Persistence of cyprinid herpesvirus 2 in asymptomatic goldfish Carassius auratus (L.) that survived an experimental infection

Cyprinid herpesvirus 2 (CyHV‐2) is the causative agent of herpesviral haematopoietic necrosis (HVHN) in goldfish, Carassius auratus, and Prussian carp, C. auratus gibelio. In this study, we investigated virus persistence in goldfish experimentally infected with CyHV‐2. Virus DNA presence in organs was monitored in survivors reared at a virus permissive temperature and also in survivors treated with a non‐permissive temperature for 4 days, initiated at three different time points post‐infection in order to obtain fish with different virus loads. We detected virus DNA in all organs tested at 51 days post‐infection (dpi) and in the spleen, trunk kidney and gills of survivors at 81 dpi, although the virus load in fish influenced the subsequent number of organs that tested positive for virus DNA. In addition, some organs dissected from four out of five asymptomatic survivors tested positive by PCR following incubation in vitro in a medium for 5 days. Following inoculation with the homogenate of PCR‐positive kidney incubated in vitro, one of the three inoculated fish died, showing that the detected virus by PCR produced infectious particles. This study suggests that CyHV‐2 can establish a persistent infection in some organs, especially the spleen and trunk kidney, and that asymptomatic surviving fish can be a source of infection.     

Establishment, characterization and viral susceptibility of a new cell line derived from goldfish, Carassius auratus (L.), tail fin

A continuous cell line [goldfish tail fin (GFTF)] derived from a goldfish tail fin, Carassius auratus, was established and characterized. GFTF cells predominantly consist of fibroblast-like cells that were maintained and subcultured more than 50 times over a period of 15 months. Cells grew at temperatures between 15 and 37°C, with an optimum temperature of 25°C. The growth rate of GFTF cells increased proportionally with the foetal bovine serum (FBS) concentration (5-20%), with optimum growth at 20% FBS. The chromosome numbers were 88-112, with a modal peak of 104 chromosomes. Five known fish viruses were tested to determine susceptibility. Results demonstrated that GFTF is susceptible to snakehead rhabdovirus, spring viraemia of carp virus and channel catfish virus (CCV). In addition, GFTF demonstrated a higher sensitivity to, and increased viral production of, CCV than that observed in the control cell line, channel catfish ovary cells. This suggests that GFTF cells would be useful as a diagnostic tool for viral diseases in this fish species, as well as for the isolation and study of goldfish viruses in the future. Furthermore, these cells were transfected with pEGFP-N1 vector DNA and some fluorescent signals were observed, suggesting that GFTF cells could be a useful tool for transgenic and genetic manipulation studies.     

Distribution of the introduced cyprinid herpesvirus 3 in a wild population of common carp, Cyprinus carpio L.

Cyprinid herpesvirus 3 (CyHV-3), which causes a lethal disease in common carp, Cyprinus carpio L., and koi, C. carpio koi , first occurred in Lake Biwa, Japan in 2004. To elucidate distribution of CyHV-3 in a wild common carp population, we conducted a PCR survey of CyHV-3 among such fish in Lake Biwa in 2006. Only 6% (1/18) of the common carp smaller than 300 mm were positive with PCR, whereas 31% (18/58) of fish larger than 300 mm were positive. To evaluate their past exposure to CyHV-3 infection based on the presence of antibodies, we also measured the levels of serum anti-CyHV-3 antibodies in the carp, using an enzyme-linked immunosorbent assay. None (0/26) of the fish smaller than 300 mm was positive for the antibodies, whereas 54% (33/61) of fish larger than 300 mm were positive. Of the antibody-positive individuals, 44% (14/32) were also positive by PCR strongly suggesting that wild common carp that survived infection become CyHV-3 carriers. Five individuals were positive by PCR but negative for antibodies indicating that their infection with CyHV-3 had occurred recently. These results suggest that transmission of CyHV-3 from carriers to naïve common carp is still occurring in Lake Biwa.     

The life cycle of Chloromyxum auratum (Myxozoa) from goldfish, Carassius auratus (L.), involves an antonactinomyxon actinospore

The myxozoan parasite Chloromyxum auratum Hallett, Atkinson, Holt, Banner & Bartholomew, 2006 , was shown experimentally to have a two‐host life cycle which involved a previously undescribed antonactinomyxon actinospore stage. Myxospores obtained from gall bladders of naturally infected feral goldfish, Carassius auratus (L.), were used to infect samples of mixed species of oligochaete worms obtained from the same locality as the fish: Fern Ridge Dam, Oregon, USA. After some 110 days post‐exposure, actinospores were detected from the water above the oligochaetes. The 18S rDNA sequence of these actinospores was identical to the original myxospores. Spore release was sporadic, of low intensity and short duration, which confounded efforts to identify the host oligochaete species and infect naïve fish. This is the first life cycle that incorporates an actinospore of the collective group Antonactinomyxon, and the first life cycle demonstrated in the laboratory for a species of Chloromyxum.     

Status of the crucian carp, Carassius carassius (L.), in the UK

The crucian carp, Carassius carassius (L.), is a small fish of restricted distribution in the UK, which is probably only native to central and eastern England. The crucian carp is endemic to northern Europe. It has been widely confused with the introduced and congeneric goldfish, Carassius auratus (L.), and forms hybrids with that species and the introduced Cyprinus carpio L. The status of this fish has become confused with the presence of the congener and its hybrids, and it is now thought to be less frequent in occurrence than formerly.     

抗鲤疱疹Ⅱ型病毒卵黄抗体制备及其功能鉴定

为制备抗鲤疱疹Ⅱ型病毒(CyHV-2)的卵黄抗体,探索防治异育银鲫(Carassius auratus gibelio)鳃出血病的新方法和途径,本研究利用原核表达系统产生具免疫原性的重组CyHV-2-ORF72衣壳蛋白,纯化后免疫蛋鸡;二次免疫后采用间接ELISA法抽检免疫蛋的特异性卵黄抗体(IgY)含量,收集抗体效价...     

Hematological response in fish: pronephric and splenic involvements in the goldfish,Carassius auratus L.

Pronephric and splenic involvements in erythropoiesis and in stress-induced hematological response by goldfish,Carassius auratus, were examined under conditions of minimal stress and following transient (3h) temperature-induced elevation of O₂ demand and transient (3h) exposure to hypoxia. Although hemoglobin content and red cell numbers were little affected, the ontogenic composition of the circulating erythrocyte population was significantly altered by both types of respiratory challenge and also by the stresses associated with capture, air exposure during transfer and intraperitoneal administration of label. Juvenile cell numbers increased sharply while mature erythrocyte abundances declined. Consistent with this, [³H] methylthymidine-labeled cell numbers rose in both spleen and pronephros following imposition of stress. Splenic erythropoietic activity was modest relative to that of the pronephros. Our observations point to a readily triggered response involving: [1] release of cells reservoired in the spleen and pronephros, [2] increased erythropoiesis and [3] karyorrhexis. We suggest that while the magnitude of response may depend on the quality and magnitude of the imposed stress, its central features are essentially constant.     

Intracellular mechanisms mediating gonadotropin and growth hormone release in the goldfish,Carassius auratus

Evidence for the involvement of Ca²⁺, protein kinase C, cAMP, and arachidonic acid metabolism in mediating gonadotropin (GTH) and growth hormone (GH) release in the goldfish is reviewed. Models for the signal transduction pathways mediating GTH-releasing hormone (GnRH) and dopamine actions on GTH and GH secretion are postulated. A novel hypothesis that two GnRHs which bind to the same receptor type activate different transduction cascade in two different cell types (GTH vs. GH) as well as within the same cell type (GTH) is presented.

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Résumé Cette revue présente les données expérimentales démontrant l'implication de Ca⁺⁺, de la protéine kinase C et du métabolismes de l'acide arachidonique dans les mécanismes régulant la sécrétion des hormones gonadotrope (GTH) et de croissance (GH). Des modèles de signaux de transduction de l'action de la gonadolibérine (GnRH) et de la dopamine sur la sécrétion de GTH et de GH sont proposés. Les deux GnRHs existant chez le poisson rouge pourraient se lier au même type de récepteur et activer différentes voies de transduction dans deux différents types cellulaires (GTH vs. GH) ou dans un seul type (GTH).

     

A comparison of artificial and natural foods and their combinations in the rearing of goldfish, Carassius auratus (L.)

Intensive grow‐out of goldfish, Carassius auratus (L.), larvae and juveniles in closed systems requires the control of environmental conditions and feeding. This study investigates the use of different types of live food and combinations of live food and dry food in a series of four rearing experiments. Juvenile goldfish can be weaned from Artemia onto live food at about 24 days after the onset of feeding without causing a reduction in growth and survival. The replacement of Artemia by Daphnia at day 10 appears feasible, as growth and survival were not significantly affected. Fish fed decapsulated Artemia cysts grew better than fish fed live Artemia. Within the first 14 days, goldfish juveniles should be fed at least 155 cysts per fish per day to achieve fast growth and to minimize size variation.     

Susceptibility of isogeneic ginbuna Carassius auratus langsdorfii Temminck et Schlegel to cyprinid herpesvirus‐2 (CyHV‐2) as a model species

Herpesviral haematopoietic necrosis (HVHN), caused by cyprinid herpesvirus‐2 (CyHV‐2), has affected the commercial production of the goldfish Carassius auratus and gibelio carp Carassius auratus gibelio. High water temperature treatments are reported to reduce the mortality rate of infected goldfish and elicit immunity in the survivors. To define the mechanism by which this intervention induces resistance, clonal ginbuna Carassius auratus langsdorfii, which is closely related to both species and has been used in fish immunology, may represent a promising model species. In this study, we investigated the susceptibility of clonal ginbuna strains to CyHV‐2 and the effect of high water temperature treatment on infected ginbuna and goldfish. Experimental intraperitoneal infection with CyHV‐2 at 25 °C caused 100% mortality in ginbuna strains, which was accompanied by histopathological changes typical of HVHN. Both infected ginbuna S3n strain and goldfish, exposed to high temperature for 6 days [shifting from 25 °C (permissive) to 34 °C (non‐permissive)], showed reduced mortalities after the 1st inoculation, and subsequent 2nd virus challenge to 0%, indicating induction of immunity. It was concluded that ginbuna showed a similar susceptibility and disease development in CyHV‐2 infection compared to goldfish, suggesting that ginbuna can be a useful fish model for the study of CyHV‐2 infection and immunity.     

First detection of Cyprinid Herpesvirus 2 (CyHV‐2) in goldfish (Carassius auratus) in France

Massive mortalities of Carassius auratus (L.) occurred in a farm in France during summer 2014. Fish presented anorexia, loss of scales and large amounts of mucus on the gills. Necrosis of the distal tip of the filament and the lamellae, combined with fusion of the lamellae, was observed, as well as necrosis in the hematopoietic organs and in the digestive tract. The histological examination led to hypothesize the implication of a virus in the mortality. The presence of cyprinid herpesvirus 2 (CyHV‐2) in dead fish was demonstrated by amplification and sequencing of portions of the DNA polymerase and helicase genes, both sequences exhibiting 100% identity with CyHV‐2 from Japan. In an attempt to find genetic markers of variation, two regions containing tandem repeats in the Japanese genome were amplified from a virus‐positive sample from the present outbreak. A first region (mB) was fully identical to the Japanese isolate. However, the second region (mA) exhibited a range of deletions and substitutions compared to CyHV‐2 from Japan. This is the first report of CyHV‐2 in France in association with mortality of goldfish and the first identification of a molecular marker for its tracing.