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80% to 90% of Shrimp Ponds Are Dry
Early Mortality Syndrome
Shrimp News (email@example.com): Hi, EMS (early mortality syndrome)—or AHPNS (acute hepatopancreatic necrosis syndrome) as the scientists call it—appears to have reached disastrous levels in Eastern Thailand.
While summarizing this discussion from The Shrimp List, I had to do some interpreting and guessing. If I made a mistake on any of your comments, please let me know and I’ll correct them. Also, the discussion contained some comments that I did not understand and some that were over my head, so I excluded them. You can read all the unedited comments on The Shrimp List.
Daniel Gruenberg (firstname.lastname@example.org): Hi all, today (January 7, 2013) I drove through the main shrimp farming areas in eastern Thailand, from Pattaya, through Rayong and all the way to nearby Trat Province (on the Cambodian border). I was shocked. I estimated that a minimum of 80% of shrimp ponds in this key production area were dry! Even more shocking, no one was talking about why the ponds were dry. Are we ostriches with our heads in the sand, hoping that the early mortality problem will just go away?
In my opinion, the recent EMS symposium in Bangkok reported on a lot of nonsense theories, and I don't see the proper steps or research being taken to get a handle on this problem.
Our farm has implement its own R&D program, but it's still too early to say what the result will be. Our efforts focus on practical methods for coping with or preventing EMS, as opposed to the more academic approach of searching for viruses with electron microscopes. We are not trying to prove Koch's four principles, which aim to find the cause of a disease; we are trying to find management approaches that result in no disease. I wonder if any other large farmer groups are conducting similar R&D programs?
Attilio E. Castano (email@example.com): Daniel I work on the other side of the Pacific, and so far we do not have EMS, but I was under the impression that the Thai shrimp farming industry did not stock in January because of cool weather. That may be the reason why there are so many dry ponds.
Daniel Gruenberg (firstname.lastname@example.org): Attilio, only the less experienced farms do not stock in January. Although feeding is reduced in the winter months, large, modern, well run, Thai farms have been stocking in January for five years now.
I spoke with the three largest hatcheries in eastern Thailand, and they all confirmed that EMS was not only killing postlarvae (PLs), but that it was also killing broodstock!
Since my first email (above), a friend in a police helicopter flew over Chantaburi Province, also in eastern Thailand, and he confirmed that 90% of the shrimp ponds there were dry.
I asked two processors that I have relationships with if they were having problems getting product and they said “yes”. From all the evidence that I have seen, the problem is much larger than the industry is willing to admit.
Attilio E. Castano (email@example.com): Is there a possibility that people are waiting to stock later in the year or do you think this is a permanent situation?
Daniel Gruenberg (firstname.lastname@example.org): During my drive, I saw a lot of emergency harvests and a lot of dead shrimp in the ponds.
The smaller farms and the less experienced farms will wait until February to stock, but they only represent a small part of what I am observing here, especially considering what I hear from my hatchery manager friends that are losing broodstock after only 20 or 30 days in the hatchery. I am afraid that this problem is getting much bigger than most are willing to admit.
Attilio E. Castano (email@example.com): I hope for the good of your industry that this is not as bad as it sounds. With the prices of fish meal and fish oil so high this year, your industry could be in real trouble.
Pamindangan Farm (firstname.lastname@example.org): Hey Daniel, have you found any trend in farming practices that occurred around the same time EMS struck? A theory presented by a Thai professor during a seminar here in Indonesia suggests that the overuse of probiotics and poor management may be the triggers for EMS in Thailand. Some successful farmers have been using the same management techniques for years with no EMS, so why are they having problems now?
It is true that the disease may have originated from imported broodstock?
So far EMS has not been reported in Indonesia, but it could be here and we don’t know about it. The exchange of information among shrimp farmers is rather “guarded” here, and most failures would be covered up as neatly as possible by pond owners and industry suppliers. Most of them are not open minded, but for the sake of the industry, I hope they get better.
During the IMNV outbreak in 2008, a lot of farmers reduced stocking densities and put more emphasis on maintaining good water quality. I’m not sure if that would work with EMS. What are you doing to cope with EMS?
Leland Lai (email@example.com): Daniel, Attilio and Pamindangan Farm, many years ago when EMS started, we had early reports of it originating in the Bohai Sea in northern China (not confirmed), and as the years passed, it worked its way down the China coast to Hainan Island, then to Vietnam, Malaysia and Thailand. I don’t know if it (whatever it is) is following ocean currents or if it is transported with seedstock and broodstock. Most of the Penaeus vannamei broodstock and seedstock in China today originated in the Western Hemisphere, much of it from Hawaii, USA. Interestingly, if it did start in the Bohai Sea, then it was probably not with P. vannamei because China was culturing mostly cool water species like P. chinensis at the time.
Currently, three causes of EMS have been proposed:
1. An unidentified virus
2. A toxin in phytoplankton or zooplankton that’s transmitted on oceanic currents
3. A genetic loss that previously provided disease resistance
Pamindangan Farm (firstname.lastname@example.org): Hey Leland, thanks for your information. As Daniel mentioned earlier in his emails, the problem may be bigger than what is currently being reported. I certainly hope that the current condition with EMS or AHPNS or whatever “they” want to call it gets sorted out pretty soon. There are successful shrimp farmers who have using standard practices for long periods with reasonable success, and suddenly they have been hit by this new syndrome. It’s kind of difficult for these people to analyze what’s going wrong because their practices were successful in the past.
Daniel Gruenberg (email@example.com): I have a strong suspicion that EMS involves immune suppression based on inbreeding depression. I am going to test that theory by obtaining male and female pairs from disparate sources and genetic backgrounds, breeding them, and then growing them to see if they are resistant to EMS.
There may be one or more environmental etiological agents, perhaps a virus, that don’t express themselves until the shrimp are stressed. Under the category of stressing factors, management practices are highly suspect as Pamindangan Farm correctly pointed out.
I would also like to hear from anybody on the list who has seen EMS-like symptoms in P. monodon. Perhaps it is time for a switch back to monodon.
Vijayan KK (firstname.lastname@example.org): Good suggestion. Yes, it makes sense to use multiple species in shrimp farming, something like crop rotation in traditional agriculture. We could rotate American whites, Indian whites and Chinese whites with our majestic black tiger.
Dustin Moss (email@example.com): Group, there is published evidence that inbreeding can negatively affect traits such as disease resistance and other fitness-related traits in shrimp. There is also some evidence that inbreeding depression worsens as environmental quality worsens. Neither of these phenomenon is unique to shrimp and have been reported in other species (although they are not universal). So, inbreeding could be a factor with EMS. However, we still need to understand what is causing the disease—toxins, pathogens or something else. Efforts by farmers to deal with EMS, in the absence of knowing the underlying problem, shouldn’t be discounted either. Examination of breeding stocks, breeding practices, hatchery/farm management and biosecurity should all be on the table, at least until we start to gain a better understanding of the disease and its underlying cause(s).
Pablo Intriago (firstname.lastname@example.org): Hi, I would accept the theory of inbreeding if only vannamei were involved, but monodon is also affected, and I don’t think monodon has been inbred yet.
Dustin Moss (email@example.com): Pablo and others, the EMS issue is complex and if inbreeding is involved (and I have no evidence to support that it is or even a strong opinion that it is) it is almost certainly not the root cause of the disease. However, highly inbred (and presumably immune compromised) stocks may be susceptible to EMS—especially if it’s caused by a pathogen. If this were the case, the pathogen could have then spread to other stocks and species. That scenario is certainly possible. How probable? I have no idea.
Pablo Intriago (firstname.lastname@example.org): Dustin, it is an interesting idea or concept, but it would be like a pathogen jumping to a new host hence developing a new pathology, which by the way is possible. The problem is that no pathogen has been found yet.
Daniel Gruenberg (email@example.com): The EMS problem is certainly complex. The disease cannot be reproduced by exposing healthy shrimp to hepatopancreas from diseased shrimp. If injected with homogenate they will die, but the pathology is different. They all die within 24 hours.
If you inject shrimp with a cell-free extract they don’t die. EMS is always associated with Vibro in the hepatopancreas, but the Vibrio infection seems to be secondary. Dr. Flegel is working on a theory that there is possibly a bacteriophage virus involved. He has also found some gregarines associated with EMS, but he doesn’t think that they are involved in the etiology of the disease.
We know that broodstock are dying within a few weeks of ablation and that the egg quality of females that eventually die is not good.
I studied HIV (human immunodeficiency virus) as a university student. HIV is an interesting virus, but it doesn’t kill; its victims die from opportunistic infections.
I believe that stress factors are pushing our animals over the edge and that immune system cannot deal with the challenge when also faced with stress induced immune suppression. The Vibrio-plus-phage theory is interesting and certainly a possibility. Disease expression could involve Vibrio-phage stress factors.
It is known that:
1. Many of the global breeding stocks for vannamei originated at the Oceanic Institute
2. There is documented evidence of inbred vannamei from certain hatcheries in Brazil.
3. Inbreeding depression results in immune suppression.
Since monodon is also susceptible to EMS, these three factors can’t be the cause of EMS, but they should certainly be considered when looking for the cause.
At my farm we are wiping the slate clean and restructuring our broodstock management and PL production processes. We think we might be pushing our PLs too hard. Densities of 200 per liter result in poor water quality and stress. To improve overall water quality, we plan to redesign our hatchery as a closed system.
There is also a theory that the over use of probiotics is involved with EMS, so we’re not going to use them, or we’re going to produce our own probiotics from pure cultures. We will probably not use Artemia because they are associated with Vibrio and may be a vector for EMS.
I also want to work with both monodon and vannamei to see if I get different results.
As for the inbreeding issue, if possible, I would like to purchase male and female broodstock from different stocks and mate them to see if their offspring resist EMS. I know that this might reduce growth rate, but if there is a homozygous recessive trait that depresses immunity, we may get slower growth but no EMS—if my hypothesis is correct.
Daniel Gruenberg (firstname.lastname@example.org): Dustin, regarding the inbreeding issue, since the Oceanic Institute (OI) is the source of so much of the vannamei genetic material in Asia, I hope/wish that it is doing some analysis of field samples. Here is a reference that you might find useful:
African Journal of Biotechnology. Assessment of the Genetic Diversity in Five Generations of a Commercial Broodstock Line of Litopenaeus vannamei Shrimp. Patrícia Domingues de Freitas and Pedro Manoel Galetti Jr. (Departamento de Genética e Evolução, Universidade Federal de São Carlos, Caixa Postal 676, 13565-905 - São Carlos, SP, Brazil). Volume 4, Number 12, Pages 1362-1367, December 2005.
Dustin Moss (email@example.com): Daniel/Group, OI has spent a great deal of effort acquiring a genetically diverse vannamei population and managing inbreeding within this population. While OI has been a major source of germplasm to the industry whether directly or indirectly, we don’t distribute large portions of our diversity, and we have no involvement in how the germplasm is managed once it leaves our facility. So, how much and how rapidly inbreeding accumulates in hatcheries and breeding programs that receive our germplasm is not known by OI and is really beyond our purview.
In my opinion, breeding programs should be viewed as long term, if not perpetual, endeavors. So, selection goals must be balanced with inbreeding accumulation and maintenance of genetic diversity. This is often difficult or simply ignored in smaller breeding programs (and I suspect some larger ones as well) and is exacerbated in “local” programs that use mass selection and don’t keep breeding records.
In my original post, I didn’t intend to get off on an inbreeding tangent, and I certainly don’t want to divert the conversion away from EMS. I just wanted to point out that inbreeding may play a role in EMS, but it isn’t the root cause. In my opinion, it’s more of an enabler.
Daniel Gruenberg (firstname.lastname@example.org): Dustin, I am in total agreement with you on all points. I did not intend to implicate OI as the responsible party for inbreeding, but merely wanted to point out OI’s unique position as providing the founding stock for many (most?) of the breeding programs for vannamei.
My comments were that inbreeding is likely an issue with many breeding programs and EMS appears to be rearing its ugly head just as we are accumulating enough generations for inbreeding to become a potential major issue.
With OI’s considerable resources, I thought that it would be interesting if it ran some analyses on field samples (if not OI, somebody should be doing this!) and publish the results.
Again, I don’t want to restrict this discussion to EMS, and inbreeding is something that should not be over looked.
I have been involved in breeding program management and understand how easy it is for things to get out of hand, even if records are kept, and in my opinion, runaway inbreeding is very difficult to avoid in most programs.
Jim Wyban (email@example.com): Gentlemen, Pablo is correct. EMS is hitting both vannamei and monodon, which reduces the likelihood that EMS is caused or related to vannamei inbreeding. In Vietnam, most monodon PLs are produced from wild broodstock (non-domesticated, so not inbred) and they suffer losses to EMS.
While no pathogen has yet been identified, I think an infectious agent cause best fits the facts, which are the far ranging biogeography of EMS (China, Thailand, Vietnam), its rapid spread and severe lethality.
The NACA workshop proceedings is a good compilation of known information on EMS:
Presentations by Drs. Lightner and Flegel at the Bangkok GAA meeting also provide some good background information on EMS:
Daniel’s comment that dying broodstock in Thailand are associated with EMS is new to me. I’d like to hear more about it.
Juan Aguirre (firstname.lastname@example.org): Leland, you mentioned that EMS was seen many years ago. When was EMS first reported? We just heard about it last year.
Daniel Gruenberg (email@example.com): Jim, As you know our farm grows both vannamei and monodon, and we saw a differential expression of EMS in the two species. I don’t think inbreeding is the cause of EMS, but it could be part of the problem and should be on the table. I think that we cannot completely discount the possibility of reduction of genetic diversity in both species although the mechanisms for reduction of diversity would be completely different.
I observed a trend towards lower quality monodon PLs prior to EMS showing up in Thailand. We tested PLs from a major monodon breeding program in Thailand and found the results very disappointing. Performance of the twelfth generation PLs was less than that of low-quality wild PLs. I listened to the University of Arizona’s Dr. Lightner’s audio lecture on EMS/AHPNS, and it seems that his group has injected homogenized hepatopancreas from diseased animals into specific pathogen free, healthy shrimp, and they replicate death, but not the pathology.
It may be just an issue of infection route affecting the pathology, but yes it does seem to implicate a biological etiological agent.
I highly doubt the toxin theory as our farm is organic and we don’t use chlorine or crustacides for pond preparation. Also, the disease is associated with broodstock facilities and hatcheries, where toxins are less likely to be found.
At one time we had a source of PLs that did not result in EMS in our ponds while PLs from other sources died. Our farm is a closed system, so the vector could either be bird droppings or something from the hatchery. Since the expression of the disease is consistently within the first few weeks after stocking, the implication is clearly with the hatchery process.
Freddrick Poh (firstname.lastname@example.org): Guys, because of cold weather, China has not started its growout season yet, but hatcheries are already in production. Let’s keep our fingers crossed that EMS will not be a problem in China this year.
As far as I know, vannamei broodstock is not dying in Thailand. EMS is not causing mortalities in broodstock.
Glen Illing (email@example.com): A very interesting discussion. We are still clutching at straws. I doubt very much that this is an inbreeding issue given the diversity of genetic backgrounds of affected stocks.
Daniel Gruenberg (firstname.lastname@example.org): Glen, nobody is claiming that inbreeding is the sole reason for EMS.
It is not known on a hatchery-by-hatchery or breeding-program-by-breeding-program basis what the incidence of EMS is in the field. It would sure be nice to have that data.
The limited published information on shrimp breeding programs shows a very high percentage of inbreeding. All I am saying is that this issue should be looked at. There is a lot of circumstantial evidence that points to high inbreeding in PLs sold in Asia. Professional breeders agree with this assessment. For those that are familiar with Asian culture and management practices, the warning bells are ringing.
Glen Illing (email@example.com): Daniel, I agree wholeheartedly with you that inbreeding can be a major issue and challenge for a vast number of breeding programs in Asia and elsewhere. But as a root cause of EMS. I am not on that page.
The shear fact that EMS issue is so widespread, covering so many countries and affecting such a large number of unrelated shrimp populations simply speaks volumes. Inbreeding does not create many blips on my radar screen. I agree that it would be extremely interesting to have the data on affected animals and their origins hatchery by hatchery. Perhaps then populations that are susceptible and resistant to the syndrome could be identified, and we could find a way out of the our conundrum.
However for now suffice it to say that it is clear this is not a single gene population issue and therefore not inbreeding as the prime (or even secondary cause).
Daniel Gruenberg (firstname.lastname@example.org): Glen, if one believes that inbreeding is an issue, the logical extension is that immune suppression goes hand in hand with inbreeding. From my hatchery experience, I learned that immune suppression is also related to EMS, so the logical links are all in place. I must also correct your understanding of population genetics. Inbreeding does not only affect single gene issues. Inbreeding increases homozygosity throughout the genome, thereby increasing the statistical chances of deleterious homozygous recessive genes expressing themselves. So perhaps we need to agree to disagree on the possible link between inbreeding and EMS.
We do know that if we subject broodstock to stress, EMS will not only develop in the offspring of that broodstock, but that the broodstock will also die. Stress is also related to immune suppression. For these reasons I want to know what would happen if I crossed males and females from disparate genetic backgrounds to see if there is a relationship to EMS expression. I will do the experiment and the data will speak for itself.
Dallas Weaver (email@example.com): The inbreeding question and problem is very interesting, especially when dealing with highly fecund animals with highly variable survivals with each spawn. In some fish culture systems, where you get a million plus eggs from a single spawn combined with highly variable survival ranging from near zero to 75%, you can kill your genetic diversity in one generation with your effective breeding population going from 50 pairs to 2 in a few generations. You can meet your annual production goals with a few of the high survival spawns. Unless you can track individual families, if you select the next generation from the survivors, you can easily end up with genetic problems in a few generations. Survival in a hatchery, fast growth rates and high fecundity may inadvertently select for all sorts of things you don’t want.
Leland Lai (firstname.lastname@example.org): Dustin and Daniel, near the beginning of this discussion, Pablo Intriago said, “No pathogen has been found” that causes EMS. Perhaps the pathogen has mutated, affects multiple species and has been overlooked in PCR (polymerase chain reaction) tests as an “unknown” pathogen. We may be looking for something new but not detecting it because we’re overlooking variations of a known pathogen. The effect may manifest itself differently and get magnified by inbred, immune-compromised stocks.
Here are some notes from The American Phytopathological Society’s (a nonprofit professional, scientific organization dedicated to the study and control of plant diseases) webpage on mutations. The notes in brackets are Leland’s.
“Mutation is a weak force for changing allele frequencies, but is a strong force for introducing new alleles. Mutation is the ultimate source of new alleles in plant pathogen populations. It also is the source of new alleles that create new genotypes (such as new pathotypes) within clonal lineages [of pathogens]. Small populations have fewer alleles due to genetic drift [as in inbreeding] and also because fewer mutations are generated in a small population. ....Plants and pathogens have coevolved for the longest time at the center of coevolution, leading to selection for a diversity of resistance alleles in the plant population. This is why plant breeders seek resistant germplasm at centers of diversity. If the pathogen coevolved with its plant host at the center of origin, we predict that the pathogen population also will exhibit maximum diversity at the center of origin [with possible increased odds of mutation and deleterious effects].”
Pathogens evolve and mutate. Mutations of known pathogens could be more virulent to resistant lines in the shrimp selection program.
Daniel Gruenberg (email@example.com): Again, in hatcheries in eastern Thailand, recent reports are that broodstock die within 30 days of ablation. Moreover, the first crop of PLs perform relatively well, but as time from ablation increases, the PL quality will decrease. Incidence of EMS also increases with the time from ablation.
I differ with people who think monodon’s susceptibility to EMS is prima faci proof that EMS doesn’t involve inbreeding. Firstly, the quality of monodon larvae from local broodstock has been noted by myself and others on this list for the last five years. Secondly, all the factors are in place for reduced genetic diversity in the wild population of monodon, especially in Thailand where natural stocks have been decimated by overfishing and other environmental factors. Thirdly, nobody says that inbreeding is the sole cause of EMS; they say that the weakened immune status resulting from inbreeding makes the animals more susceptible.
I do believe that Dr. Flegel’s bacteria-phage theory does fit much of the known etiology for EMS, but I still have significant reservations about it. It has not been possible to replicate the disease pathology simply by injecting diseased hepatopancreas into healthy animals because the pathology of EMS is complex and the final lethal stages invariably involve secondary Vibrio infections, so if you infect healthy animals with late stage hepatopancreas from sick animals, they will immediately die from vibriosis. I am a bit confused as to why antibiotics wouldn’t be effective in a phage-bacteria etiology, which leaves the door open to gregarine type parasites that are inherently difficult to detect. Previously, I believe some gregarines have been implicated in white feces syndrome. The gregarine hypothesis actually fits the existing data better than anything.
I think we have to try using earlier stage infectious material as the starting point (prior to massive Vibrio infection) and also look at different experimental routes of infection. But I strongly believe that we will find an infectious biological agent associated with EMS in the near future.
Hypothetically, inbreeding would exacerbate susceptibility to the purported infectious agent.
Here’s the abstract of a study on the effects of inbreeding on vannamei performance:
“The objective of this study was to investigate the effects of inbreeding on the performance of Pacific white shrimp, Penaeus (Litopenaeus) vannamei, under various culture conditions through a retrospective analysis of family performance data. Fourteen years of pedigree and eight years of performance data from Oceanic Institute’s selective breeding program were used in the analysis. During this period, shrimp performance was evaluated in growout trials (in pond and raceway systems), laboratory challenges to three isolates of Taura syndrome virus (TSV), and a laboratory challenge to whitespot syndrome virus (WSSV). The effects of inbreeding on growth and survival were estimated by regressing family phenotypic means (adjusted for contemporary group effects) on inbreeding coefficients. During growout, inbreeding had a small but significant effect on growth (2.6 to 3.9% reduction per 10% inbreeding) but had no effect on survival. The effects of inbreeding on survival after exposure to viral pathogens ranged from moderate (8.3% reduction per 10% inbreeding) to severe (38.7% reduction), although not all effects were significant. Furthermore, the effects of inbreeding on survival appeared to be sensitive to environmental quality, as inbreeding depression was more severe in more stressful environments (smallest effect during growout trials and largest effect during exposure to WSSV). These results suggest that moderate to high levels of inbreeding (N10%) should be avoided in shrimp breeding programs, especially when shrimp are reared under stressful conditions. In addition, the effects of inbreeding on survival appear to be significant enough to justify the use of inbreeding as a germplasm protection strategy (under certain scenarios) for genetic improvement programs.” Source: Aquaculture. Effects of inbreeding and growth of Pacific white shrimp Penaeus (Litopenaeus) vannamei.Dustin R. Moss, Steve M. Arce, Clete A. Otoshi, Roger W. Doyle and Shaun M. Moss (Oceanic Institute, 41-202 Kalanianaole Highway, Waimanalo, HI 96795, USA). Volume 272, Supplement 1, Pages S-30 to S-37, 2007.
Pablo Intriago (firstname.lastname@example.org): Daniel, as far as I am concerned, I do not have any doubt that inbreeding will increase susceptibility to pathogens. A documented example was the outbreak of Taura syndrome virus (TSV) in Venezuela in 2005, which by the way I witnessed. In brief, TSV hit Venezuelan vannamei after 20 years of inbreeding and stopped after we imported fresh stocks from a hatchery in Florida, USA. You might be able to solve your problem by refreshing your lines.
Dustin Moss (email@example.com): Daniel, I think your comments have been clear, and I never thought you were suggesting that inbreeding was the root cause of EMS.
Below are the references for a couple of OI studies that list members might find interesting. They do not involve EMS, and they do not support arguments for or against the role of inbreeding in EMS. They do, in my opinion, show that inbreeding can accumulate rapidly and that inbreeding can have negative effects on performance (at least for some traits).
1. Journal of World Aquaculture Society. Inbreeding Effects on Hatchery and Growout Performance of Pacific White Shrimp, Penaeus (Litopenaeus) vannamei.Dustin R. Moss (Oceanic Institute, 41-202 Kalanianaole Highway, Waimanalo, Hawaii 96795, USA), Steve M. Arce, Clete A. Otoshi and Shaun M. Moss. Volume 39, Number 4, Pages 467-476. 2008.
2. Global Aquaculture Advocate. Shrimp Copyright: Inbreeding Strategies Effective Against Illegal Copying of Genetically Improved Shrimp. R.W. Doyle, D.R. Moss (Oceanic Institute, 41-202 Kalanianaole Highway, Waimanalo, Hawaii 96795, USA) and S.M. Moss. Pages 76-79. April/May 2006.
Daniel Gruenberg (firstname.lastname@example.org): Dustin, thanks for the additional information.
I do believe that it is high time to look into inbreeding as a general health concern in vannamei stocks and that it could be a factor exacerbating EMS susceptibility.
As I have said previously, I am confident that we will find a biological agent responsible for EMS in the near future.
Just as whitespot outbreaks resulted in better management practices in Asia and the Taura virus resulted in similar improvements in management practices in Latin America, I do believe that EMS will have to be addresses with overall improvement in management practices. Management of inbreeding is part and parcel of this improvement in rearing practice.
I believe we will discover two possible infectious routes for EMS. We have observed early EMS and late EMS in Eastern Thailand. Presumably, early EMS, which usually hits within two to three weeks of pond stocking, represents infection from the hatchery stage. Recently, we have heard reports of late EMS, which affects ponds 30 to 45 days after stocking. I hypothesize that we are dealing with an infectious agent that releases spores or cysts into the soil and what we see with so-called late EMS is the same disease with similar pathology, but with the infectious route from pond soil-borne cysts.
Again, I agree that vibriosis is a secondary infection and that anything we can do to improve the general health status both in the hatchery and in the pond—like reduction of density, improvement in water quality and the microbiological environment, reduction of inbreeding and improvement in nutrition—should all serve to improve resistance to EMS.
I am planning to run some experiments with healthy PLs in ponds recently affected by EMS and ponds never affected with EMS to see if there’s a difference. My prediction is that there will be a significant difference!
More Information: Everything You Wanted to Know about EMS/AHPNS—Except What Causes it
Sources: 1. The Shrimp List (a mailing list for shrimp farmers). Subject: EMS. January 7-10, 2013. 2. Summarized by Bob Rosenberry, Shrimp News International, January 15, 2013.
Comments and Updates
Man Heng Soo (email@example.com): “I believe EMS is caused by PLs ingesting too much lime.”
• Shrimp farms are invariably close to coastal habitats and most are located in acid
• All shrimp farmers uses lime.
• Higher stocking densities result in an increased use of lime, and so do biofloc ponds.
• Prior to the onset of EMS juveniles excrete “white” feces.
• The entire alimentary canal is eroded with lesions and the hepatopancreas
I haven’t come across any research papers that discuss this topic. Whenever a new disease hits the shrimp farming industry, it is the pathologists who lead the discussion, however, when EMS first hit the industry and continuing through to the present, no pathogens have been implicated with EMS. This is a travesty because environmental factors tend to be ignored, and we get no closer to the truth. Has the research community questioned the environmental side effects of over liming? The Shrimp List has!Source: Email to Shrimp News International from Man Heng (firstname.lastname@example.org). Subject: Early Mortality Syndrome—A Biologist Point of View. January 15, 2013.
Leland Lai (email@example.com): Has anyone compared EMS survivals between green algae and brown algae (biofloc) ponds? I know that whitespot virus has shown some attenuation in areas where biofloc conditions exist, and I have also heard that EMS will strike brown ponds when biosecurity is not tight. Hence, the issue of pathogen or toxicity may be partly contingent on the channels of transmission (toxicity and water control) or exclusion (pathogen by biosecure approaches). Source: The Shrimp List (a mailing list for shrimp farmers). Subject: EMS. January 16, 2013.
Kelly Hegerle (firstname.lastname@example.org): Vietnam has been dealing with EMS for a couple of years now. Daniel asked if anyone out there was looking for practical solutions. There are thousand of shrimp farmers in China and Vietnam looking for them everyday. Most of them are not doing scientifically controlled experiments, but their work is still valid. It’s a shame that the scientists are not looking for management solutions to the EMS problem.
I have a hatchery in Vietnam and my information comes to me from my sales staff and thus is second hand. They said that good pond preparation and good postlarvae (PLs) help, but that helps with any disease. One thing that definitely works is polyculture with fish. Shrimp stocked with fish or in water from a fish farm do not get EMS. Other things that work at least part of the time are clear water in the hatchery and heavy biofloc in the ponds! Lowering stocking densities doesn’t seem to help. Some regions seem to get hit hard by EMS, while others have intermittent attacks.
Penaeus monodon is just as susceptible or more susceptible than P. vannamei. Early stockings of monodon last season were particularly hard hit. Most monodon are produced from locally caught broodstock. Our hatchery is located in the middle of one of the hardest hit regions in Vietnam, and we have not seen an increase in mortality in our broodstock or any reduction in PL production, but we are very careful to treat all of the water coming into our hatchery. We keep our broodstock for four months and occasionally a little longer. All of our broodstock are imported from Shrimp Improvement Systems. It is not known if PLs are a source of EMS. Not all farmers who buy PLs from us get EMS, but some have. We like to think our PLs are less likely to get EMS. Certainly if PLs are a source of EMS, they are not the only source. If PLs are the source, it is because the PLs or broodstock were infected at the hatchery. There is no indication that imported broodstock from reputable sources is a source of EMS.
Lined ponds are just as likely to be hit by EMS as unlined ponds, maybe more so.
EMS is a serious problem in Vietnam, but we are still producing a lot of shrimp. Source: The Shrimp List (a mailing list for shrimp farmers). Subject: EMS. January 16, 2013.
Daniel Gruenberg (email@example.com): In the near future, I am going to try a completely abiotic clear water hatchery system with continuous filtration in my larval rearing tanks. I’ll let you know how it works out. Source: The Shrimp List (a mailing list for shrimp farmers). Subject: EMS. January 16, 2013.
Erman Tjia (firstname.lastname@example.org): Dear Group, I can attest to the fact that biofloc has helped tremendously in combating whitespot and IMNV in Indonesia. There have been no outbreaks of EMS reported here so far, but it is consoling to hear from Kelly that heavy biofloc helps reduce EMS in Vietnam, although he also said that lined ponds, which are often biofloc ponds, may be more likely to be hit with EMS.
Flockers here have evolved from the initial stage of racing to produce the fastest and thickest flocs to the current thinking of floc for better water quality management in terms of Vibrio suppression (which previously used to show its ugly head around the 40th day of culture) and curbing NO2 (which previously was thought to be part and parcel of a biofloc regime). In doing so, they frequently used heavy doses of probiotics, which seems to go against the current suspicion that rampant use of probiotics might play a role in EMS outbreaks.
My advise—purchase the best PLs available, even if the hatchery is far away. We pay 80% more to have PLs flown in, versus delivery from local hatcheries. I think it is wise for farmers to reward the hatchery that is willing to take the extra steps in ensuring better quality seedstock. Abandon your least-cost mentality; it might wind up costing you a lot of money. Source: The Shrimp List (a mailing list for shrimp farmers). Subject: EMS. January 16, 2013.
More Items from The Shrimp List on EMS
Daniel Gruenberg (email@example.com: Pamindangan Farm [a person], you call the EMS agent a “virus”. My background is in virology, and I feel confident that EMS is not a virus. We have purposely left dead shrimp from a previous EMS attack in the pond and then restocked it to see if we could reproduce the disease. The shrimp grew to harvest size without EMS! If EMS were caused by a virus, one would expect transmission of the disease. Therefore, I suspect a biological agent with the transmission taking place in the hatchery. Perhaps a parasite with a complex life cycle is involved in the transmission, but it is highly unlikely that EMS is caused by a virus.
Om Pamindangan (firstname.lastname@example.org): Kelly Hegerle mentioned that EMS seems to be a hit or miss situation on Vietnamese shrimp farms, therefore, I think it’s important to consider the ecosystem and growout practices of each farmer to determine if EMS/AHPNS is triggered by management practices during pond preparation and early growout. Reduction of stocking densities helps in getting water quality parameters under control. If a farmer is doing things that are against the nature of shrimp farming (for example, the excessive use of chemicals), stocking densities would, of course, not be an issue, and he would probably experiences crashes anyway. I would like to see data from a farm on feeding, stocking density, probiotic use, disinfectant use and aeration practices before it was hit with EMS.
Here in Indonesia, I have not seen or heard of any intensive shrimp farmer (high stocking densities) who has tried polyculture with fish. My opinion is that regardless of PL quality (something that is out of my hands as a farmer), I can only improve my situation by trying to create a positive ecosystem for the shrimp during growout. Simply put, a baby born in a third world country that grows up in Manhattan, New York, USA, would have different antibody and health issues compared to a baby born in Manhattan that grows up in a third world country.
Daniel, wishing you the best of luck with your experiments on various inbreeding processes and water systems. All of us hope that your results will shed some light on the gloom and doom hanging over the EMS-stricken shrimp farming industry in Asia.
Erman Tjia (email@example.com): Daniel, kudos to you, you seem like someone who likes to do things that are outside of the box. We need more of your kind in this business. Keep it up. Best of luck. Fresh perspectives and ideas are sorely needed. I know that it’s a lonely path, but I can ensure you that you have many supporters out there.
From reading your and Kelly’s posts, it doesn’t look like things are all that bleak. At least it does not appear to be “all bad”. What appears to work or help—like polyculture with fish, using clean water and PLs and bioflocs—are the same measures that worked against other diseases, like IMNV and whitespot. I worry, however, that we will set up all the firewalls known to us and still fail. I will leave the identification of etiological agents to the scientist for I am not a scientist (I did not even finish my engineering degree in the USA), but I don’t see how it will help farmers if EMS is being caused by a virus. When the day comes that we have to be rocket scientists to be successful shrimp farmers, we are doomed. I have always encouraged fellow farmers to embrace the Apple iPad philosophy—make it simple and instinctive.
Bforice (firstname.lastname@example.org): Hello, I was wondering if there is evidence of EMS in semi-extensive ponds with stocking densities of 10-15 PLs/m2, like those used in Central and South America. Is it likely that EMS will make its way across the ocean to Latin America, like whitespot did?
Hank Bauman (email@example.com): Keeping live shrimp from Asia out of the Western Hemisphere will likely keep whatever is causing EMS out as well.
Ecneil2 (firstname.lastname@example.org: Hank, no live, EMS shrimp have infected other shrimp.
Hank Bauman (email@example.com): I understand that no one is sure what is causing EMS—toxicity, genetics or an unknown disease—all the more reason for continued biosecurity in the Western Hemisphere.
David Griffith (firstname.lastname@example.org): Hank, what about the live, wild monodon in the Western Hemisphere?
Hank Bauman (email@example.com): Well played David...well played...they’re here [in Belize] in all the farm ponds!
Andrew Winks (firstname.lastname@example.org): There are a lot of very clever people (and I mean that sincerely) posturing about the cause of EMS, but the fact is that no one has an answer! Meanwhile, our lame duck Aussie Government allows fresh and frozen shrimp imports without hardly batting an eyelid, a position that could cripple the local shrimp farming industry.
Patricio (email@example.com) Hi, considering David’s comment, is there evidence that the wild catch of monodon has fallen?
Hank Bauman (firstname.lastname@example.org): The likelihood of transferring EMS to Central America should be very small as long as we don’t import any live shrimp from Asia. That’s how whitespot got here. Belize has kept its doors closed to live shrimp imports since 2002, with the exception of broodstock from Shrimp Improvement Systems in Florida, USA, and we are still free of whitespot, despite the fact that we’re surrounded by it.
I’ve heard there is a wild monodon fishery in Brazil and that fishermen are catching them in the Gulf of Mexico. They’re showing up here in ponds, too. It appears they’re here to stay. We saw more monodon this year than last.
Eduardo Ballester (email@example.com): Just to keep the record, there is no monodon fishery in Brazil.
Daniel Gruenberg (firstname.lastname@example.org): Hank, we don’t know what causes EMS, but I can assure you that biosecurity is not the issue with respect to EMS. We have purposely left dead shrimp with EMS in our ponds, refilled the ponds and restocked with new PLs and the new PLs did not get the disease. So you are best to focus your efforts on good rearing practice rather than trying to prevent the entry of live or frozen animals into your country. Whatever the vector is, sick animals are not it.
Pamindangan Farm (email@example.com): Daniel, oops, my bad, sorry for the inappropriate choice of the word “virus” to describe EMS/AHPNS. Dr. Donald Lightner, the shrimp disease expert at the University of Arizona in the USA, has tried reproducing the disease by injecting healthy animals with extracts from frozen EMS-positive animals, and the healthy animals did not get sick. I like your idea that EMS resembles HIV where it basically “opens the gate” to other parasitic diseases into the immune system of the person. By the way Daniel, on your EMS-positive shrimp, do you find that the shape of the hepatopancreas or excretory system of the shrimp is any different from normal shrimp? Are there any bent or crooked body parts that are supposed to be straight?
Anyway, what I am curious in finding out is actually what triggers the disease because it seems to be hit or miss according to Kelly’s statement. With bird flu, every single chicken that comes in contact with an infectious carrier gets sick and dies. In the case of EMS/AHPNS, that doesn’t happen. Are the affected farms using excessive chemical products during pond preparation stage and early culture? Do they use excessive probiotics as mentioned by Dr. Chalor Limsuwan [a slow opening PDF], a shrimp disease specialists in Thailand? Are these farms mainly densely stocked ones with poor management? Are the ponds using aeration?
I would like to run a small backyard experiment in a 1 x 1 or 2 x 2 meter pond (or aquarium to minimize the cost) stocked at 150-300 PLs/m2 and under aerated/over feed to find out what happens during the early stages of culture. Location of such experiment would have to be as far away from my farm as possible due to biosecurity. Any additional input on what I should do?
Erman Tjia (firstname.lastname@example.org): Dear Pamindangan Farm, last month I briefly visited to the state of Perak on the northwest coast of peninsular Malaysia. Although I did not visit any shrimp farms, I did talk to a few shrimp farmers. EMS is hitting them very hard. One farmer summarized it very nicely. He said they are not afraid of whitespot and that they can still make money with IMNV, but when he mentioned EMS, he looked like a deer caught in the headlights of a big truck. Farmers are puzzled and clueless as to what to do. As you know, my area in Medan, Indonesia, is just across the Malacca Strait from Perak, so are we all quivering about the possibility of EMS hitting us? Not at all, because we are too busy battling a whitespot outbreak, which has hit a significant number of farms. So, if we cannot handle whitespot and IMNV, will we be caught with our pants down when and if EMS hits us?
Daniel Gruenberg (email@example.com): Erman, we have a working hypothesis on the cause of EMS that fits with most of the known data. We are cooperating with several companies on possible treatment/prevention methodologies and should have some results within the next month or so. Let’s keep our fingers crossed. When I have progress to report, I will post it to The List.
Erman Tjia (firstname.lastname@example.org): Daniel, thanks, we all look forward to seeing your results. I am anticipating something that might be anti-establishment and unorthodox. It’s frustrating when our best is just simply not good enough. As shrimp farmers, we have too many of these moments. I also think that shrimp farmers are very resilient lot. These moments can only drive us to go outside our comfort zone and take that extra flight of stairs to look farther and wider and thus have our moment of epiphany. Four to five years ago, I was really enjoying all the “goodies” of bioflocs. I felt that I could do no wrong (irrespective of PL quality)—until IMNV struck. It hit us much later than the rest of Indonesia, and my farm became a regular customer of that disease. To deal with IMNV, we started the Starbucks Shrimp Club, a loose, informal association, a place where shrimp farmers could talk and learn from each other. In short, we encourage each other to look at things with a fresh perspective, to question old standards and to set up new ones.
Medan has a number of cases of whitespot. One big group is doing relatively well. It has its own broodstock facility and hatchery, runs its farms with strict protocols and tight biosecurity, uses relatively low stocking densities (50-60 PLs/m2) and earthen ponds with some lined dikes. It also uses molasses, but as far as I know, no probiotics.
Farms with earthen ponds that stock less to avoid IMNV, which is thought to be correlated with stocking density, are more susceptible to whitespot. Lined ponds perform better, especially those that also use bioflocs. Lined ponds stocked with local area PLs seem to perform less well, except on farms that have relatively low stocking densities and use water from tilapia ponds.
Daniel Gruenberg (email@example.com): For all of those on the list that doubted my claim as to the impacts that EMS is having on Thailand, I have now spoken with a friend who sells shrimp feed, and he confirms that the volume of feed sales, compared to the same month last year, is down 80%, so it is unequivocal that there is currently a huge impact, at least in Eastern Thailand. In addition, I have spoken with the owner of a medium to large-size processing plant, and he says so far the last few months have been the worst he has experienced since he built the plant.
Again, at my farm, we have what we feel is a reasonable working hypothesis on the cause of EMS and are currently testing three different methods for dealing with it. We have the cooperation of two other farm sites, one in Thailand and one in China, so our results should be fairly robust.
I will report back to The List once we get some results.
Daniel Gruenberg (firstname.lastname@example.org): Hi Erman, my farm has a good track record. We have harvested more than 90% of the PLs stocked over the last five years. On a pond-by-pond basis, we harvested well over 98% of the ponds stocked over the last five years. We are the only certified organic farm in Thailand. We have innovated the use of autofeeders in shrimp farming both on the hardware and software side; we have developed a system that replaces the use of lime and still maintains steady pH; we have closed our system so there’s no discharge; we only add new water to compensate for evaporation; and we have developed our own organic feed formula using the latest extrusion technology, which has resulted in 30% improved FCR over CP feed (large scale testing currently underway).
We have a track record of success and innovation and our philosophy is to work with nature as much as possible. We believe this is very important. It also serves as our guide regarding EMS. It is still too early to say, but I think my current hypothesis explains most of the peculiarities of the observed data, and I have high expectations that we can be on the leading edge of the solution as well.
Kanisorn Tanthien (email@example.com): Hi Erman, my name is Tan, and I farm shrimp in Surat Thani, Thailand, one kilometer from the Donsak-Samui ferry pier. I joined a group last year and closely monitor the shrimp farming industry. Previously, I used lots of chemicals in my ponds, but they didn’t help. My shrimp still got infected with whitespot. Since I switched to organic farming in 2006, I have not had any problems with disease, including EMS. I don’t line my ponds, don’t use bird nets, or any biosecurity. My stocking density is 60 PLs/m2, and I produce year round. I do, however, have some production problems related to changes in the weather. I buy PLs from several hatcheries. I never remove the sludge after harvest. I use Dr. Claude Boyd’s, a University of Alabama water quality specialist, plowing technique and add some enzymes and worm tea [below] to my bottom soil. Worm tea balances pH and is loaded with minerals. Trust me. After stocking, my PLs feed on natural feed made from pond sludge. From my point of view, shrimp diseases are caused by a bad environment, waste and over production.
Erman Tjia (firstname.lastname@example.org): Hi Tan, I loved your story, and thank you for sharing it, another example of “Yes we can!”
I think organic farmers are teaching us a major lesson: Killing all the pond life to get rid of the virus vectors may be the wrong approach.
Tan, you don’t clean your sludge? How many crops can you produced without having to remove the sludge? Is it a standard practice for organic farmers to leave the sludge alone after harvest?
You’re stocking 60 PLs/m2, which is also becoming the “in” number in Vietnam. A few turnaround stories in my country are stocking at that level, down from previous consensus of 80-100 PLs/m2.
What is a worm tea?
Kanisorn Tanthien (email@example.com): Hi Erman, I use very little lime and no quick lime or hydrated lime. Decomposing sludge releases acid, which I rectify quickly by degrading it with bacteria. So there’s not much sludge. After five or six crops, if the sludge builds up, I might remove it to the pond banks. After harvesting, I let the pond dry for a month. I restock within 5-7 days of filling the pond with water. I restock and harvest one or two ponds every month. Worm tea is the liquid you get when you brew worm casts. I have many visitors every month, but less than 5% of them adopt my methods. They do, however, adopt my philosophy on the use of chemicals. Many of the other things that I do on my farm go against their beliefs. For example, farmers want their shrimp to grow very fast so they feed them commercial feeds soon after stocking. I believe if the PLs eat natural food at an early age, they will have stronger immune systems (http://www.youtube.com/watch?v=raQflD3QIsI). Come and visit me. I will be very happy to show you around. In the sea, two kilometers from my farm, there are many dolphins and two sea cows. They would disappear if I used chemicals in my ponds and then discharge the water to the sea when I harvested. Thank you for interest in my farm. My background is in engineering, and it is very difficult for me to tell my story in English. There are many details about my system that I have not reported here, so don’t try to duplicate my methods until you have a fuller understanding of them. You might damage your crop.
Kanisorn Tanthien (firstname.lastname@example.org): Hi again, this video shows a Capitella species [a polychaete worm] that thrives in sludge composted with fermented rice bran. Someone once said, “Waste is a gift from God”. I agree with that.
Olivier Decamp (email@example.com): Hello, click on the following link for a paper on the synergy between Capitella and bacteria for the degradation of organic matter:
Sources: 1. The Shrimp List (a mailing list for shrimp farmers). Subjects: EMS, EMS Impacts in Thailand, and Capitella. Tuesday, January 22, 2013. 2. Summarized by Bob Rosenberry, Shrimp News International, Friday, February 1, 2013.
The Economic Impact of EMS
Thailand: In 2012, the drop in Thai shrimp exports to the United States is on track to be the greatest ever, and will represent the lowest volume sold to the USA in nearly ten years. The primary cause for the drop appears to be the outbreak of EMS, Early Mortality Syndrome. Source: Seafood.com (an online, subscription-based, fisheries news service). Editor and Publisher, John Sackton (phone 1-781-861-1441, email firstname.lastname@example.org). Analysts Report Thai Shrimp Farmers Sanitizing Ponds for Two Months to Combat EMS. John Sackton. July 22, 2013.
Source: United States Department of Agriculture Website. Aquaculture Data. Economic Research Service. U.S. Shrimp Imports, Volume by Selected Sources [downloads as an Excel table]. David Harvey (phone 1-202-694-5177, email email@example.com). January 16, 2013.
Thailand: Bualuang Securities, a financial services company in Thailand, said that there was a slowdown in farmed shrimp production in Thailand during the fourth quarter of 2012, because between 15 and 20 percent of shrimp farms were affected by the outbreak of EMS.
As a first step, shrimp farmers have decided to completely stop the production of shrimp for two months, while the farms are disinfected!
The outbreak is more devastating than previously thought and is expected to affect shrimp production into 2013. This will have a negative effect on the shrimp business of Thailand’s Charoen Pokphand Foods (CPF), where shrimp accounts for 12% of the company’s total revenues (6% from feeds, 4% from farming and 2% from processed and cooked products). CP told its shareholders that the outbreak situation should ease in the second quarter of 2013. Source: FIS United States. Shrimp Disease Outbreak Puts Dent on Charoen Pokphand’s Net Profit. Natalia Real (firstname.lastname@example.org). January 24, 2013.
China/Ecuador: Omarsa, an Ecuadorian shrimp farm, has seen its sales to China, one of four countries in Asia that have been hit with EMS, grow dramatically since the onset of EMS. In 2011, Omarsa produced $86 million worth of shrimp, with only 10% going to China. In 2012, however, it produced $110 million worth of shrimp, with 40% of it going to China, said Sandro Coglitore, Omarsa’s managing director. In 2013, Coglitore hopes production reaches $120-$125 million, with even more sales going to China and other Asian nations. At the same time, he said sales to Europe and the USA were dropping. Sales to Europe represented 42% of Omarsa’s business in 2011, but slipped to 27% in 2012. Similarly, the USA market made up 28% of sales in 2011, but only 19% in 2012.
Coglitore said, “We have invested in 175 hectares of new farms to offset about 100 hectares we are returning in a mangrove reforestation program, so at the end we will be a little bit over 3,000 hectares again.” He also said, “...we built a 1,000 pallet coldstorage, expanded a new de-heading area with three graders and are installing a brine spray freezing tunnel, with an investment of about $5 million.” The disease problems are “definitely” understated by Thai and Vietnamese producers, he said. “Lots of new customers are calling and visiting. Everybody wants to have a foot in Ecuador.”
For 2013, Omarsa plans to increase its production of value-added products and to expand into other markets. It has long been a champion of organic and certified shrimp, and 2013 could be a big year on demand, “as disease seems to be affecting...some of the other organic producers in the world”, said Coglitore. Source: Undercurrent News. Editor, Tom Seaman (email@example.com). Ecuadorian Shrimp Firm Sees Massive Sales Boost from China. Tom Seaman. January 30, 2013.
Vietnam: In 2012, shrimp farming was heavily hit when up to 100,766 hectares of ponds were lost to EMS. According to Directorate of Fisheries, 45.7 percent of shrimp farms in Vietnam faced EMS. The whitespot and yellowhead viruses also caused problems. Source: Vietnam Seafood News. Ten Highlights of Vietnam Fisheries Industry in 2012. #7. Shrimp Farming Was Badly Affected by Early Mortality Syndrome (EMS). January 29, 2013.
Vietnam: In January 2013, in Ca Mau, Soc Trang and Bac Lieu provinces, three of the leading shrimp farming provinces in the Mekong Delta, shrimp prices jumped by around $0.48 a kilogram—when processors were not able to find product. Source: Vietnam Seafood News. Raw Shrimp Price Soars. January 31, 2013.
EMS Spotted in Silicon Valley, California, USA
United States: Imagine my surprise when this vehicle sped by me with siren screeming and lights flashing. In Silicon Valley, EMS stands for Emergency Medical Service.
Dr. Donald Lightner Thinks EMS Is Infectious
At the recent World Aquaculture Society Meeting in Nashville, Tennessee, USA (February 21-25, 2013), Dr. Donald Lightner, the famed shrimp disease expert from the University of Arizona in the United States, gave a presentation on what his laboratory has learned about EMS (Early Mortality Syndrome)—so far. He concluded:
“The disease is idiopathic; we really don’t know if it’s infectious or toxic, but all indications are that it’s infectious. All the work that we’ve done so far keeps pointing toward the very likely idea that it’s an infectious disease and not something from an environmental toxin. ...We don’t think Vibrios are the primary agent of the disease because they only become dominant as opportunistic pathogens in the terminal phase.”
“We tested a number of the feeds from some of the affected farms that have this disease, and feed doesn’t seem to have anything to do with it.”
“Early on, cypermethrin and similar pesticides that are used to kill vectors for whitespot were suspected as a cause of EMS. My lab spent quite a bit of time looking at them in static renewal bioassays, even adding them to the soil in different concentrations all the way from just a few parts per million up to several hundred parts per million and we couldn’t kill shrimp in static renewal bioassays.”
“The tests for infectious agents have been mostly negative to date. EMS is apparently not caused by a virus. Bacteria—that’s still up in the air. It’s not caused by a parasite. So most of our work in this area has been negative to date. What we plan to do in the future...we want to work in an area called metagenomics where we can compare bacterial populations from EMS affected and unaffected shrimp. We have a few interesting bacteria that we’ve isolated from shrimp that have EMS that we want to do some challenge studies with in the lab to see if possibly some of these might be related to the disease.”
Dr. Lightner also reported:
• The first cases of EMS occurred in southeastern China in 2009. In 2010, it was discovered in the Mekong Delta area of Vietnam, and in 2011 it showed up in peninsular Malaysia and then in eastern Malaysia on the island of Borneo. Eastern Thailand was hit in 2012.
• EMS affects Penaeus monodon and P. vannamei.
• The disease has two phases: acute and terminal. The acute phase begins with the deterioration of the hepatopancreas. Vital cells die and are sloughed off, and the hepatopancreas shrinks to half its normal size. As the disease progresses to the terminal phase, the hepatopancreas turns pale—yellow to white—with black spots and streaks. When removed, it does not squash or smear like a healthy hepatopancreas. The terminal phase is characterized with massive amounts of Vibrio harveyi and V. alginolyticus.
• There are no molecular tests for EMS, limiting diagnosis to histopathology.
Acknowledgements: Dr. Lightner said: “OIE [Office International des Epizooties] sent me to Vietnam a couple of times to work on this disease. The Department of Animal Health in Vietnam helped a lot with local arrangements. We’ve been funded by the Uni-President Feed Company in Vietnam and the Minh Phu Seafood Company in Vietnam. CP Foods in Thailand helped us with some of the work. The World Bank and the Global Aquaculture Alliance also helped. And most recently, we got help from the Food and Agriculture Organization of the United Nations.”
Rumors and Speculation: Among the shrimp farming community at the WAS Meeting in Nashville, EMS was a hot topic in the hallways and the trade show. Rumors and speculation about what was causing it abounded. In 2012, EMS caused losses of hundreds of millions of dollars for the shrimp farming industry in China and Southeast Asia. If a cure is not found, it could cost the industry a billion dollars in 2013. If it spreads to the rest of the shrimp farming world, who knows what the consequences will be?
There are no accurate statistics on how hard the industry has been hit by EMS, and many mortalities caused by the whitespot virus and other viral and bacterial diseases have probably been misdiagnosed as EMS. Vietnam appears to have been hit the hardest with up to 80% of its farms affected. In southern China, 60% of the shrimp farms may have been affected; in Malaysia, 50%. In Thailand, 20% to 30% of the shrimp farms may have been hit. There are also unconfirmed reports of EMS in southern Thailand near the border with Malaysia and on the island of Sumatra in Indonesia, around Medan, which is across the Strait of Malacca from Malaysia.
Sources: 1. The World Aquaculture Society Meeting in Nashville, Tennessee, USA (February 21-25, 2013). Emergence of a New Disease in Southeast Asian Shrimp Farms. Donald Lightner, Rita Redman, Carlos Pantoja, Brenda Noble, Linda Nunan and Loc Tran. February 25, 2013. 2. Bob Rosenberry, Shrimp News International, February 26, 2013.
Thai Website Reports on EMS
Shrimp News: The Asia press has been amazingly quiet about Early Mortality Syndrome (EMS), which has probably already caused over a billion dollars of losses for shrimp farmers in China and Southeast Asia. The Bangkok Post, the leading English language newspaper in Thailand, has not reported on EMS, and the Thai Department of Fisheries, a strong advocate of shrimp farming in Thailand, has not issued any English language reports or updates on EMS. Vietnam, which may have been hit the hardest by EMS, has two English language fishery websites, and neither one of them has even mentioned EMS. Not a peep out of Malaysia either, and China, where EMS started, has been equally quiet.
The following report on EMS is from Coconuts Bangkok (see Source below), a website that reports on Bangkok news:
Many shrimp ponds in Chanthaburi Province and throughout Thailand remain bone dry at this late point in the season because of fears of EMS (Early Mortality Syndrome). Typically, prawn farmers in Chanthaburi stock their ponds in January or February, with the intention of harvesting that crop just before April’s Songkran holiday. This year, however, things have turned out differently. “Only 30% of all farmers have started stocking,” says Chakarin Pecharoen, Chairman of the Chanthaburi Shrimp Farmers Club. ....“I have a deep feeling that the production in this first quarter might turn out to be something very horrible.”
Reports of EMS first surfaced in 2009 in China, where farmers noticed that their prawns had begun dying en masse, without any identifiable cause. By 2011, shrimp farms in China’s Hainan, Guangdong, Fujian and Guangxi provinces were suffering losses as great as 80%. From China, EMS made the leap to Vietnam and to Malaysia, where it left similarly massive swathes of devastation. In 2011 and 2012, EMS wreaked havoc on Vietnam’s shrimping industry. In the month of June 2011, 330 million shrimp died in Tra Vinh Province alone. In Malaysia, EMS struck in 2010, displaying a similar pattern. Between 2010 and 2011, its commercial prawn industry had a year-on-year decrease in production of roughly 42%.
In Thailand, “It’s a huge phenomenon,” says Daniel Gruenberg (see Source below), CEO of Sea Garden Foods, an aquaculture and shrimp farming company in Chonburi Province. “Just to give you a measuring stick, I had some friends that sell [shrimp feed] and if they look at their year-on-year feed sales, they’re down 70% to 80%. It’s massive.”
Dr. Putth Songsangjinda, Director of the Marine Shrimp Culture Research and Development Institute, says, “The real problem is panic among shrimp farmers. With farmers delaying their stocking, it could adversely affect Thailand’s whole shrimp production.”
For Thailand’s billion-dollar shrimp farming industry, these drops in production could prove catastrophic. The country’s shrimp exports are already in a less-than-ideal state, having suffered steady declines since their peak in 2000. With a 26.7% year-on-year drop in production between 2011 and 2012, the industry is ill positioned to withstand further shocks. Though contained for the most part to eastern Thailand, outbreaks of EMS have begun to show up in southern provinces as well.
With so much money on the line, both shrimp farmers and academic researchers have entered a race to find the phenomenon’s cause, but so far, it remains an enigma. Authorities can’t even agree on whether or not it’s a disease. Dr. Putth hesitated to call EMS an epidemic because, in order for something to earn that status, its cause must be known. In the case of EMS, all scientists and farmers have to go on are its effects. EMS causes a prawn’s hepatopancreas (essentially a liver and pancreas combined) to malfunction. This in turn interferes with the animal’s ability to digest food, thereby weakening it and leaving it susceptible to disease. Shrimp typically begin dying from EMS in the first 35 days after being stocked. Though academics studying the phenomenon remain skeptical as to whether or not EMS can also affect mature shrimp, farmers such as Gruenberg insist that it can and does.
After at first assuming that a virus had caused EMS, researchers soon widened their range of possible culprits to include genetic abnormalities, bacterial infections, toxins and shifting environmental conditions. Gruenberg believes that he may have found the cause, but his experiments are still in the initial stages, and he prefaces his description of them with a caveat that they at best constitute a “working hypothesis.” He believes that selective breeding in one of the most widely farmed specie of shrimp, Penaeus vannamei, has led to the current catastrophe. By selecting shrimp for fast growth, Gruenberg contends that breeders have inadvertently selected for weak immune systems as well. With inadequate immune systems (“like an AIDS patient,” says Gruenberg) these shrimp become susceptible to infection from protozoan parasites known as gregarines, which act somewhat like a crustacean version of malaria.
Gruenberg and his team have set up a series of experimental shrimp ponds in which they are trying to save shrimp from EMS by feeding them copepods (tiny, nutritious crustaceans) that can help them compensate for ravaged digestive capabilities and weakened immune systems. “Normally if a pond starts getting EMS, within a few weeks you’re going to be getting 100% mortality,” he says, “but we were able to save about 50% of the prawns at [the experimental] pond. So that opened our minds to nutrition as one possible solution.”
When asked about how bad things could get if the EMS outbreak continues, Chakarin, Chairman of Chanthaburi Shrimp Farmers Club, responds simply, “I dare not say.”
Sources: 1. Coconuts Bangkok (Bangkok’s Local News and Reviews Website). Thailand’s Shrimps Are Dying En Masse, and No One Can Figure Out Why. Shane Danaher and Praj Kiatpongsan. March 17, 2013. 2. Email from Daniel Gruenberg (firstname.lastname@example.org) to Shrimp News International on March 17, 2012. 3. Bob Rosenberry, Shrimp News International, March 17, 2013.
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