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September 15, 2013

Everything You Ever Wanted to Know about
SPF and SPR but Were Afraid to Ask

By Dr. Stephen Newman

 

Dr. Stephen G. Newman, Ph.D., President and CEO of AquaInTech, Inc., which provides goods and services to the international shrimp farming community, has posted a three-page article to his webpage titled Shedding Some Light on the Confusion about SPR and SPF Shrimp.  It’s the first article in a list of twelve free articles on aquaculture, pond management, equipment and disease control that appear on his site.  SPR stands for “specific pathogen resistant” and SPF stands for “specific pathogen free”.  Here are some excerpts from his article on SPR/SPF:

 

Only animals that are produced and held in nuclear breeding centers and that have gone through the modified ICES  Protocols (The International Council for the Exploration of the Sea) can be considered to be true SPF.  As soon as these animals leave a biosecure environment they cannot be considered SPF any more.  Some argue that if they are still negative for the presence of the pathogens on the list that they are still SPF.  This is not the case.  It is well documented that the virus (and its many variants) that causes WSSV can become dormant in animals.  They are PCR negative for the virus.  Some have argued that geographic isolation is sufficient as the first SPF animals were produced in Hawaii, United States, an area that one would consider to be geographically isolated.  It is documented that animals from Hawaii have moved TSV, WSSV and IHHNV into areas where they did not exist before.  Many companies buy SPF broodstock and then produce postlarvae (PLs) under conditions that are not truly biosecure.  They then sell the PLs as SPF.  As soon as they leave a completely controlled indoor environment (for example, a nuclear breeding facility), they may technically still be SPF, but they should no longer be considered as such.

 

In the early days of SPF, there was a lot of skepticism about the concept.  Although a reliable and proven concept in agriculture, it was slow to catch on in shrimp farming.  In areas where there was still a heavy reliance on wild seed many reported that SPF animals did not fare as well on the farm as wild seed.  Companies producing SPF animals struggled.   Things changed when trials showed that SPF Penaeus vannamei fared much better in a multitude of environments where seed derived from wild P. monodon broodstock were in use.  It became widely accepted that SPF vannamei could be grown profitably and were less prone to a range of disease problems than PLs produced from wild broodstock, even if the wild broodstock was PCR screened monodon.  This began the switch from monodon to vannamei farming.  There are other reasons for the switch, but the availability of true SPF vannamei was the catalyst.

 

Specific pathogen resistant (SPR) is being used in a manner that connotes an absolute in the minds of many farmers, much as the term SPF was when these animals first appeared.  Even if animals tolerate high levels of exposure to a pathogen under controlled conditions, this says nothing about what happens when stress and pathogens are involved.  When WSSV first hit Panama, many large farms were seeing horrific mortalities.  Shrimp were dying in huge numbers within days of exposure—many of them turning dark red.  In some cases, mortality rates reached 90 percent.  However, a farm with four small ponds in the middle of this area was unaffected, and its shrimp grew well.  Although the shrimp were WSSV positive by PCR, the owner did an excellent job of managing stress, and they never developed the disease.

 

Many savvy farmers understand now that WSSV infected shrimp in well managed and stress free environments do not die from WSSV.  There is a very strong correlation between the overall stress that the shrimp are under and the presence of both obligate and opportunistic pathogens.  Shrimp can carry the virus without becoming visibly ill from it.  That does not mean that they are SPR.

 

Information: Stephen G. Newman, Ph.D., President and CEO, AquaInTech, Inc.,  Lynnwood, Washington 98037,  USA (phone 1-425-787-5218, email  sgnewm@aqua-in-tech.com, webpages www.bioremediationaquaculture.com and  www.sustainablegreenaquaculture.com).

 

Source: AquaInTech’s Website.  Shedding Some Light on the Confusion about SPR and SPF ShrimpWebsite Visit on September 13, 2013.

 

Shrimp News: If you have information on your website that you think would be beneficial to the international shrimp farming community, please send me a link to the specific page that it’s on, and I’ll consider excerpting information from that page for my website and then linking to the page so that readers can view the full report (bob@shrimpnews.com).

 

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