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May 24, 2013


Selective Breeding for Disease Resistance


From Abstract: In South America, the main pathogens that have impacted shrimp farm production are the viruses WSSV, IHHNV and IMNV and the intracellular bacteria NHP.  Since the first WSSV outbreak in 1999, Concepto Azul, a company the specializes in aquaculture biotechnologies, has implemented disease prevention and genetic selection programs in Ecuador, Panama, Peru and Brazil.  These programs have included transmission mechanisms studies for these four pathogens, showing evidence of both horizontal and vertical transmission from broodstock to offspring.  Considering that open semi-intensive farm production systems do not allow for complete biosecurity, it has been necessary to select broodstock and postlarvae resistant to these pathogens in order to improve survival as well as other traits (growth, fecundity, resistance to abiotic stress).  Using lab and pond challenge tests, the strategy has relied on exposure of all candidate broodstock to pathogens at each generation to increase their resistance.  All survivors to disease challenges are individually screened by highly sensitive and specific molecular methods (nested PCR/LAMP/qPCR/MALDI TOF TOF) in quarantine, before transfer to maturation units.  As a result, pathogen-free and resistant selected broodstock are exclusively used for production of pathogen-free nauplii and postlarvae.  In order to enhance heritability and fix characters of interest, pure line and line-breeding strategies have been carried out.  In addition, immune gene expression quantification in resistant broodstock has been studied by quantitative real-time PCR in order to understand mechanisms of resistance.


Unprecedented high levels of resistance to WSSV in pure lines from Panama (CAMACO) genetic selection program have been confirmed by a disease challenge test performed by D. Lightner in 2011.  Resistance to IMNV has also been significantly increased in Brazil (Queiroz Galvao Alimentos).  NHP and IHHNV infection rates and impact have been significantly reduced.  Survival rates in shrimp farms have recovered and surpassed pre-epidemic levels.  Comparative studies between selected and unselected lines in commercial farms generally show higher survival rates for postlarvae lines selected for disease resistance.


Information: Virna Cedeño, Chairman, Concepto Azul, S.A., Calzada Vernaza Norte, Mezzanine 10, Villa 34, P.O. Box 09-02-142-A, Guayaquil, Ecuador (phone 593-4-2284066, email, webpage


Source: The Thumb Drive Containing the Abstracts from Aquaculture 2013 (February 21-25, 2013, Nashville, Tennessee, USA).  Information: John Cooksey, World Aquaculture Conference Management, P.O. Box 2302, Valley Center, California 92082 USA (phone 1-760-751-5005, fax 1-760-751-5003, email  Shrimp Disease Prevention and Genetic Selection Programs for Resistance Against Pathogens in South America: Strategy, Results and Perspectives.  Gael Leclercq, Emmerik Motte, Virna Cedeño, Xavier Serrano, John Montaño, Carlos Mello, Benoit Diringer and Eric Mialhe.  February 2013.


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