The Department of Forestry, Fisheries and the Environment (DFFE) is continuing to monitor new reports of Pilchard Herpesvirus (PHV), which has triggered an unusual sardine mortality event.
The mortality event has now been reported over an area extending from the Western Cape through the southern and eastern coasts, into the northern Wild Coast and along the Namibian coast.
Reports of the event began in July this year.
“PHV has been confirmed in sardines associated with the mortality event, including sardines collected in Gqeberha. PHV remains the leading explanation for the observed mortalities, although the role of the virus and the possible contribution of environmental factors are still being investigated.
“The full extent and impact of the mortality event are not yet known. The DFFE and its scientific partners are continuing to monitor new reports, undertake diagnostic testing and investigate the distribution, scale and progression of the event, as well as its potential implications for the sardine population and the wider marine ecosystem,” the DFFE said this week.
READ | Authorities probe reports of sardine deaths in Gqeberha
The department revealed that laboratory testing has confirmed PHV genetic material in South African sardines associated with the mortality event, including samples collected in Gqeberha.
“This is the first confirmed detection of PHV in South African sardines. Previous surveillance in 2016 did not detect PHV. The historical negative result provides a useful baseline, but it does not establish when PHV may have entered South African waters.
“Detection of viral genetic material confirms that the virus is present but does not by itself demonstrate active disease or causation. Scientists are considering PCR and sequencing results together with viral levels, pathology, the distribution and progression of mortality and other possible contributing factors.
“PHV remains the leading explanation, but its causal role is still being assessed,” the DFFE stated.
The reported coastal span covers approximately 2 600 kilometres between Henties Bay and the northern Wild Coast.
However, the DFFE cautioned that this represents a geographic extent of reported sightings, not an estimate of the number of fish affected.
“PHV has not been confirmed at every mapped location, and the sequence of sightings cannot by itself demonstrate the movement or speed of the virus. Fish movement, ocean currents, uneven surveillance and reporting delays also need to be considered,” the department said.
Investigating causes
The DFFE noted that preliminary investigation does not indicate that the event “mortality represents a large proportion of the overall sardine stock”.
“However, the estimates remain highly uncertain; the event may not yet have fully run its course, and continued monitoring is required.
“It would be inappropriate to describe the stock as unaffected or to imply that uncertainty has been resolved. The current scenarios do not indicate a large proportional stock loss, but the event may not yet have fully run its course. The October/November hydroacoustic survey will provide the first reliable fisheries-independent post-event estimate of sardine biomass and distribution,” the department stated.
The department continues the investigation into multiple potential causes.
“DFFE is implementing a coordinated, science-based response covering disease surveillance, laboratory testing, pathology, environmental investigations, mortality reporting, fisheries-resource assessment, ecosystem monitoring, stranded-fish management, public-health communication and stakeholder coordination.
“The High-Level PHV Task Team coordinates the broader response, while DFFE is working with provincial authorities, municipalities, South African Institute for Aquatic Biodiversity (SAIAB), Rhodes University, the fishing industry, Namibian counterparts and other relevant institutions,” the DFFE stated.
Public health
Regarding public health concerns, the DFFE confirmed that PHV is “not known to infect people”.
“Commercially produced canned sardines processed under approved conditions remain safe to consume. The public should not collect, eat or feed to pets dead or dying sardines found on beaches or at sea, because of the risks associated with decomposition and contamination.
“DFFE and the National Regulator for Compulsory Specifications [NRCS] have confirmed that there is no reason to discontinue consumption of commercially produced canned sardines processed under NRCS oversight.
“Approved canning facilities are inspected by the NRCS, and the validated commercial heat-treatment process used in canning inactivates viruses, including PHV, as well as spoilage-causing and pathogenic microorganisms,” the department assured.
The DFFE strongly advised against collecting, eating, or feeding dead or dying sardines found on beaches or at sea to pets.
“The advice is not because PHV is known to make people ill. It is because the public cannot know how long a stranded fish has been dead or how far decomposition has progressed. Fish that have decomposed may contain harmful bacteria or other microorganisms capable of causing illness.
“Pets should not be allowed to eat dead or dying sardines. The concern is not that PHV is known to infect pets, but that decomposed fish may contain harmful microorganisms or other contaminants. Until more is known about the distribution and persistence of PHV, dead or visibly unhealthy sardines should not be used as bait,” the DFFE warned. – SAnews.gov.za
