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November 5, 2013

The World

EMS—Age and Size of On-Set

 

Originally, it was thought that 45-day-old shrimp at 5 to 8 grams were too big to contract EMS, however, chatter on The Shrimp List, a mailing list for the shrimp farming industry,indicates that that’s not the case.

 

Pamindagan Farm (pamindangan@gmail.com): 45 days and 5 to 8 grams seem a little too late and too big for EMS.

 

Daniel Gruneberg (seagardenfoods@mac.com): 45 days and 5 to 8 grams is not too late for EMS.  We see it in Thailand at that size and age.

 

Christopher Lim Ham Min (chris.lim@bluearchipelago.com): Mortality that happens after 45 days of growout could be a second wave of the disease, after earlier mortality went unnoticed.

 

Daniel Gruneberg (seagardenfoods@mac.com): In Thailand, we have used the names “Early EMS” and “Late EMS” (admittedly bad grammar), but I guess Buddhist dualism allows for “Late-Early Mortality Syndrome” without worrying about the grammar police.

 

During our research for a “cure”, we have had many false alarms of what we thought was working, but the mortalities were only delayed.  It is not uncommon to see mortalities with the same telltale signs of EMS (pale HP, empty mid-gut, sloughed cells in the intestine) at 5 to 8 grams and even at 10 grams and larger.

 

Loc Tran (thuuloc@email.arizona.edu): We have experimentally induced EMS in tiger shrimp (Penaeus monodon) and white shrimp (P. vannamei) at sizes from 0.5 to 10 grams.  We did not test larger sizes, but I think this bacterium could probably knock down larger sizes.

 

Daniel Gruneberg (seagardenfoods@mac.com): Dr. Loc provides additional support for my claim that the “early” in early mortality syndrome is merely an observation that EMS usually hits shrimp farms “early” in the production cycle, but has nothing to do with the size of the animal that is potentially susceptible to the disease. This particular strain of Vibrio parahaemolyticus can kill about any size animal given the right conditions.

 

Padlab (padlab@yahoo.com): It’s possible that the not enough shrimp survived in the affected ponds for EMS to show up in large shrimp.  Has anyone seen EMS in 20-gram or larger shrimp?

 

Loc Tran (thuuloc@email.arizona.edu): An investigation conducted by my colleagues at Vietnam’s Research Institute of Aquaculture No.2 observed EMS hitting shrimp 77 days after stocking.  I assume that those shrimp were around 15 grams, or so.

 

Dr. A. Ravi Kumar (ravialphabio@yahoo.com):  It seems that the initial case definition for EMS may have to be changed.  The time of mortality probably depends on several factors, like the load of V. parahaemolyticus in the pond, the quality and strength of the seedstock, immunity, age of the seed, other bacterial populations in the pond, probiotic applications, and stressors like stocking density, poor water quality, pH, and temperature.

 

Source: The Shrimp List (a mailing list for shrimp farmers).  Subject: EMS Clinical Signs.  October 27 to November 4, 2013.

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