Infectious pancreatic necrosis virus in Atlantic salmon, Salmo salar L., post‐smolts in the Shetland Isles, Scotland: virus identification, histopathology, immunohistochemistry and genetic comparison with Scottish mainland isolates

Abstract

During mid-June 1999 peak mortalities of 11% of the total stock per week were seen at a sea cage site of Atlantic salmon, Salmo salar L., post-smolts in the Shetland Isles, Scotland. Virus was isolated on chinook salmon embryo (CHSE) cells in a standard diagnostic test and infectious pancreatic necrosis virus (IPNV) identified by enzyme-linked immunosorbent assay. IPNV was confirmed as serogroup A by a cell immunofluorescent antibody test using the cross-reactive monoclonal antibody AS-1. Four weeks after the main outbreak, virus titres in surviving moribund fish were assayed at >10(10) TCID50 g(-1) kidney. Histopathology of moribund fish was characterized by pancreatic acinar cell necrosis and a marked catarrhal enteritis of the intestinal mucosa. In the liver, necrosis, leucocytic infiltration and a generalized cell vacuolation were noted. IPNV-specific immunostaining was demonstrated in pancreas, liver, heart, gill and kidney tissue. The nucleotide sequence of the coding region of segment A was determined from the Shetland isolate. A 1180 bp fragment of the VP2 gene of this isolate was compared with a 1979 reference isolate from mainland Scottish Atlantic salmon, La/79 and another more recent mainland isolate, 432/00. Both A2 isolates were derived from carrier fish without signs of IPN and serotyped by a plaque neutralization test. The Shetland isolate shows a different nucleotide and amino acid sequence compared with the two isolates from carrier fish. These latter isolates showed identical amino acid sequences in the fragment examined, despite the 21 years separating the isolations. Sequence comparisons with other A2 (Sp) isolates on the database confirm all three Scottish isolates are A2 (Sp).

Infectious pancreatic necrosis virus enters CHSE-214 cells via macropinocytosis

“…This disease has great economic impact in all salmon-farming countries. IPNV produces high mortality in young salmonids 1 , and in later stages of salmon development, the infection becomes persistent and difficult to eradicate 2 .…”

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

“…According to Smail et al (2006), this may be due to denaturing of the viral antigens in the tissues of fish. In the present study, one fish from the 27 samples with positive nested-PCR was negative by immunostaining for the IPNV antigens.…”

Gökkuşağı alabalıklarında (Oncorhynchus mykiss Walbaum, 1792) enfeksiyöz pankreatik nekrozun patogenezisinde apoptozisin rolü

“…Önceki çalışmalarda tanımlanan pankreastaki asiner ve Langerhans adacık hücrelerinin nekrozu ve karakteristik bazofilik intrasitoplazmik inklüzyon cisimcikleri, çalış-manın olgularında da en çok göze çarpan bulgulardandı (9,18,21). Histolojik olarak oldukça karakteristik lezyonlar eşliğinde; dokularda viral antijenin demonstrasyonu ve akuatik Birnavirüs genomunun elektroforez görünümü IPNV'unun varlığını kanıtlamaktadır.…”

“…Salmonid balıklarda mikroskobik olarak lezyonlar öncelikle pankreas ve intestinal mukozada meydana gelir. Pankreasta yaygın asiner ve Langerhans adacık hücrelerinin nekrozu ve intrasitoplazmik inklüzyon cisimcikleri göze çarpar (9,18,21).…”