Taura syndrome virus (TSV) has spread worldwide, causing significant economic losses since Taura syndrome was first described in Ecuador in 1992. To determine the prevalence and impact of TSV infection on the shrimp farming industry in Taiwan, Pacific white shrimp Litopenaeus vannamei B. were collected from 220 farms between 2004 and 2006 for viral detection by reverse transcription polymerase chain reaction. Data showed that the overall TSV prevalence rate was 20% (43/220 farms). Comparing shrimp growth stages, TSV prevalence rates were 4% 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% in juvenile 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 appendages had red pigmentation, which is characteristic of TSV infection. Of shrimp with pathological lesions, 100% had lesions on tail fans, 88% on appendages, and 80% in gills. Sequence comparison using the TSV VP1 (structural protein) gene showed that 9 isolates from the farms had 92.3 to 99.5% nucleotide sequence identity with strains in the GenBank database from Taiwan (AF406789 and AY355310) and Venezuela (DQ212790). This is the first broad epidemiological study of TSV infection in L. vannamei in Taiwan.
KEY WORDS: Taura syndrome virus · Litopenaeus vannamei · Taiwan
Resale or republication not permitted without written consent of the publisherDis Aquat Org 97: [17][18][19][20][21][22][23] 2011 fection of L. vannamei by TSV has resulted in cumulative mortality rates of 40 to 90% .First isolated from white shrimp farms near the Taura River in Ecuador in 1992, TSV is a nonenveloped, single-stranded RNA virus classified as Cripavirus in the family Dicistroviridae (Mayo 2002, Wertheim et al. 2009). The icosahedral virion is roughly 32 nm in diameter, and the genome is approximately 10 kb long. TSV spreads rapidly within shrimp populations. Insects and birds may also contribute to the spread of the virus. The intestinal tract of Trichocorxareticulata may harbor TSV , and gulls can carry and pass the virus in their feces (Garza et al. 1997). Infection of TSV can be separated into 3 phases. The acute phase (Days 1 through 7 post infection) is characterized by lethargy and loss of appetite. The most prominent characteristic of TSV infection is red pigment deposition on the surface of the shrimp, generating a dark-pink appearance, and the tail fan and appendages will appear especially red , Tu et al. 1999. Most infected shrimp will die if ecdysis takes place during the acute phase. During the transition phase, typical TSV lesions are being resolved and black spots can be observed. During the chronic phase of the disease, shrimp appear grossly normal (Hasson et al. 1999), and horizontal transmission of TSV may occur (Overstreet et al. 1997).We examined the epidemiology of TSV in Litopenaeus vannamei in Taiwan. Dia...
