アメリカにおけるエビ類のウイルス病に対する防除対策

Viral diseases have severely impacted many of the penaeid shrimp farming industries of the world causing significant production and economic losses. Nearly 20 distinct viruses, or groups of viruses, are known to infect penaeid shrimp. Viruses belonging to the WSSV, MBV, BMN, HPV, IHHNV, and YHV groups have been important pathogens of cultured shrimp in Asia and the Indo-Pacific regions, while TSV, IHHNV, and BP have been the principal viruses of concern in the Americas. Numerous strategies have been attempted for the control of viral diseases in penaeid shrimp aquaculture. These strategies range from the use of improved culture practices (i.e. where sources of virus contamination are reduced or eliminated, sanitation practices are improved, stocking densities are reduced, etc.) to stocking “specific pathogen-free” (SPF) or “specific pathogen resistant” (SPR) species or stocks. In the Americas many strategies have been employed in efforts to reduce production losses due to the enzootic viruses IHHNV, BP, and TSV. Improved husbandry practices have been successfully employed for the control of BP, and for nearly a decade, this virus has seldomly been reported as an economic constraint to successful shrimp culture.<BR>Until recently, the popularity and use of the relatively IHHNV resistant species Penaeus vannamei, in preference to the culture of the more IHHNV susceptible P. stylirostris, was characteristic of the shrimp farming industries of the Americas. The popularity of P. vannamei began to decline when TSV emerged as a very serious pathogen of this species in 1992 and then spread to virtually all of the shrimp growing regions of the Americas during the ensuing four years. Because P. stylirostris was found to be innately TSV resistant, two domesticated, genetically selected SPR strains of this species, which are resistant to IHHN disease, are currently being developed and marketed in the Americas. In some regions, these SPR stocks of TSV and IHHNV resistant P. stylirostris are replacing P. vannamei stocks in culture. Other shrimp farming interests are using wild or domesticated stocks of P. vannamei that show improved resistance to TSV. While resistance to TSV was used as a selection criteria for the domesticated stocks of P. vannamei, natural selection for TSV resistance appears to be occurring in wild stocks where TSV has been enzootic for several years. The same selective process for IHHNV resistance seems to be occurring in some wild stocks of P. stylirostris.