A laboratory challenge method for estimating taura syndrome virus resistance in selected lines of pacific white shrimp Litopenaeus vannamei

Among the strategies being developed to improve survival and harvest yields in the farming of Pacific white shrimp Litopenaeus vannamei is breeding domesticated family lines and the selection for further development of those lines that demonstrate resistance to Taura syndrome virus (TSV) challenge in the laboratory. A standardized laboratory challenge method for measuring TSV resistance by per os exposure to the virus, relative to a reference stock of L. vannamei, was developed and used to screen a total of 176 family lines provided by five different companies over a period of several months. All challenged shrimp were exposed to TSV per os by feeding minced TSV-positive shrimp carcasses at similar to 10% of the shrimp biomass once per day for three consecutive days. Studies were carried out for a minimum of 14 d from the first day (day 0) of exposure to TSV. The survival rates obtained following TSV challenge of the selected L. vannamei families ranged from 0% to 100%, with a mean of 31 %. The reference line of L. vannamei ("Kona line") gave survival rates of 0% to 37% with a mean of 13%. The results of the present study demonstrate that the use of a relatively simple laboratory challenge procedure provides a mechanism to evaluate and compare resistance to TSV among selected L. vannamei families and to predict the performance of selected stocks in farm environments where TSV is enzootic.