Kota Kinabalu: No less than 52 out of 652 tagal areas throughout Sabah’s 236 rivers are affected by the Koi Herpesvirus (KHV) outbreak, according to State Fisheries Director Datin Dr Shuhadah Mustapha.
She said the figure indicates that the spread of the disease has had significant impact on the tagal system, which is a cornerstone of inland fisheries resource conservation in Sabah.
Based on recorded fish mortality data, Ranau and Tambunan are the worst affected. Ranau recorded 12,732 fish deaths, followed by Tambunan with 6,080.
“The estimated total number of pelian fish deaths so far stands at 21,541,” she said.
Apart from pelian, mortality also involved the serawi species (Hampala sp.), which showed similar infection symptoms. However, this was only reported in Kiulu, Tuaran, involving a single fish.
Dr Shuhadah said the outbreak has also affected the inland aquaculture sector, particularly earthen ponds and concrete pond systems that use water sourced from infected rivers. No infections have been reported involving cage culture systems. There are currently no freshwater cage farming operations for pelian in Sabah.
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The Director said the department has implemented intensive monitoring through sampling in affected rivers and aquaculture ponds.
“Samples are sent to the Polymerase Chain Reaction (PCR) Biosecurity Laboratory at the Likas Fisheries Complex as well as private laboratories for confirmation.”
To curb the spread, disposal of infected fish is carried out in accordance with standard operating procedures, either by burning or burial.
“Laboratory analysis has confirmed that koi or carp are the primary hosts of this disease,” she said. Pelian that tested positive for KHV were confirmed using Nested-PCR and sequencing methods, with results showing 100 per cent similarity and 100 per cent query coverage to Cyprinid Herpesvirus 3, consistent with global KHV strains based on phylogenetic analysis.
She said in line with international standards set by the World Organisation for Animal Health (WOAH), an area can only be declared disease-free after undergoing at least two years of monitoring without any detection of KHV. She also noted that previously, the department did not conduct KHV screening tests at aquaculture premises or ornamental fish outlets.
The State Government is now enforcing strict control measures, including a ban on the release of non-native fish into public waters, particularly those from the Cyprinidae family.
In addition, she said a directive has been implemented to regulate the movement of koi fish from tagal areas and public waters, alongside continuous monitoring and enforcement in all affected areas.
Dr Shuhadah said there is no scientific evidence indicating that KHV can infect humans. “The public need not panic as the virus does not pose a risk to humans or food safety.” Nevertheless, she advised the public not to release pet fish, especially koi, into rivers or public waters.
This is to prevent further spread of the disease, including the risk of fish escaping into rivers during periods of heavy rainfall due to strong currents.
