ABSTRACT:The first outbreaks of a disease connected with high mortality of common carp and koi carp caused by koi herpesvirus (KHV) were reported in 1998 in Israel and in the United States. Since then, several cases have been confirmed all over the world. At present, this viral disease is considered to be one of the most risky factors affecting populations of common carp and koi carp. Affected fish become disoriented and swim erratically with high breathing frequency, swollen gills and partially local skin lesions. The virus was isolated from the tissues of fish showing signs of the disease and subsequently cultured on koi fin (KF-1) cells. Electron microscopic examinations revealed morphological signs identical with viruses of the family Herpesviridae. Analysis of virion polypeptides and gene DNA showed the differences between KHV and the well-known herpesvirus of cyprinids, Herpesvirus cyprini (CHV), and Channel catfish virus (CCV). Water temperature is a factor influencing the onset and severity of disease. Fish seem most susceptible at water temperatures of 18-28°C, no morbidities occur at 13°C and 30°C. At present, diagnosis of KHV is mainly based on detection of viral DNA by PCR method.

No abstract

From 22 May to 10 June 2011 massive mortality of Prussian carp Carassius gibelio was observed in alluvial Lake Ř ehačka close to the Elbe River in the Czech Republic. More than 1400 kg of dead fish were collected and no other fish species were affected. Further molecular and cytogenetic investigation of fish (n = 232) revealed that the Ř ehačka population of Prussian carp consisted exclusively of gynogenetic triploid females. The causative agent was identified by means of molecular and electron microscopy as a herpesviral hematopoietic necrosis virus (Cyprinid herpes virus 2, CyHV-2). This is the first report of CyHV-2 from the Czech Republic and the second finding worldwide of CyHV-2 causing mass mortality of C. gi be lio. Some other localities in the upper Elbe River basin where C. gibelio was affected are also noted. We assume that the massive wave of deaths of all female gynogenetic Prussian carp can be attributed to limited genetic variation and the favourable conditions for development of viral disease. KEY WORDS: Cypriniformes · Herpesvirus · Triploid · Gynogenetic · MortalityResale or republication not permitted without written consent of the publisher

Cyprinids are the most highly produced group of fishes globally, with common carp being one of the most valuable species of the group. Koi herpesvirus (KHV) infections can result in high levels of mortality, causing major economic losses, and is listed as a notifiable disease by the World Organization for Animal Health. Selective breeding for host resistance has the potential to reduce morbidity and losses due to KHV. Therefore, improving knowledge about host resistance and methods of incorporating genomic data into breeding for resistance may contribute to a decrease in economic losses in carp farming. In the current study, a population of 1,425 carp juveniles, originating from a factorial cross between 40 sires and 20 dams was challenged with KHV. Mortalities and survivors were recorded and sampled for genotyping by sequencing using Restriction Site-Associated DNA sequencing (RADseq). Genome-wide association analyses were performed to investigate the genetic architecture of resistance to KHV. A genome-wide significant QTL affecting resistance to KHV was identified on linkage group 44, explaining approximately 7% of the additive genetic variance. Pooled whole genome resequencing of a subset of resistant (n = 60) and susceptible animals (n = 60) was performed to characterize QTL regions, including identification of putative candidate genes and functional annotation of associated polymorphisms. The TRIM25 gene was identified as a promising positional and functional candidate within the QTL region of LG 44, and a putative premature stop mutation in this gene was discovered.

No abstract