Epidemiology and phylogenetic analysis of Taura syndrome virus in cultured Pacific white shrimp Litopenaeus vannamei B. in Taiwan

Abstract

Taura syndrome virus (TSV) has spread worldwide, causing significant economiclosses since Taura syndrome was first described in Ecuador in 1992. To determine the prevalenceand impact of TSV infection on the shrimp farming industry in Taiwan, Pacific white shrimpLitopenaeus vannamei B. were collected from 220 farms between 2004 and 2006 for viral detectionby reverse transcription polymerase chain reaction. Data showed that the overall TSV prevalencerate was 20% (43/220 farms). Comparing shrimp growth stages, TSV prevalence rates were4% for postlarvae, 24% for juveniles, 24% for subadults, 32% for adults, and 5% for brooders.Among TSV-positive farms, average infection incidence was 35% in postlarvae farms, 55% injuvenile farms, 39% in subadult farms, 31% in adult farms, and 20% in brooder farms. Notably,TSV was also detected in Exopalaemon orientis H. from 1 of 10 farms. Tail fans and appendageshad red pigmentation, which is characteristic of TSV infection. Of shrimp with pathologicallesions, 100% had lesions on tail fans, 88% on appendages, and 80% in gills. Sequence comparisonusing the TSV VP1 (structural protein) gene showed that 9 isolates from the farms had 92.3 to99.5% nucleotide sequence identity with strains in the GenBank database from Taiwan(AF406789 and AY355310) and Venezuela (DQ212790). This is the first broad epidemiologicalstudy of TSV infection in L. vannamei in Taiwan. © Inter-Research 2011.