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Diseases of Aquatic Organisms

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DAO 65:75-78 (2005)  -  doi:10.3354/dao065075

Effect of chronic Taura syndrome virus infection on salinity tolerance of Litopenaeus vannamei

Jeffrey M. Lotz1,2,*, Lesber Salazar Anton1, M. Andres Soto1

1Department of Coastal Sciences, The University of Southern Mississippi, Gulf Coast Research Laboratory, PO Box 7000, Ocean Springs, Mississippi 39566-7000, USA
2Present address: Department of Biology, Texas A&M University at Kingsville, Kingsville, Texas 78363, USA

ABSTRACT: Taura syndrome virus (TSV) is one of the most important shrimp viruses affecting farmed shrimp worldwide. After an acute phase during which the likelihood of mortality is elevated, infected shrimp enter a chronic phase during which shrimp appear to resume normal behavior and display no gross signs of infection. This study was designed to determine if chronically TSV-infected shrimp Litopenaeus vannamei are compromised by the infection. Specifically we investigated whether chronically infected shrimp could tolerate a drop in salinity as strongly as uninfected shrimp. The study consisted of 3 trials that compared survival of uninfected and chronically TSV-infected L. vannamei after drops in salinity from 24 ppt to salinities varying from 18 to 0 ppt. Logistic regression detected a significant effect of TSV infection on survival of chronically infected shrimp (p < 0.05). Salinity drops from 24 ppt to 3 and 6 ppt resulted in statistically different survivals (p < 0.05). Survival rates were similar among groups for salinity drops to greater than 6 ppt or less than 3 ppt. Salinities at which 50% of the shrimp died (LC50) were 3.06 ppt for the uninfected and 6.65 ppt for the chronically infected groups. Moreover, histopathological analysis of chronically infected shrimp that were moribund or recently dead showed no signs of having reverted to the acute stage of the disease. These results suggest that chronically infected shrimp are not able to tolerate a salinity drop as strongly as uninfected shrimp.

KEY WORDS: Taura syndrome virus · Litopenaeus vannamei · Shrimp · Virus

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