Disease-translocation across geographic boundaries must be recognized as a risk even in the absence of disease identification: the case with Australian Sardinops

In 1995 and 1998/99 single species massmortalities of sardine/pilchard Sardinopssagax (Clupeidae) spread rapidly throughoutthis species' range in Australia from thecentral coast of South Australia, dramaticallydecreasing the population size and representingthe two most extensive mass mortalitiesrecorded for marine organisms. The behavior ofeach epizootic indicated that an exoticpathogen was responsible, with the fatal agentshown to be a previously unknown herpesvirus. The focal origin of both events from a limitedregion within the extensive Australian range ofS. sagax was not random. Tuna(Thunnus maccoyii) feedlots located in the sameregion as the epizootics' origins areresponsible for delivering to the marineenvironment the largest quantities ofS. sagax imported into Australia, which providesqualitative evidence of a link between the twoevents and imported S. sagax. This linkprovides an example of the need to undertake areview of the current international standardsfor import risk analysis (IRA) that requires adisease to be identified before it can beconsidered a risk. Regardless of the identityof the disease agents responsible, casehistories of mass mortalities need to be givendue consideration in both deciding whether toinstigate an IRA and also form part of the IRA. Identification of a hazard should thus not berestricted to dealing only with identifiablediseases, but should also embrace casehistories of epizootic events linked to (a)previously unidentified pathogens and (b)translocation of particular species betweengeographically separate populations.