January 27, 2006
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Dr. Tim Flegel on Shrimp
Immunology and IHHNV
In the December 2005 issue of the Global Aquaculture Advocate, Dr. Timothy Flegel, a professor at Thailand’s Mahidol University, begins a two-part discussion on the dangers of translocating shrimp. Some excerpts:
Shrimp carry viruses that are harmless to themselves that might cause mortalities in closely related species. The failure to appreciate this fact has resulted in three major shrimp epizootics that collectively caused economic losses of several billion dollars (see IHHNV below).
Laboratory experiments in the past decade indicated that, in general, shrimp and other arthropods are capable of a specific, protective, immune-like response that cannot be explained by the current understanding of their cellular and humoral defenses.
Recent field research with shrimp and insects suggests that this protection might stem from the viral pathogens themselves. The well-known phenomenon of “defective interfering viral particles” probably plays an important role in this process, but it cannot explain the cross protection recently described for heterologous [from another species] viral infections in shrimp and insect cells. Homologous and heterologous reduction in disease severity as a result of persistent viral infections may be a key process that evolved from host/viral interactions in the arthropod line.
Other recent publications have shown that prior exposure of shrimp to inactivated viral particles or envelope proteins can protect them from lethal viral challenge for a short time. In contrast, persistently infected shrimp appear to maintain protection as long as they remain infected. One would therefore expect the protection to have specificity, as was earlier proposed; however, heterologous protection remains unexplained.
Since treatment with inactivated viruses or coat proteins runs out relatively quickly, it should not be called vaccination and compared to long-term protective, antibody-based immunological memory, such as that gained by vaccinations in vertebrates. There is no evidence that shrimp or other arthropods have a comparable defense system.
Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV) was first discovered in blue shrimp, Penaeus stylirostris, and white shrimp, P. vannamei, in the Americas in the early 1980s. It was believed to have been introduced by the importation of live experimental stocks of black tiger shrimp, P. monodon, from Asia.
It is important to understand that IHHNV was unknown before this jump from P. monodon because it generally produces no adverse effects or signs of disease in P. monodon. Often it can be detected only by using polymerase chain reaction assays.
This was the first example of a very costly epizootic caused by an unknown virus that jumped from one grossly healthy shrimp species to another. Unfortunately, the lesson went unheeded and subsequent epizootics by new viruses occurred.
Although IHHNV occurs in several species of wild and cultured penaeid shrimp throughout the world, it has been reported to cause acute epizootics and mass mortality only in P. stylirostris, especially in juveniles and subadults. In P. vannamei, it does not cause mortality but does cause reduced, irregular growth and cuticular deformities, gross signs collectively referred to as runt deformity syndrome (RDS). In spite of no mortality, commercial losses from RDS can be high.
P. stylirostris and P. vannamei that survive IHHNV epizootics can carry the virus for life and pass it on by vertical and horizontal transmission. The infected adult carriers show no signs of disease or mortalities. Vertically infected larvae and early postlarvae of P. stylirostris do not become diseased, but massive mortalities can occur in juveniles at 35 days or more. P. indicus and P. merguiensis appear refractory [resistant] to infection.
Source: The Global Aquaculture Advocate (http://www.gaalliance.org). Dangers of Viral Pathogens in Translocated Shrimp--Part I. Timothy W. Flegel, Ph.D. (Centex Shrimp and BIOTEC, Chalermprakiat Building, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand, email firstname.lastname@example.org). Volume 8, Issue 6, Page 82, December 2005.
Goa, a small state on India’s central west coast, has one government-run shrimp hatchery that serves about 200 hectares of private sector ponds. Established under the United Nations Development Program in 1992, it is closed right now because a paperwork glitch prevented the repair of its transformer. Cedric Gomes, newly appointed hatchery manager, says he expects the problem to be resolved by the end of January 2006 and that it will take around 35-45 days for the hatchery to start producing again. Though the hatchery has a 25-million [per month?, per year ?] capacity, it has never been utilized to its optimum, thus incurring losses over the years. Three years ago the government planned to lease the hatchery to a private party, but there were no takers. The farmers now buy their seed from private hatcheries across the State’s southern border.
Source: Oheraldo (website GOA, India). Benaulim shrimp hatchery left in the lurch (http://oheraldo.in/comment/reply/8665). Guilherme Almeida. January 15, 2006.
According to the Maritime and Fisheries Ministry, seven shrimp companies are suspected of importing shrimp from China and re-exported it to other countries.
[According to the Indonesian Kompas news service, the seven are PT BMI (believed to be PT Bumi Menara Internusa), PT STP (believed to be PT Suri Tani Pemuka), PT PMMP, PT KML (believed to be PT Klola Mina Laut), PT SAT, PT OG, and PT SGF (believed to be PT Seafer General Foods).]
Source: Seafood.com (an online, subscription-based, fisheries news service). Seven Indonesian shrimp exporters named as suspected of transshipping Chinese shrimp. Editor and Publisher, John Sackton (phone 781-861-1441, email email@example.com). January 16, 2006.
Shrimp Prices Firm
In Thailand, shrimp prices are expected to stay firm until the middle of 2006 because unfavorable weather conditions in the main production areas reduced production. Somsak Paneetatyasai, president of the Thai Shrimp Association, said floods affected many shrimp ponds in the South and delayed stocking. Consequently, harvesting will not take place until June or July, one or two months behind schedule. He said the resulting supply shortfall would likely push up prices.
Prices to the farmer for white shrimp currently range from $2.79 for a kilo containing 80 shrimp to $4.44 for a kilo containing 50 shrimp.
Customs Department statistics show shrimp exports from January to November 2005 totaled 260,426 tons, up 21% from the same period in 2004.
Source: Bangkok Post (newspaper, Bangkok, Thailand). IN Brief: Matichon share sale (http://www.bangkokpost.com/Business/17Jan2006_biz11.php). January 17, 2006.
CP Gets $45 Million for Indonesian Farm
The International Finance Corp said it is providing a seven-year, $45 million loan to PT Central Pertiwi Bahari, the Indonesian shrimp farm owned by Thailand’s Charoen Pokphand business group.
Founded in 1956 and headquartered in Washington, DC, USA, the International Finance Corporation, a member of the World Bank Group, promotes sustainable private sector investment in developing countries as a way to reduce poverty and improve people’s lives.
Sources: 1. Seafood.com (an online, subscription-based, fisheries news service). World Bank lends Charoen Pokphand $45 million for shrimp expansion. Ken Coons. Editor and Publisher, John Sackton (phone 781-861-1441, email firstname.lastname@example.org). January 18, 2006. 2. International Finance Corporation Website (http://www.ifc.org/about). January 22, 2006.
In response to a discussion on the Shrimp List, Durwood Dugger, a shrimp farming consultant, wrote:
The effect of temperature variation on developing shrimp larvae is often overlooked. Constant temperatures are easy and inexpensive to maintain and make a significant contribution to the bottom line.
If you do much research into the nonspecific immune system, you can’t help but recognize the importance of temperature variation on the immune system and the resulting negative impact of temperature variation on the general growth and survival in shrimp (other animals too, including us). I remember some lab work that Dr. Rolland Laramore did in the mid-1990s. He took nauplii from one spawn and randomly divided them into two groups. One group was held at an absolutely constant temperature (I think it was 28C, or perhaps 30C). The other group was subjected to plus or minus one degree variation in temperature each day. What I have before me are two vials of Rolland’s well-preserved PLs from that experiment, a vial from the constant-temperature group and a vial from the one-degree-variation group. At PL-8, the animals in the constant-temperature group were twice the size of those in the one-degree-variation group. I also believed that there were significant developmental stage differences and consequently very significant production cost differences, especially in terms of Artemia consumption and other overhead costs. Slower developing PLs consume more food and energy. I think Dr. Laramore tracked these healthier, faster growing PLs through growout conditions and found they performed at superior levels. Most of us have observed that healthy hatchery animals produce better harvests, so this would be expected. The visual impact of the 100% weight and size difference that just one degree variation made in these two batches of PLs is dramatic.
Don’t underestimate the cost of not having heaters in your larval rearing tanks. Just as important, don’t underestimate the cost of not having very accurate thermostatic controllers operating those heaters. The best heater is only as good as the thermostat that controls it. The ambient variation of the temperature in your hatchery building will also be a factor in controlling the tank temperatures. If it is highly variable, you may also have to insulate and cover your tanks. I have watched a lot of hatchery operators go through all kinds of sophisticated and expensive contortions with cure-alls and probiotic measures to stabilize production. If they don’t control the temperatures in their hatchery tanks, they fail and don’t know why. If you don’t have stable temperatures, it is likely you will never understand the effects of all the other things that you are doing to tweak your production. In the final analysis, you will have higher hatchery production costs and weaker PLs without heaters, and you will have lower production and profits in your growout.
Source: The Shrimp List (a mailing list for shrimp farmers, “email@example.com”). Subject: [shrimp] Old breakthroughs commonly ignored in hatchery practice that are proven to increase vannamei survival rate? From: firstname.lastname@example.org. January 13, 2006.
Maine-No Market for Coldwater Shrimp
This was supposed to be a comeback year for the Maine coldwater shrimp fishery. Scientists said the ocean would be full of shrimp, regulators agreed to a wide-open 140-day season, and fishermen were eager to catch and sell them. Trouble is, the market doesn’t want them anymore. “Nobody’s buying nothing,” said Branimir Viducic, the captain of the William-Lynn, a 65-foot boat.
Shrimp oversupplies worldwide, combined with a series of small and inconsistent local catches, have left fresh Maine shrimp with almost no value. Prices in Portland collapsed to ten cents a pound in early January 2006, Viducic said. With diesel fuel at $2.10 a gallon, dragging a net for shrimp these days, at least without a set-price contract with a buyer, could amount to a very expensive hobby. Viducic said he couldn’t give away the shrimp he brought home from his last trip.
Ben Lindner, manager of Fishermen’s Net, a shrimp retailer, said, “For us to get shrimp we have to contract a boat, so we’re paying more just to get it in our store.” In early January 2006, his store was selling ten pounds of whole shrimp for 89 cents a pound and one pound of shrimp meat for $4.99 a pound.
Source: Mainetoday.com (the webpage of several newspapers in the state of Maine). Shrimp market in Maine keeps shrinking (http://morningsentinel.mainetoday.com/news/local/2333712.shtml). John Richardson. January 16, 2006.
Nevada-Aquaculture America 2006-Five Shrimp Sessions
Click here to view a list of the presentations/authors/topics.
Source: Bob Rosenberry, Shrimp News International, January 20, 2006.
Washington DC-Shrimp Prices Up
Today's National Marine Fisheries Service's Shrimp Price Report shows a lot of green, indicating rising shrimp prices. Click here to check it out.
Source: Bob Rosenberry, Shrimp News International, January 27, 2006.
Washington State-Aquaculture Certification Council-Charles Woodhouse’s Column
In his November 2005 column in Fish Farming International, Charles Woodhouse says, “I will be serving as Aquaculture Certification Council’s president for the 2006 term, having been its secretary and a director for the past three years.” The Aquaculture Certification Council is a process certification program for shrimp farms, processing plants, hatcheries, and soon, feed mills.
Source: Fish Farming International (http://www.fishfarming.co.uk). All About the ACC (http://www.aquaculturecertification.org/index.html). Charles Woodhouse (www.lawyers.com/seafoodlaw). Volume 33, Number 1, Page 9, January 2006.