A comparative histopathological, immunohistochemical and nested-PCR study for diagnosis of infectious pancreatic necrosis in the naturally infected cultured rainbow trout (Oncorhynchus mykiss)

Abstract

To confirm the diagnosis of the infectious pancreatic necrosis, the pancreas, liver, kidney and spleen specimens from 140 rainbow trout (Oncorhynchus mykiss) of weight ranges from 15 to 250 g were processed for routine histopathological and immunohistochemical (IHC) studies together with a nested-PCR using primers that amplify a 164-bp product. Of the 140 fish samples, 37 (26.4%) had a final diagnosis of IPN on the basis of hematoxylin and eosin staining (H&E), while 39/45 (86.6%) were positive by IHC method. With the nested-PCR, 59/140 (42.1%) fish samples were positive. The IHC and nested-PCR showed higher prevalence than histopathology (P \ 0.05). Based on the nested-PCR, as the fish weight increased, IPN positive results decreased (P \ 0.05). However, IHC method detected IPNV constantly in these weight ranges. Only IPNV serotype Sp was identified by nucleotide sequencing and immunohistochemistry, and antiserum to IPNV serotype Ab and IHNV showed negative results in IHC. This is the first comparative diagnostic study of IPN at different weight ranges in cultured salmonids.Keywords Infectious pancreatic necrosis virus Á Rainbow trout (Oncorhynchus mykiss) Á Histopathology Á Immunohistochemistry Á Nested-PCR Abbreviations IPNInfectious pancreatic necrosis IPNV Infectious pancreatic necrosis virus H&E Hematoxylin and eosin IHC Immunohistochemistry RT-PCR Reverse transcription-polymerase chain reaction TBST Tris-buffered saline with Tween

Molecular Characterization of the VP2 Gene of Infectious Pancreatic Necrosis Virus (IPNV) Isolates from Mexico

“…Based on these studies, the IPNV isolates included in this study should be nearly avirulent, with Ala, Thr, and Glu amino acid residues at positions 217, 221, and 247, respectively. However, despite the presence of Thr at position 221 in Iranian isolates of IPNV (Dadar et al 2013), the observed mortality among naturally infected Rainbow Trout fry corresponds to that caused by moderately virulent isolates (Raissy et al 2010;Oryan et al 2012;Ahmadi et al 2013). Similarly, Rainbow Trout naturally infected with MEX2-CSM-05 showed signs of infectious pancreatic necrosis, including mortality (authors' unpublished data).…”