Abstract
Infectious pancreatic necrosis (IPN), first described as acute viral catarrhal enteritis, is a highly contagious disease with variable pathogenicity that has been linked to genetic variation in the viral VP2 gene encoding the capsid protein. In this study, the IPN virus (IPNV) is isolated from the moribund fish from five of fourteen Iranian trout farms from 2015 to 2017. The affected fish showed mortality rates ranging from 20% to 60%, with the main clinical signs of exophthalmia, darkened skin, and mild abdominal distension, as well as yellow mucoid fluid in the intestine. Histopathological examination of intestinal sections confirmed acute catarrhal enteritis in all samples. RT-PCR assay of the kidney tissue and cell culture (CHSE-214) samples consistently confirmed the presence of the virus. The phylogenetic analysis of the partial VP2 sequence revealed that the detected isolates belong to genogroup 5, and are closely related to the Sp serotype strains of European origin. Characterization of VP2 of all isolates revealed the P217T221 motif that previously was associated with avirulence or low virulence, while all IPNV-positive fish in this study were clinically affected with moderate mortality. The IPNV isolates from Iran are associated with two lineages that appear to have originated from Europe, possibly via imported eggs.
Highlights
Aquaculture, owing to its rapid expansion and interconnected international production operations, creates conditions in which viruses and other pathogens can spread [1].Iran is one of the world-leading producers of freshwater rainbow trout with an annual production above 100k tons, and a respective annual demand for 300–400 million eyed eggs, of which 70% are imported from European countries
From May 2015 to June 2017, the causative agent of five of fourteen outbreaks in Kurdistan, Mazandaran, East Azerbaijan, Kermanshah, and Hamedan provinces in Iran were diagnosed as Infectious pancreatic necrosis virus (IPNV)
The other nine outbreaks were caused by the prevalent rhabdoviruses: Three infectious hematopoietic necrosis virus (IHNV), and six viral hemorrhagic septicemia virus (VHSV) cases [4,5]
Summary
Aquaculture, owing to its rapid expansion and interconnected international production operations (including extensive trade of eyed eggs and animals at different life stages), creates conditions in which viruses and other pathogens can spread [1]. Iran is one of the world-leading producers of freshwater rainbow trout with an annual production above 100k tons, and a respective annual demand for 300–400 million eyed eggs, of which 70% are imported from European countries. The industry faced significant losses, due to viral diseases, such as rhabdoviruses and IPNV, which was first reported in the late 2000s, and since has become endemic [2,3,4,5].
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