Cape town: Laboratory sequencing has confirmed the presence of pilchard herpesvirus (PHV) genetic material in sardines as investigations continue into the cause of recent sardine mortalities along South Africa's West Coast. In a statement issued on Friday, the Department of Forestry, Fisheries and the Environment (DFFE) reported that PHV was detected in both dead sardines and, at lower levels, in some apparently healthy sardines collected from the West Coast.
According to South African Government News Agency, the findings suggest that the virus alone may not be the sole cause of the mass mortality. The department is investigating whether environmental stressors such as harmful algae, low oxygen, or unusual oceanographic conditions might have triggered or intensified the event, although this remains a hypothesis requiring further evidence.
The department conducted tests for toxins in sardines collected off Saldanha Bay, the Cape Canyon, and Gansbaai, as well as an apparently healthy comparison sample from St Helena Bay. No paralytic toxins associated with a harmful algal bloom were found in Saldanha Bay. However, two other algal toxins, domoic acid and yessotoxin, were detected at low levels, with the highest levels found in the apparently healthy comparison sample. These findings suggest that the toxins tested for were unlikely to have been the primary cause of the sardine deaths, although they do not rule out harmful algae or environmental conditions as contributing factors.
The department has convened an urgent briefing with small pelagic fishing industry stakeholders and will establish a task team comprising of the department, fishing industry, and other relevant stakeholders. This task team will urgently formulate a high-level, coordinated response plan to address the PHV-associated sardine mortality in South African waters. An inter-agency effort is expanding disease surveillance along the West, South, and East coasts, while further disease, pathology, and environmental investigations continue. The department's routine October/November hydroacoustic biomass survey will be the first opportunity to assess the possible effect on the sardine population.
PHV has not previously been reported in South African sardines, although it was associated with large-scale sardine mortality events in Australasia during the 1990s. Subsequently, the virus was detected in apparently healthy Australian sardine populations without causing continuous mortality. PHV is associated with sardines, also known as pilchards, and there is no evidence that it infects people or other animals.
The department stated that the detection of PHV alone does not indicate that healthy sardines caught commercially or canned sardine products are unsafe. The findings do not currently justify a general suspension of fishing or canning. While biotoxin results are reassuring, they do not constitute a general clearance of all commercial catches. Monitoring and normal food-safety controls should continue, and the public is advised not to collect or consume dead or dying fish or feed them to pets.
The DFFE will provide further information as additional results from the ongoing investigations become available.
