Fletcher et al. (1997) suggest that the size of the outbreak in 1995 are consistent with infection of a naïve Australian pilchard population by an exotic herpes virus to which they had never previously been exposed. The use of imported pilchards to feed caged southern bluefin tuna in South Australian waters provides a potential source of such a virus. This is one explanation that highlights the need for a panel of diagnostic reagents and tests to screen imported pilchards for the presence of the herpes virus.

Herpes viruses are well-known to cause latent infections whose existence remains unknown until a predisposing environmental factor leads to their recrudescence. The factor most commonly recognised in virus reactivation is stress tha tcan itself be induced by a variety of stimuli including infection by another, unrelated microorganism. Fletcher et al. (1997) suggest that the severity of the disease observed in Australian pilchards and its emanation from a single geographic locality are not consistent with reactivation of a latent infection. However, we can not at this time rule out the possibility that the herpes virus is endemic and present in a latent state in Australian pilchards and is activated following infection by and, as yet, unidententified microorganism that spreads from a point source in South Australia. Imported pilchards may or may not be the source of such microorganism. There is a need to rule out involvement of other microorganisms in the death of the pilchards and to use the panel of diagnostic reagients and tools mentioned above to determine if Australian pilchards are latently infected by a herpes virus. Mortalities observed in the juvenile fish populuation in 1998 but not in 1995 raise questions about the role of herpes virus in the recent outbreak. There is a need to determine if herpes virus is present in dead juvenile fish.

Fletcher. W.J., Jones, B., Pearce, A.F. and Hosja (1997). Environmental and biological aspects of the mass mortality of pilchards (Autumn 1995) in Western Australia. Fisheries Research Report No 106, Fisheries Department of Western Australia.

In recent years several mollusc diseases (e.g. Perkinsosis, Bonamiasis, AVG, OOD, ostreid herpes viral disease) have impacted, and continue to impact, Australian fisheries and aquaculture. Similar diseases also affect mollusc aquaculture overseas, e.g. Bonamiasis of oysters in Europe, ostreid herpes virus in Europe and New Zealand. The outcomes of past and present efforts to manage diseases in farmed molluscs have been poor, and few controls have been devised for disease outbreaks in wild populations. Thus these diseases have continued to spread partly due to poor international coordination of response to emerging diseases, lack of sensitive and standardised diagnostic tests, no understanding of whether these diseases arose separately in different countries or whether they have spread internationally, poor understanding of mollusc immunity, poor understanding of pathogen biology in the context of host and environmental change, little information about how the infectious agents are spread within populations, lack of coordinated research on improved measures to avoid disease, inability to predict where and when future threats will arise. These factors suggest a need for an internationally based and coordinated multidisciplinary research approach to ensure the sustainability of mollusc aquaculture and wild mollusc populations. This need was recognised internationally and led to the KBBE Forum workshop on "Disease mitigation and prevention in mollusc aquaculture". One recommendation from the workshop was to hold a future KBBE workshop to address issues concerning mollusc disease diagnostics and would align with several key research areas within the FRDC R&D Plan and be of interest to industry and regulators.