The Australian salmon industry is free from the major infectious diseases affecting salmon industries in other countries. Amoebic Gill Disease is the main infectious disease affecting the salmon industry in Tasmania. While this disease occurs in other countries, it does not appear to be as severe as in Australia. The disease-related fish mortalities are greatly reduced by freshwater bathing, however the disease treatment results in greater production costs and reduces the Australian salmon industry’s ability to compete in international markets. While development of a vaccine to protect against the causative agent is a desirable solution for the industry, it must be appreciated that this is a challenging task and requires a long-term view. In the meantime, the industry needs more knowledge of AGD epidemiology and more tools to improve management of fish with AGD on the farms, which would improve AGD treatment and control and decrease the risk of large outbreaks of AGD. As a direct result this should lead to reduced production costs. Improved understanding of the epidemiology of the disease will also provide a valuable basis on which to develop strategies for vaccine application in the future.

The ultimate goal is to have an AGD surveillance system in place, to provide information about the host, agent and environment which is relevant to prevention and management of the disease. The results will improve our understanding of factors contributing to AGD outbreaks and will develop a best industry practice protocol aimed at the reduction of AGD effects on the salmon industry in Tasmania. Information from the surveillance system will facilitate better decisions on the timing of treatments as well as provide long term data for analysis to identify additional management strategies aimed at minimisation of disease risks and economic impacts. Specifically, farm-level surveillance data will eventually provide a basis for measuring spatial and temporal trends in AGD occurrence in both the host and potential reservoirs as well as environmental and production factors associated with changes in AGD occurrence. Analysis of retrospective data will permit the identification of improved management strategies as well as providing farm managers with a more reliable basis on which to make decisions on prevention and control. This project will provide ways of value adding to the data collected by the salmon industry in general. It will protect individual company interests with respect to privacy of commercial information.

There is an urgent need to develop novel treatments which would reduce the impact of AGD on salmon industry. A detailed benefit – cost analysis for the AQUAFIN CRC AGD project was undertaken which gave a Net Present Value of the economic benefit of $21.6M, Benefit/Cost Ratio of 5.3. The current project will deliver the short-term solutions and provide information and advice to the industry on a regular basis.

The current project is part of an integrated research program, with deliverables not only aligned with the development of novel treatments, but also with effective vaccine development, management and other control methods. Developing and maintaining standarised infection is included in this subproject, and it will be crucial for vaccine testing and experimental work within the Host-pathogen interaction project and the Model development – epidemiology of AGD project. The development of a quantitative experimental challenge model is an essential prerequisite to vaccine research and novel treatment testing. Without the quantitative experimental model it is very difficult to compare effectiveness of treatments or vaccines tested in separate experiments. Additionally, the controlled lab infection will provide crude gill isolates to researchers working in other projects.

The growth of the industry and ineffectiveness of freshwater bathing has resulted in the need for the development of new treatments that will either aid in improving current freshwater bathing technology, or offer completely new avenues for the treatment of AGD in Atlantic salmon. Effective treatment of the disease can only be achieved if we understand the physiological and pathological processes at work. To this end it is imperative that we understand:

1. The effect of the parasite on the normal physiology of the salmon so resulting in mortality
2. The effect of the treatment on the parasite
3. The effects of the treatment on fish parasitised to different degrees (I.e., potential toxicity side effects of treatments)

Successful treatments will be rapidly adopted by the industry given the problems with freshwater bathing technology. Advances in the development of either additives to the current freshwater baths or freshwater bath replacement by a less time-consuming chemical treatment will ensure that treatment and control of AGD as a constraint to Atlantic salmon production in Tasmania is eliminated.