We analysed 20 boxes of, frozen imported bait-shrimp (China: Parapenaeopsis sp. and Metapenaeopsis sp.) and 8 boxes of native, frozen bait-shrimp (Gulf of Mexico: Litopenaeus setiferus and Farfantepenaeus duorarum) by RT-PCR or PCR for Taura syndrome virus (TSV), yellowhead virus/gill-associated virus (YHV/GAV), white-spot syndrome virus (WSSV) and infectious hypodermal and hematopoietic necrosis virus (IHHNV). All 28 boxes of shrimp were negative for TSV, YHV/GAV and IHHNV; 2 boxes of imported bait-shrimp were WSSV-positive by 3 different PCR assays. Intramuscular injection of replicate groups of SPF (specific pathogen-free) L. vannamei juveniles with 2 different tissue homogenates prepared from the 2 WSSV-positive bait boxes resulted in 100% mortality of the test shrimp within 48 to 72 h post-injection. No mortality occurred among injected negative control groups. Histological and in situ hybridization analyses of 20 moribund treatment-shrimp demonstrated severe WSSV infections in each sample. Oral exposure of SPF L. vannamei postlarvae, PL (PL 25 to 30 stage; ~0.02 g) to minced tissue prepared from the 2 WSSVpositive bait-lots did not induce infection, possibly because of an insufficient infectious dose and/or viral inactivation resulting from multiple freeze-thaw cycles of the bait-shrimp during PCR testing. Use of an electric drill and collection of drill-tailings (tissue from ~20 to 30 shrimp) from frozen blocks of shrimp was successfully employed as an alternate tissue-sampling method without thawing. Our findings indicate that imported WSSV-infected bait shrimp, originating from China, are being sold in Texas for the purpose of sport fishing and represent a potential threat to freshwater and marine crustacean fisheries, as well as to coastal US shrimp farms.KEY WORDS: White-spot syndrome virus · PCR · Histopathology · Bait-shrimp · Disease transmission · Biosecurity · Penaeid shrimp Resale or republication not permitted without written consent of the publisherDis Aquat Org 71: [91][92][93][94][95][96][97][98][99][100] 2006 variably staining intranuclear inclusion bodies within multiple target tissues that are readily identifiable by light microscopy and are considered pathognomonic for this disease (Lightner 1996).The first recorded outbreak of WSSV in the western hemisphere occurred among wild-caught Gulf of Mexico (GOM) Litopenaeus setiferus shortly after they were stocked in a South Texas shrimp farm in 1995 (Lightner 1996). Between late 1995 through early 1997, multiple WSSV epizootics were documented among feeder crayfish populations (Orconectes punctimanus and Procambarus sp.) at the National Zoo in Washington DC (Richman et al. 1997). Chang et al. (2001) demonstrated the presence of asymptomatic WSSV infections among wild Atlantic blue crabs Callinectes sapidus collected off the coasts of New York, New Jersey and Texas during 1997. Subsequent WSSV detection among indigenous GOM L. setiferus or Farafantepenaeus aztecus stocks occurred in , 2001 (pers. comm. P. Ostrowski, T. Varner, CE...