Hepatopancreatic microsporidiosis (HPM) caused by Enterocytozoon hepatopenaei (EHP) is a newly emerging disease of cultivated shrimp in Asia. Current evidence indicates that it can be associated with severe growth retardation that may not be clearly evident until the second month of culture and that it may even cause low continuous mortality in the case of very severe infections.
Here we present a new method for detecting Enterocytozoon hepatopenaei (EHP) that has superior specificity to the first generation SSU-PCR developed in 2009 when the genetic information of EHP was still limited. Due to the urgency in stemming losses to HPM, we have decided to release this method for free, non-commercial use to the global shrimp farming community.
The second generation EHP detection method presented here is based on a gene encoding a spore wall protein (SWP) of EHP (SWP-PCR). Results from our laboratory work revealed, in contrast to SSU-PCR, that the SWP-PCR method did not give cross reactions with DNA from crabs infected with H. eriocheir and E. canceri. From these results, we recommend that the new SWP-PCR method replace the first generation SSU-PCR method.
The sequences of the primers for the SWP-PCR method (nested PCR) are given below and can be used freely for non-commercial applications to detecting EHP. Please contact Centex Shrimp (ornchuma.its 'at' mahidol.ac.th) to obtain a free positive control plasmid (pGEM-EHPSWP).
This report was prepared by the 14th Asia Regional Advisory Group on Aquatic Animal Health (AG) that met at KU Home, Kasetsart University Campus on 23rd to 25th November, 2015. The report provides:
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This disease card describes the diagnosis and range of a microsporidian shrimp pathogen, Enterocytozoon hepatopenaei (EHP), first discovered in Penaeus monodon in Thailand in 2004. It infects only the tubule epithelial cells of the hepatopancreatic tissue of shrimp.
EHP was later found to also infect P. vannamei cultivated in Thailand and is suspected to have been reported from P. japonicus in Australia in 2001. EHP has been reported from Vietnam and is associated with white faeces syndrome. It resembles an unnamed microsporidian reported in the hepatopancreas of P. monodon in Malaysia in 1989 and in P. japonicus in Australia in 2001. PCR positive results have also been obtained from P. vannamei cultivated in Indonesia and India, thus it is probable that EHP is endemic in the Australasian region.
This report was prepared by the 13th Asia Regional Advisory Group on Aquatic Animal Health (AG) that met at Ki Royal Saigon Hotel, Ho Chi Minh City, Vietnam on 22nd to 23rd November, 2014. The Advisory Group was established by the Governing Council of the Network of Aquaculture Centres in Asia-Pacific (NACA) to provide advice to NACA members in the Asia-Pacific region on aquatic animal health management.
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This publication describes the AP4 method for the detection of AHPND-bacteria. The advantage of the AP4 method over the AP3 method is that the it has 100 times higher sensitivity. Because of its higher sensitivity, the bacterial culture enrichment step needed when using the AP3 with low levels of AHPND bacteria may be omitted. However, the AP4 method should not be considered as a replacement for the AP3 method but simply as an alternative choice for the users to choose should they need a more sensitive detection method.
The AP4 method has been tested with the same 104 bacterial isolates that were used for validating the AP3 detection method, and the results were identical, i.e., 100% specificity and sensitivity with the 104 isolates but at 100x lower template levels.
As with the previous announcements in this series, the AP4 method is provided for free use in the detection of AHPND bacteria. A positive control plasmid for the AP4 method will be sent out to those who are already on our mailing list as recipients of plasmids for our previous AP methods to detect AHPND bacteria. For those not already on our list, the plasmid will also be provided upon request to: Dr. Kallaya Sritunyalucksana kallaya 'at' biotec.or.th. To join the mailing list, please visit the AHPND Detection Google Group.
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Acute Hepatopancreatic Necrosis Disease (AHPND) has recently been found to be caused by a pathogenic strain of Vibrio parahaemolyticus. This updated disease card provides a summary and guidance on: