Isolation and confirmation of viral nervous necrosis (VNN) disease in golden grey mullet (Liza aurata) and leaping mullet (Liza saliens) in the Iranian waters of the Caspian Sea.
The present study was conducted on 428 moribund mullet fish samples to isolate and identify the causative agent of a mysterious acute mortality which recently occurred in wild mullets in Iranian waters of Caspian Sea, suspected to be due to viral nervous necrosis (VNN) disease. Disease investigation was carried out employing various diagnostic procedures such as virology, bacteriology, parasitology, haematology, histopathology, IFAT, IHC and nested RT-PCR. Brain and eye samples of affected fishes were collected in sterile conditions and then kept at -80°C for cell culture isolation and nested RT-PCR detection of the causative agent. Other tissue samples were also collected and fixed for histopathology, IHC and EM examinations. CPE was observed in cell cultures at 6days after inoculation. Nine samples were found positive with virological assay. Nested RT-PCR, performed on suspected tissues and CPE positive samples, showed that about 21 tissue samples and all the CPE positive samples were positive for VNN virus (VNNV). IFAT was selected as a confirmatory method for detecting the presence of Betanodavirus antigen, cell culture isolation results and nested RT-PCR findings. Moreover, VNNV particles with 25-30nm in diameter were also visualized in the infected brain and retina. In pathogenicity studies, guppy fishes bathed in VNNV-infected tissue culture (10(-4) TCID50) showed clinical signs similar to naturally infected mullet after 15days post infection (dpi), with mortality rates reaching up to 100% at 30dpi. Affected organ samples as examined by cell culture isolation, IFAT, IHC and histopathology, revealed the presence of VNNV in the guppy fishes. In conclusion, it was confirmed that VNNV was the main causative agent for the disease outbreak in mullet fish in the Caspian Sea, and this is such first official report of VNN disease from Iran.
Aquatic Animal Health & Diseases Dept., Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Islamic Republic of Iran. Electronic address: zorrieh@yahoo.com.
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MEJ
Zorriehzahra
Department of Fish Diseases, Inland Water Aquaculture Institute, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Anzali, Gilan, Islamic Republic of Iran.
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Ghasemi
Department of Fish Diseases, Caspian Sea Ecology Research Center, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Sari, Islamic Republic of Iran.
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M
Ghiasi
Department of Fisheries, Bandar-e-Anzali Branch, Islamic Azad University, Gilan, Islamic Republic of Iran.
S Haghighi
SH
Karsidani
OIE Reference Lab. for Encephalopathy and Retinopathy, Instituto Zooprofilattico Sperimentale delle Venezie,Viale dell'Università, Padova, Italy.
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Bovo
Department of Aquaculture, Falavarjan Branch, Islamic Azad University, Falavarjan, Islamic Republic of Iran.
A
A
Nazari
Aquatic Animal Health & Diseases Dept., Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Islamic Republic of Iran.
M
M
Adel
Department of Stebicef, Università degli Studi di Palermo, Via Archirafi, Palermo, Italy.
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V
Arizza
Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India.
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Dhama
D000818:Animals; D002460:Cell Line; D005393:Fish Diseases / Q000401:mortality / Q000473:pathology / Q000821:virology*; D019084:Fluorescent Antibody Technique, Indirect; D007150:Immunohistochemistry; D007492:Iran; D046529:Microscopy, Electron, Transmission; D030381:Nodaviridae / Q000302:isolation & purification* / Q000472:pathogenicity / Q000648:ultrastructure; D009792:Oceans and Seas; D016133:Polymerase Chain Reaction; D012327:RNA Virus Infections / Q000401:mortality / Q000473:pathology / Q000821:virology*; D023701:Smegmamorpha; D016019:Survival Analysis
Caspian sea; Golden grey mullet (Liza aurata); Iran; Leaping mullet (Liza saliens); Viral nervous necrosis