Volume 1-7  December 2020

Season’s Greetings!  I want to thank our customers for continuing to support us in these difficult times and I wish all of our readers a joyous and happy holiday season.  Next year at this time Covid 19 will be in the rearview mirror for most of us, hopefully.  

On January 1st, 2021 we will be posting an updated website.  Please bear with us as we integrate the changes.   Customers will be offered the opportunity to log in to access some additional information (preprint publications, etc.) prior to being published.

We are looking for distributors that can sell private label products, etc.  Contact us if you are interested. 

Aerial view of a shrimp farm on Puna Island

COVID 19 THOUGHTS

The foremost topic on most peoples minds today is Covid 19 and when it will no longer be impacting virtually every sector of the global economy. Those countries with populaces that are not in a position to argue with government dictates have been able to moderate the impact to a large degree.    While some would argue that their approach is draconian this is not even remotely relevant.   They did what needed to be done and continue to do so recognizing that this is a war with many battles. It appears that much of the rest of the world is  less than competent when it comes to matters of this nature; ignoring the potential severity of what is as of yet a largely uncharacterized never before seen pathogen.  We all should be grateful that this disease is what it is and not something like the Measles which is many more times virulent or Ebola which can kill in a very few short days.   If it were then the world, given the reaction to Covid 19, humanity would face the prospect of being pushed back into the dark ages.   No amount of printing of money would prevent massive deaths on a scale never seen before.    There are some who will tell you that this is actually inevitable.   Those countries with the best control of Covid 19 learned lessons from MERS and SARS 1.  Being prepared is essential.  This applies to aquaculture every bit as well.  This requires stockpiles of essentials and a mechanism that allows for a large-scale rapid response to evaluate the many potential drugs and chemicals that could be helpful and to develop vaccines.    

When there is a new disease that has never been seen before there is much more not known than known.   Fortunately humanity is at a point technologically where the scientific method allows for rapid identification and the development of highly sensitive tools to determine where the pathogen is, who is infected, etc.  Vaccines cannot always be developed quickly and easily.   Some pathogens (such as the influenza virus) cannot (yet) be the subject of universal vaccines that protect against all variants without decades of research.   Others, which appears to be the case with SARS 2 Co-V appear simpler,  although humanity will not know for months to come if vaccine induced immunity is long lasting and effective. 

The failure on the part of many governments to treat appropriately and rapidly using time honored methods to quash the spread is what we are seeing on a global scale. Given the current estimates of mortality, between 0.5 and 1%, roughly five to ten times more deadly than the seasonal flu, globally we would see between 40 and 80 million deaths occurring in a very short time frame if the virus spreads uncontrolled.   

SHRIMP VIRUSES

PLs in Brazil

It is interesting to note that with many of the shrimp viruses we see similar failures on the part of governments to control the spread.   The tools exist to significantly reduce the impact, but the will is not there.  Forced PCR screening of all broodstock, strict enforcement of the movement of non-tested animals, a universally agreed upon definition of what a safe nucleus breeding center (NBC) is, etc. are all elements of this.   If one looks at the current state of the shrimp farming industry it is quite clear that the lessons that should have been learned have not been.

The power of being able to screen for all of the DNA and/or RNA present in a given animal has revealed some very interesting things.   We know that invertebrates carry many viruses, most of which are not characterized (and may never be).    The number is easily in the hundreds if not more.   This is not unusual and should not come as a surprise.   Viruses are ubiquitous.    When a previously unreported virus is reported one can watch it spread.   This is true for most shrimp pathogens.   The reasons for this are many and the solutions, while apparent, do not seem to be  all that easy to achieve.   We also have discovered that there are many, likely millions, of bacterial and like species that have not been characterized and that cannot be grown in culture.   Do not be fooled into thinking that we understand what is going on in any manner but a very broad brushstroke. 

Why do I believe that viral diseases are going to continue to cause problems for the shrimp farming industry?   Failure to understand what a  NBC's role is in ensuring that pathogen carrying animals are not being moved is part of this.   NBCs in shrimp farming should not be allowed to bring in animals from the outside without each animal being tested, held for a full life cycle in quarantine, etc.  NBCs for shrimp must be operated based on the biology of the animal.   These are not pigs or chickens.   Many   companies selling broodstock and it seems, most regulators, have no clue what an NBC is and how it works.   

Another important reason for the continued spread of what should be preventable diseases is that shrimp farming in large part is not a highly technical process.   Science is often ignored and pseudoscience dominates.  All one has to do to see this first hand is to look at the types of products that farmers are being sold.    

Biosecurity has become a meaningless word.  Much as the term probiotic, eco, green, etc.  Infected animals are moved across borders all the time.   Farmers are sold  many useless tools and convinced that they work because of coincidence or flamboyant marketing.    There are no magic bullets that will fix problems that are a result of the very nature of how shrimp farming operates.

Intensive shrimp farm in Phu Yen, Vietnam

The year 2019 was a great year for shrimp farming, the best ever.  Growth in demand fueled growth in production.  Actual production levels are difficult to get at.   Conservative estimates are more than 4 million MTs. There was not enough shrimp, it seemed, to go around.  The industry was giddy  from unprecedented profits. Most shrimp farming countries were planning on expanding production in response and the groundwork was being laid for this.   With the advent of Covid 19 these plans were put on the back burner.   The service sector was hit very hard and demand through this avenue dropped precipitously.   The retail sector was hit as well although as the year progresses the retail sector is taking up some of the slack.   Global production will likely drop by 20 to 30% in 2020.  Some countries will fare better than others with a great deal of volatility being the norm in price and production levels.  This should stabilize going into 2021 as vaccines against Covid 19 become available, and strictures on gathering in crowds are lifted.    

The Covid 19 threat is unique in the sense that this has never occurred  in the modern era.  That is,   a new virus that humans have not ever been exposed to and that infects large numbers of people with low overall levels of mortality, is omnipresent.   

Shrimp farming has been dealing with a seemingly endless onslaught of diseases.  There are several critical diseases that are continuing to spread globally.   Notably, the fungal pathogen Enterocytozoon hepatopenaei (EHP) remains a global threat.   This is a spore forming pathogen that ironically was initially spread globally in stocks that came from a  NBC.   If the NBC had never allowed any biological materials, including shrimp,   from outside to ever enter the facility, this  would not have happened.  Ironically as well, the animals in the NBC were infected some time before a small change in a staining protocol explained why there were performance issues during growout with no apparent cause and the presence of EHP.  White feces disease which appears to be linked in some manner to EHP is also spreading.   The etiologic agent for this has yet to be identified although there are some reports that suggest that a vibrio or  possibly some as of yet uncharacterized bacterial pathogen  could be involved.   Another virus (sadly not the only one) has also been reported and it is spreading as well.

The following is translated from a Chinese article of a presentation given in May of this year.   I have edited it for clarity.  This is among a number of new diseases that have  appeared over the last few years. 

PvNV infected shrimp

Recently, “glass” shrimp fry have been reported in Eastern Guangdong, China, mainly due to the difficulty of (keeping PLs alive) standard seedlings, low success rate, shrimp jejunum and jejunum, transparent body color, and easy death during the process of standardization. This is not a new disease. “Glass” shrimp seedlings appeared before 2019 and the incidence has increased annually since then.  This year, 2020, is particularly serious, with an incidence rate of around 70%.

Researchers identified a small RNA virus in the 'glass' shrimp.  They purified the virus particles, completed genome sequencing, developed a PCR detection method, and also completed the required artificial infection experiment (confirming Koch’s postulates as Rivers addenda are not universally applicable).  This is a newly described small RNA virus, temporarily named hepatopancreas and digestive tract necrosis virus (HINV).  

As is common the infected animals in the field were also carrying other potential pathogens, including but not necessarily limited to the white spot syndrome virus (WSSV), infectious subcutaneous and hematopoietic necrosis virus (IHHNV), and EHP were detected in diseased shrimp, uninfected shrimp (PCR negative for HINV) and broodstock. Decapod rainbow virus 1 (DIV1-formerly called SHIV) and highly pathogenic Vibrio parahaemolyticus strains have not been detected.   

HINV is a (newly discovered) viral disease.   It appears to be highly pathogenic to prawn larvae but not as much to shrimp in growout.  Infected shrimp in the field die slowly.   The exact route of infection in the wild remains to be determined.   More experiments are still underway.  The main tissues and organs that the virus infects are the hepatopancreas, digestive tract, and carapaces epidermis. Generally mortality begins two days or so post exposure with  a mortality rate on the fourth day approaching 100%.   It may be carried by broodstock or spread through the water.   HINV has been detected in healthy shrimp seedlings albeit at low levels. Broodstock must be screened for the virus and no infected animals used.  There are other contributing factors as well, including high density culture and inadequate water treatment.  Prevention starts with the use of SPF broodstock and PLs and stress reduction.    Improving water quality and avoiding polyculture are other areas that can impact susceptibility.

He ended with an admonition.  There are other as of yet uncharacterized pathogens affecting farmed shrimp in China and elsewhere.  

Biosecurity is critical for sustainability.  This does not automatically mean that SPF animals are the solution.   SPF does not mean that a population is necessarily free of a given pathogen.    This can only be established with certainty via the use of NBCs.  When properly configured, these are 100% biosecure production facilities where the founding broodstock are quarantined and their offspring are the focus of testing, etc.  The facility is designed to ensure positive air flow rates, that no personnel move between sections, that no contaminated feeds enter the facility, that no animals ever enter the facility, etc.  These are strict guidelines that can ensure that the animals contained within are free of all known pathogens and are held in a manner that ensures that they are also free of any unknown pathogens by virtue of extreme levels of screening, stress testing, etc.  

The vast majority of companies that claim to have these types of facilities do not.  As soon as one element is impacted the population should NOT be considered to be SPF.   This is not the same as moving animals from one way (nothing in) into biosecure SPF holding facilities for the next steps.

NBCs stocking healthy strong PLs that are free of all known pathogens are critical for the development of a sustainable industry.   One tiny misstep is that all that it takes to undo this and spread diseases far and wide, often unwittingly but far too often deliberately.   One cannot make the excuse that one has screened animals using the AFS Blue Book tables for certain pathogens and that this is all that is needed to protect one’s stocks.  Statistical screening does not equate with an SPF production facility in the absence of the aforementioned.  Developing SPF stocks entails a process that must be followed.  If it is not then the animals, by definition, should not be considered to be SPF.   

Biosecurity is defined as the sum of all of the protocols put in place to minimize the impact of disease.  They are many variants of this some quite detailed.  The bottom line is always the same.  The strategies when properly employed will result in PLs being stocked that are not carrying any obligate or opportunistic pathogens.

Aquaintech Inc. can help your realize these goals if you are willing to listen and take the needed steps.