Abstract
Shrimp Improvement Systems (SIS) operates a selective breeding program for Whiteleg shrimp(Penaeus vannamei). A sector of the breeding program conducts disease trials to test shrimp for resistance against specific pathogens. To ensure infection of subjects during trials, first a preliminary LD50 trial is conducted for each pathogen to determine the dosages administered during selecting breeding disease trials. The present study will present the results of the preliminary LD50 trial conducted on an unidentified strain of White Spot Syndrome Virus(WSSV). Two different lines (R & G) of shrimp were subject to four different treatment levels of WSSV and observed for two weeks. Average survival rates throughout the trial, for each treatment, were used to construct an LD50 curve for both lines. Using the LD50 curves,appropriate doses for future trials were determined. Samples collected throughout the trial were also subject to PCR testing to investigate if shrimp were tolerant or resistant to WSSV. Results showed that survival rates decreased as exposure to the virus increased. It was found that the R line had much higher survival rates than the G line for all treatments, except one. Treatment levels for future trials were determined to be 30% biomass for the R line and between 15-30% for the G line. No trends were observed within the PCR data regarding tolerance versus resistance.