Based on passive surveillance, the common diseases in major commercial finfish farms in Asia include infections with Edwardsiella ictaluri, Flavobacterium columnare, Streptococcus agalactiae, Francisella spp., and iridoviruses (freshwater species), and Vibrio spp., Tenacibaculum maritimum, Streptococcus iniae, iridoviruses and nodavirus (marine species).
Of these diseases, big belly disease (Vibrio spp.), T. maritimum, iridoviruses of marine and freshwater fishes and S. agalactiae of tilapia are the most important in terms of economic impact to large scale commercial fish farms in the region. For S. agalactiae in particular, two biotypes were identified affecting specific countries in the region. Biotype 1 was isolated from diseased tilapia in Thailand, while Biotype 2 from Indonesia and China. Both Biotypes 1 and 2 were found in diseased tilapia from Vietnam.
Disease diagnosis is important, but it is just half the solution. Fish health experts should understand the epidemiology of important diseases, which include analyzing disease spread and transmission, as well as interaction of the disease agents with the production system and other pathogens. The emergence of large scale aquaculture production systems which are often severely constrained by major diseases needs constant surveillance/monitoring for better aquatic animal health management.
- To increase use of fish vaccines in Asia-Pacific, aquafarmers need to have access to more affordable vaccines and simple application procedures (e.g. immersion rather than injection), especially for small-scale farmers and producers of low-value species which are common in the region.
- For streptococcal (S. agalactiae) infection, vaccine is already available for Biotype 2 and is currently being used in Indonesia. No vaccine is yet available for Biotype 1.
- AG recommended that targeted pro-active surveillance and management is needed in the region. In some circumstances, private companies involved in the industry should be encouraged to support active surveillance for them to fully understand the situation.
- In dealing with aquatic animal diseases in general, AG recommended that capacity in epidemiology and fish pathology be strengthened especially for major diseases affecting the aquaculture industry.