engleski

Carp Edema Virus: a new threat for the cyprinids inhabiting open waters

Introduction: Carp oedema virus (CEV), the cause of koi sleepy disease, is a DNA virus from the family Poxviridae. The disease was first reported as mass mortalities of koi carps in Japan, but during the last decade, it has been described throughout Europe. The disease is characterized by lethargy, body swelling, ulceration around the mouth and fin basis, gill necrosis and concomitant mortalities rise up to 80%. Due to losses in koi carp and common carp industry, CEV is considered as an emerging disease in European carp aquaculture. The highest losses in Japan where reported to occur in spring and summer with a water temperature of 15 to 35 oC while in the UK the losses were noticed during the winter months, at 6 to 9 oC. In Croatia, the surveillance for the presence of the virus was performed using the samples collected for detection of KHV during the warmer part of the year. A low prevalence of virus, without notification of mortalities or clinical signs, was detected. However, high mortality of carp from the open water occurred during the end of April 2018. Carps weighing 3 to 5 kilograms were mostly affected. The water temperature was up to 25 oC. Samples were submitted to the laboratory for a diagnostic procedure. Methodology: Parasitological, bacteriological and virological examinations were carried out by microscopic analysis, streaking of material from organs onto blood agar and by inoculating the homogenized tissues onto BF2 and EPC cell lines. Nucleic acid extraction and purification from gills and kidney tissues were performed using a commercial kit. Nested PCR was performed using the method described by Matras et al. 2016. Phylogenetic analysis was performed with obtained sequences. Results: Parasitological and bacteriological examinations were negative. All samples tested negative for Koi herpes virus (KHV) using real time PCR. However, samples were positive for CEV. Conclusion: Although there was no proved connection between the introduction of carps for repopulation of open waters from CEV positive carp farms and the mortality event special attention should be employed in such cases. Phylogenetic analysis will elucidate possible pathways of the virus introduction.

CEV, open waters, common carp

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