By Development Communication Section
Among the mandates of SEAFDEC/AQD is to disseminate information on aquaculture and to transfer science-based aquaculture technologies to fish farmers and other relevant stakeholders. True to its mandate, SEAFDEC/AQD celebrated its 42nd anniversary with a series of lectures during the Farmers’ Forum and the Dean Domiciano K. Villaluz Memorial Lecture. There was also an aquaculture clinic where fish farmers can interact with AQD’s experts on any concerns that the farmers may have in the culture of various commodities; and capping the anniversary celebrations was the launching of new aquaculture extension manuals and other publications.
Farmers’ Forum and Aquaculture Clinic
More than 100 guests from the private sector, academe, and Philippine government agencies were present during the Farmers’ Forum on 9 July 2015. There were three lectures by SEAFDEC/AQD experts, namely; “Important Findings and Recommendations on Chemical Use in Aquaculture in Southeast Asia” by Dr. Relicardo Coloso; “Individual oysters, the oysterrific choice” by Dr. Ma. Junemie Hazel Lebata-Ramos; and “Standard Operating procedures for Responsible Movement of Live Aquatic Animals for ASEAN” by Dr. Rolando Pakingking Jr. A representative from the Development Bank of the Philippines (DBP) also gave a talk on the “Financing Program for Aquaculture.”
The Farmers’ Forum was followed by an Aquaculture Clinic where fish farmers and other stakeholders can consult for free with SEAFDEC/AQD experts about their aquaculture concerns.
Dean Domiciano K. Villaluz Memorial Lecture
The speaker of the traditional Dean Domiciano K. Villaluz (DKV) Memorial Lecture, held 10 July 2015, was Dr. Ikuo Hirono. Dr. Hirono is a professor of the Laboratory of Genome Science of the Graduate School of Marine Science and Technology at Tokyo University, Japan. His lecture topic was entitled “Recent advances in AHPND caused by Vibrio species.” The following is an excerpt of Dr. Hirono’s talk:
The Early Mortality Syndrome or EMS in shrimp is also technically known as Acute Hepatopancreatic Necrosis Disease (AHPND). AHPND is caused by unique strains of Vibrio parahaemolyticus that have transferrable virulent plasmid carrying toxin genes. A plasmid is a small DNA molecule within a cell that is physically separated from the chromosomal DNA and can replicate independently. The genome of AHPND strains of V. parahaemolyticus from Thailand, Mexico, Vietnam and China have been determined by several different groups. Our group developed the conventional PCR and LAMP methods using a primer set that targets PirA-like toxin genes of V. parahaemolyticus. At present, the accuracy of our developed diagnostic methods for AHPND is 100%. Recently, we characterized the toxin genes of AHPND V. parahaemolyticus. Its plasmid contains two toxin genes that code for toxin A and toxin B. Toxin A and toxin B consists of 110 and 438 amino acid residues, respectively. We constructed recombinant plasmid carrying both genes for toxins A and B. A V. parahaemolyticus non-AHPND strain N7 which is not carrying a plasmid and strain FP11 which is carrying a plasmid but not coding the toxin genes were transformed with the plasmid carrying both toxins A and B genes. The transformed N7 and FP11 strains killed white-leg shrimp, Litopenaeus vannamei same as the AHPND strain. We then fed the white-leg shrimp with commercial feed containing formalin killed AHPND strain of V. parahaemolyticus. In a couple of days of feeding, all of the white-leg shrimp died. These results indicated that the toxins A and B are the virulent factors of AHPND V. parahaemolyticus.
The region encoding the toxin genes is composed of approximately 6 kbp which exhibit terminal inverted repeats of about 1.2 kbp. The repeats encode insertion sequence (IS). The IS encodes transposase and is identical to other reported strains of V. parahaemolyticus. The non-virulent strains carrying the plasmid completely lack the toxin region, but possess an IS. Interestingly, we found that the virulent strains also possess the region lacking toxin genes but have a single IS. These results suggest that the IS might have transposase activity and is involved in the deletion and/or insertion of the toxin genes.
Recently, we found another Vibrio species carrying the same plasmid of the AHPND V. parahaemolyticus. This Vibrio species kills white-leg shrimp similar to AHPND V. parahaemolyticus. This suggests that the transferrable virulent plasmid is spreading at least in Vibrio species in shrimp ponds. Presently, we are trying to develop prevention methods against AHPND.
The DKV Memorial Lecture was then followed by the launching of new SEAFDEC/AQD publications. Three aquaculture extension manuals were launched this year with topics on rotifer culture, milkfish broodstock management, and soft-shell crab production. In addition, monographs on health management of milkfish and chemical use in aquaculture were also introduced to the event’s guests.
These yearly anniversary activities of SEAFDEC/AQD show its commitment in improving and ensuring the sustainability of the aquaculture industry.