Dual infections of IMNV and MrNV in cultivated Penaeus vannamei from Indonesia

Whitening of muscle tissue in farmed whiteleg shrimp Penaeus (Litopenaeus) vannamei can result from stress-induced muscle cramps and from viral infections caused by infectious myonecrosis virus (IMNV) or Penaeus vannamei nodavirus (PvNV). A similar viral-induced whitening of muscles can be caused in the river prawn Macrobrachium rosenbergii and in larvae of the penaeid shrimp Penaeus (Penaeus) monodon and Penaeus (Fenneropenaeus) indicus by a mixed infection with Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV). Here we describe mixed infections of IMNV and MrNV in juvenile cultivated P. vannamei from Indonesia, detected by nested RT-PCR and immunohistochemical analysis. Muscle lesions in the dually-infected shrimp gave positive immunohistochemical reactions for both IMNV and MrNV, while connective tissue in the same samples gave positive reactions for MrNV only, indicating some differences in tissue specificity between the two viruses. Although it is not known whether the dual infections are more lethal to shrimp than single IMNV infections, this is possible since earlier work has shown that MrNV alone can increase mortality of P. vannamei under stress. (C) 2012 Elsevier B. V. All rights reserved.