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Tracking EHP and WFD The EHP microsporidian is an emerging pathogen affecting shrimp farming in Vietnam and other parts of Asia. ShrimpVet has been working in collaboration with National Cheng Kung University, Taiwan on EHP as well as white faeces disease (WFD). They presented results of the research at the Asian Pacific Aquaculture 2017 shrimp industry session. There are no distinctive gross signs in EHP infected shrimp and the only indication for the farmer is retarded growth. WFD infected shrimp show floating white feacal strands on feeding trays and whitish to golden brown gut. Loc also described WFD histology in gut and hepatopancreas of affected shrimp. Histology of EHP just showed spores in lysed cells and in gut lumen. In a series of challenge tests, the research group confirmed that WFD is a bacterial disease affecting the gastrointestinal track of shrimp. In the case of EHP, Loc said that even if the broodstock is EHP clean, during maturation over 4-5 months, there are risk factors such blood worms, oysters, squid etc being infected and fed to the broodstock. “Within these 4 months, I have seen 60-70% of broodstock contaminated. In one month, 20-30%. This goes on along the chain; nauplii to post larvae and in the grow-out, the microsporidian will multiply. I know that we can avoid such contamination by using frozen feeds. But the question is how available are these feeds. Imported live feeds cost more.” The solution is to inactivate the pathogen in the maturation facility and to routinely check for the pathogen at the nauplii stage. At this stage we can reduce the risks of infection by collecting eggs, followed by washing and disinfection. Next is ensuring post larvae biosecurity and checking with real time PCR

whether post larvae are infected. Next, according to Loc, is the check for infections in the pond sediments. In 2014 when Loc was tracking EHP, he then advised farms on what should be the steps to take, such as preventing contamination along the value chain, from algae to post larvae before stocking in ponds. “Nobody listened as farmers did not want to take any risks. I then added a small prototype hatchery in Ninh Thuan to explain the work required to monitor the microsporidian. Then many large companies picked up the information. They adapted and modified for their facilities. At least I know that ShrimpVet is making a contribution.”

In the end, I do not want aquaculture to be so unpredictable, I want to bring it closer to a science.. - Loc Tran

Wish for industry In 2017, to fulfill two objectives – quick diagnostics and then assisting industry with innovations through the total value chain – Loc set up a 6 ha farm which allows him to try out some ideas on improving farming technology and protocols. He wants to carry out more field trials at different stages or over the whole cycle of shrimp farming and then demonstrate through models. “If we do this right, have higher efficiency, we will be less dependent on antibiotics and have traceability.”

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January/February 2018 AQUA Culture Asia Pacific Magazine

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Volume 14, Number 1 January/February 2018 MCI (P) 011/10/2017 ISBN 1793 -056  
Volume 14, Number 1 January/February 2018 MCI (P) 011/10/2017 ISBN 1793 -056