investigating the fluctuations in pathogen population dynamics and abundance, links to environmental variables and the host animal responses to this pathogen can be vital in understanding Cryptocaryon irritans outbreaks in barramundi aquaculture. Therefore, the objective of my project is to propose a proactive approach to disease management rather than a reactive one, using novel early pathogen detection tools as well as host health assessment tools, that are rapid, cheap, and farmer friendly. I aim to use the data collected to also develop a predictive model to help pre-empt disease outbreaks, so farms in Queensland, and possibly in Australia and globally, can intervene early, and not lose produce to disease related mortalities.

Role Model

I believe I am a good role model for women and girls aspirating to work in STEM because I pride myself in uplifting the people around me. I always strive to be the best version of myself, both personally and professionally, and I am passionate and dedicated to my projects. As a woman of colour, originally from a third world country, I feel privileged to be able to inspire young girls that look like me and feel as passionately about STEM as I did/do. I feel very strongly about encouraging women to break barriers and to fulfil their dreams, whatever it may be. I believe I have overcome so many challenges to be able to pursue my career choices, having overcome cultural, social, and societal constraints and I can empathize with other women that have had to fight similar battles. I believe Women in STEM is a sisterhood; a community that uplifts one another which is a valuable quality in a role model. Overall, STEM has been male dominated for decades and it is only recently that we see women in positions of leadership. My area of study, aquaculture, is still predominantly male-led, and I would like to see more women leadership in the industry, and I can see myself as one of these women. I aspire to be someone that can mentor and guide young girls to follow the STEM pathway as well as support peers in the field to succeed in their chosen STEM field. 


I have been involved in numerous STEM related activities but mostly in mixed groups, ranging from school and academic groups to citizen science and the general public. My first STEM engagement activity was through Gyan Lab and the Kidovators program, where I designed Science based activities for school aged children, both in summer camp activity format as well as a country wide conference format. I engaged the participants with my main goal being to peak STEM based interest and curiosity in them. I have organised and run numerous Eco-fiesta events at schools in Townsville, holding stalls to create awareness about Marine Debris and their impacts on our planet. I have also been involved in Green STEM programs in some schools in Queensland, promoting good science practices, proper data collection methods and innovation. I have conducted Citizen science-based activities such as island cleans, beach cleans, development of Source Reduction Plans for marine debris, Rubber crumb sand sampling etc. as a Project Coordinator for Tangaroa Blue Foundation as well as conducted science communication tours for the public at the Australian Institute of Marine Science. Through James Cook University, I tutor Science and Maths subjects across university levels, activity engaging my students to get more involve and hands on with STEM activities on campus. I also run “Try your hand at Uni” workshops through the Indigenous Education and Research center at JCU, mainly focussed on Maths and Chemistry sessions. I am also a Library Peer Advisor, where I assist students with their academic needs, with a focus on STEM subjects. I participate in alternate learning platforms, with talks and discussions online as well as social media engagement in the Marine and Aquatic science space. I am involved with Women in STEM university groups and participate in events organised through them. In terms of STEM promotions specifically with women and girls, I have been actively involved in mentoring two Indigenous university students and supporting them through their STEM pathways, assisting and advising them through volunteer positions, internships etc. 


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