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1.
Sixteen specimens of female crucian carp, Carassius carassius (L.), during the breeding season, were investigated for post‐mortem and full diagnostic examination during a mortality outbreak in a tributary stream of the Arno River in Tuscany in 2011. Necropsy highlighted the presence of a swollen anus and widespread haemorrhages in the body, fins, gills and eyes. Haemorrhages in internal organs and spleen granulomas were also observed. Bacteria isolated from the brain, kidney and spleen of affected fish were identified as A. sobria. Microscopic lesions observed in gills were characterized by necrosis of the secondary lamellae, congestion and multifocal lamellar fusion. The kidney showed necrosis, oedema, fibrin exudation and areas of haemorrhages, while in the spleen the main lesions were by multifocal necrosis of the lymphoid tissue. In the gills, transmission electron microscopy revealed herpesvirus‐like particles, subsequently identified as Cyprinid herpesvirus‐2 (CyHV‐2) with a nested PCR protocol. Although it was not possible to attribute a pathogenic role to CyHV‐2 in this mortality event, the identification of this herpesvirus in crucian carp increases the concern about its potential role in this species.  相似文献   

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3.
Zebrafish has become a popular research model in the last years, and several diseases affecting zebrafish research facilities have been reported. However, only one case of naturally occurring viral infections was described for this species. In 2015, infectious spleen and kidney necrosis virus (ISKNV) was detected in zebrafish from a research facility in Spain. Affected fish showed lethargy, loss of appetite, abnormal swimming, distention of the coelomic cavity and, in the most severe cases, respiratory distress, pale gills and petechial haemorrhages at the base of fins. Cytomegaly was the most relevant histopathological finding in organs and tissues, sometimes associated to degenerative and necrotic changes. ISKNV belongs to the relatively newly defined genus Megalocytivirus, family Iridoviridae, comprising large, icosahedral cytoplasmic DNA viruses. This is the first case of naturally occurring Megalocytivirus infection in zebrafish research facilities, associated with morbidity. The virus has been identified based on both pathologic and genetic evidence, to better understand the pathogenesis of the infection in zebrafish and the phylogenetic relationship with other iridoviruses. Given the ability of megalocytiviruses to cross‐species boundaries, it seems necessary to implement stringent biosecurity practices as these infections may invalidate experimental data and have major impact on laboratory and cultured fish.  相似文献   

4.
Pollution by the heavy metal lead (Pb) has become a threat to both aquaculture and food safety. In this study, the protective effects of a selected probiotic with good Pb binding capacity (Lactobacillus plantarumCCFM8661) against waterborne Pb exposure were evaluated in Nile tilapia (Oreochromis niloticus). One hundred and eighty fish were divided into four groups as control, Pb‐only, Pb‐plus‐CCFM8661 and CCFM8661‐only. Fish were exposed to a dose of waterborne Pb level at 1 mg L?1 for 4 weeks, and the probiotic was administered at 108 CFU g?1 in fish diet twice daily. The results showed that dietary supplementation of CCFM8661 ameliorated the growth performance and prevented the death of Pb‐exposed fish. Cotreatment with Pb and CCFM8661 also effectively decreased Pb accumulation in kidney, liver, gonad, brain, gills and muscle. Moreover, the administration of this probiotic alleviated Pb‐induced oxidative stress, recovered digestive enzyme activities and blood δ‐aminolevulinic acid dehydratase activity, reversed alterations in innate immune status and decreased the frequencies of the nuclear abnormalities in peripheral blood erythrocytes of fish. These results suggested that CCFM8661 may be a novel dietary supplement against Pb toxicity at least in tilapia.  相似文献   

5.
Viral haemorrhagic septicaemia virus, Genogroup IVa (VHSV), was highly infectious to Pacific herring, Clupea pallasii (Valenciennes), even at exposure doses occurring below the threshold of sensitivity for a standard viral plaque assay; however, further progression of the disease to a population‐level epizootic required viral amplification and effective fish‐to‐fish transmission. Among groups of herring injected with VHSV, the prevalence of infection was dose‐dependent, ranging from 100%, 75% and 38% after exposure to 19, 0.7 and 0.07 plaque‐forming units (PFU)/fish, respectively. Among Pacific herring exposed to waterborne VHSV (140 PFU mL?1), the prevalence of infection, geometric mean viral tissue titre and cumulative mortality were greater among cohabitated herring than among cohorts that were held in individual aquaria, where fish‐to‐fish transmission was prevented. Fish‐to‐fish transmission among cohabitated herring probably occurred via exposure to shed virus which peaked at 680 PFU mL?1; shed virus was not detected in the tank water from any isolated individuals. The results provide insights into mechanisms that initiate epizootic cascades in populations of wild herring and have implications for the design of VHSV surveys in wild fish populations.  相似文献   

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7.
Enteric septicaemia of catfish (ESC) caused by Edwardsiella ictaluri is becoming an increasing problem in aquaculture and has been reported worldwide in a variety of fish species. This study reports ESC in hybrid catfish, Clarias macrocephalus (Günther) × Clarias gariepinus (Burchell), cultured in southern Thailand. The bacteria were identified as E. ictaluri by conventional and rapid identification systems, as well as by genetic and phylogenetic characterization. Analysis of 16S rRNA indicated 100% homology to the 16S rRNA sequence of several E. ictaluri strains in GenBank. Plasmid profiles demonstrated 4.0‐ and 5.6‐kb plasmids, compared with the 4.8‐ and 5.6‐kb plasmids in the US isolates, and representative genes of three of the four known pathogenicity islands of US isolates were present. Serologically, lipopolysaccharide (LPS) purified from the Thai isolates was not recognized by a monoclonal antibody against the LPS of US isolates. Fish experimentally infected with E. ictaluri showed 23–100% mortality within 14 days with a 168‐h LD50 of 6.92 × 107 CFU mL?1 by immersion and a 96‐h LD50 of 1.58 × 106 CFU fish?1 by intraperitoneal injection. Examination of tissue sections obtained from both naturally and experimentally infected fish indicated that infection of hybrid catfish with E. ictaluri produced lesions in several organs including liver, kidney, spleen, heart and brain. Histopathology findings included cellular necrosis, focal haemorrhage, infiltration of lymphocytes and multifocal granulomatous inflammation in the infected organs.  相似文献   

8.
Asian seabass (Lates calcarifer) has been designated as a candidate species for open sea cage culture in India. A case of vibriosis in Asian seabass reared in open sea floating cages is reported. Haemorrhage and ulcer were observed grossly in the diseased fish. The pathogen, identified as Vibrio alginolyticus based on biochemical and molecular characterization, was isolated from liver, gill, kidney, brain and blood. Histological examination of the diseased fish showed congestion, haemorrhage and necrosis in vital organs. The LD50 studies showed that the organism was virulent to Asian seabass, and the LD50 value was 103.2 CFU g?1 fish.  相似文献   

9.
Fish rhabdoviruses are a family of viruses responsible for large‐scale fish die‐offs worldwide. Here, we reported the isolation and identification of a member of rhabdoviruses from wild largemouth bass (Micropterus salmoides) in the coastal area of the Pearl River Estuary, China. This virus isolate was identified as viral haemorrhagic septicaemia virus (VHSV) by specific RT‐PCR. Furthermore, the virus (VHSVLB2018) was isolated by cell culture using fathead minnow cells and confirmed by RT‐PCR. Electron microscopy showed the presence of bullet‐shaped viral particles in the cytoplasm of infected cells. The complete sequencing of VHSVLB2018 confirmed that it was genome configuration typical of rhabdoviruses. Phylogenetic analysis based on whole‐genome sequences and G gene nucleotides sequences revealed that VHSVLB2018 was assigned to VHSV genogroup Ⅳa. The pathogenicity of VHSVLB2018 was determined in infection experiments using specific pathogen‐free largemouth bass juveniles. VHSVLB2018‐infected fish showed typical clinical signs of VHSV disease, including darkened skin, petechial haemorrhages and pale enlarged livers, with the cumulative mortalities reached 63.3%–93.3% by 7 days post‐infection. VHSVLB2018 was re‐isolated from dead fish and confirmed by RT‐PCR. Together, this is the first report of isolation and identification of a VHSV isolate from wild largemouth bass in China.  相似文献   

10.
Contamination of aquatic ecosystems by metals causes various biochemical changes in aquatic organisms, and fish are recognized as indicators of environmental quality. Silver catfish were exposed to six concentrations of zinc (Zn): 1.0, 2.5, 5.0, 7.5, 10.0 and 12.5 mg/L for 96 h to determine the mean lethal concentration (LC50). The value obtained was 8.07 mg/L. In a second experiment, fish were exposed to concentrations of 1.0 or 5.0 mg/L Zn and a control for 96 h. Afterward, the tissues were collected for biochemical analysis. Lipid peroxidation, as indicated by thiobarbituric acid-reactive substance (TBARS), decreased in the liver and brain for all Zn concentrations tested, while in the gills TBARS levels increased at 1.0 mg/L and declined at 5.0 mg/L. Zn increased protein carbonyls in the muscle of silver catfish and decreased it in the other tissues. The enzyme superoxide dismutase increased in both exposed groups. However, catalase did not change. Glutathione S-transferase decreased in the liver and increased in the gills (1.0 mg/L), muscle (5.0 mg/L) and brain (1.0 and 5.0 mg/L). Nonprotein thiols changed only in brain and muscle tissue. Zn exposure inhibited acetylcholinesterase (AChE) activity in the brain at both concentrations tested, but did not change it in muscle. Exposure to Zn inhibited the activity of Na+/K+-ATPase in the gills and intestine at both concentrations tested. Our results demonstrate that Zn alters biochemical parameters in silver catfish and that some parameters such as AChE and Na+/K+-ATPase could be considered as early biomarkers of waterborne Zn toxicity.  相似文献   

11.
Experiments were designed to determine the effects of temperature and salinity on the virulence of Edwardsiella tarda to Japanese flounder, Paralichthys olivaceus. In the temperature experiment, a two‐factor design was conducted to evaluate the effects of both pathogen incubation temperature and fish cultivation temperature on pathogen virulence. E. tarda was incubated at 15, 20, 25 and 30±1°C, and the fish (mean weight: 10 g) were reared at 15, 20 and 25±1°C respectively. The fish reared at different temperatures were infected with the E. tarda incubated at different temperatures. The results of a 4‐day LD50 test showed that temperature significantly affected the virulence of E. tarda (P<0.01) and the interaction between the two factors was also significant (P<0.01). For fish reared at 15°C the virulence of E. tarda was the highest at 25°C of pathogen incubation, followed by 20, 15 and 30°C. When the fish rearing temperature was raised to 20 and 25°C, the virulence of E. tarda incubated at all temperatures increased. Isolation testing demonstrated results similar to those of LD50. The higher rearing temperature increased the proliferation rate of the pathogen in fish. In the salinity experiment, the incubation salinity of E. tarda was at 0, 10, 20 and 30 g L?1, respectively, and the fish with mean weight of 50 g were cultured in natural seawater of 30 g L?1. The results of one‐way anova in 4‐day LD50 test showed that incubation salinity significantly affected virulence. Virulence was lower when the salinity of the incubation medium was at 0 and 30 g L?1, higher at 10 and 20 g L?1. The results of isolation test were in accordance with those of LD50. At 20 g L?1E. tarda had a faster proliferation rate than that at 10 g L?1.  相似文献   

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13.
A complement‐dependent 50% plaque neutralization test was used to assess the neutralizing antibody response in sera of muskellunge, Esox masquinongy, experimentally infected with viral haemorrhagic septicaemia virus (VHSV, genotype IVb) by immersion. Groups of muskellunge were challenged with varying concentrations of VHSV: Group 1 with 102 plaque‐forming units (pfu) mL?1, Group 2 with 4 × 103 pfu mL?1, Group 3 with 105 pfu mL?1 and Group 4 with 0 pfu mL?1. The fish were held at a temperature of 11 ± 1 °C and were sampled over a 20‐week period. Neutralizing antibodies were not detected in sera of any of the negative control fish throughout the study. Low neutralizing titres were detected in Groups 1–3 by 6 days post‐infection (p.i.). Neutralizing titres of <80 were not detected again until 3, 4 and 7 weeks p.i. for Groups 2, 3 and 1, respectively, with peak titres for those groups occurring 16, 11 and 17 weeks p.i., respectively. VHSV was detected in serum for up to 11 weeks p.i. Results of this study show that survivors can be detected by a serological technique, despite being virus negative. This may benefit the investigation of VHSV IVb distribution in the Great Lakes and the study of host immune responses to this emerging sublineage.  相似文献   

14.
Carp liver, gills, intestine, kidneys, heart and spleen were studied by histology after the fish were exposed to microcystins by gavage, immersion and intraperitoneal administration. Intraperitoneal inoculation with microcystins caused necrosis or dose- dependent degeneration in the liver, gills and kidneys. Gavaging with microcystins caused changes in the histopathology of the liver and gills. Cellular degeneration and necrosis occurred in the liver, gills and kidneys when carp were introduced to a tank containing 1.7 μg ml?1 of microcystins. Lesions were not observed in the heart, spleen or intestines from any of the treated carp. Microcystins administered by intraperitoneal injection at a concentration of 50 μg kg?1 were lethal to all fish within 8 h, while gavaging with 250 μg kg?1 of microcystins caused minimal damage in the tissues studied.  相似文献   

15.
A candidate vaccine against Aeromonas hydrophila in rainbow trout, Oncorhynchus mykiss, was developed using a bacterial lysate. To test the strength of protection, A. hydrophila challenge models were compared using injection into both the intraperitoneal (IP) cavity and the dorsal sinus (DS) with selected doses of live bacteria washed in saline or left untreated. Unlike the IP route, injection into the DS with either saline washed or unwashed cells resulted in consistent cumulative mortality and a dose response that could be used to establish a standard challenge having an LD50 of approximately 3 × 107 colony forming units per fish. Survivors of the challenge suffered significantly lower mortality upon re‐challenge than naïve fish, suggesting a high level of acquired resistance was elicited by infection. Passive immunization using serum from hyper‐immunized fish also resulted in significantly reduced mortality indicating protection can be transferred and that some portion of resistance may be antibody mediated. Vaccination of groups of rainbow trout with A. hydrophila lysate resulted in significant protection against a high challenge dose but only when injected along with Freund’s complete adjuvant. At a low challenge dose, mortality in all groups was low, but the bacterial lysate alone appeared to offer some protection.  相似文献   

16.
分别以1.30 mg/kg、1.69 mg/kg、2.19 mg/kg、2.86 mg/kg、3.71 mg/kg、4.83 mg/kg、6.27 mg/kg、8.16 mg/kg剂量的伊维菌素(ivermectin)对松浦镜鲤(Cyprinus specularis songpu)进行口灌,并设置空白对照和溶剂对照,给药后连续观察96 h,记录各组鱼的行为和死亡情况。用SPPS软件计算得出松浦镜鲤口灌伊维菌素的96 h LD50为4.04 mg/kg,95%可信区间为3.42~4.80 mg/kg。对给药组和对照组鱼进行血细胞分析,发现随着给药剂量的增加,红细胞数无明显变化,血红蛋白浓度呈上升趋势,而白细胞数呈下降趋势。通过组织切片观察,发现伊维菌素给药剂量为4.83 mg/kg时松浦镜鲤体内组织开始出现明显的病理变化。大剂量口灌伊维菌素后,松浦镜鲤肠绒毛出现坏死、脱落现象,肝细胞萎缩、肝血窦变大,肾小管上皮细胞变性、坏死,心肌纤维萎缩、变性。本研究通过探讨伊维菌素对松浦镜鲤的毒性效应,旨在为松浦镜鲤养殖过程中科学合理的使用伊维菌素提供基础数据和科学依据。  相似文献   

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18.
Procedures for a viral replication in excised fin tissue (VREFT) assay were adapted to Pacific herring, Clupea pallasii, and optimized both to reduce processing time and to provide the greatest resolution between naïve herring and those previously exposed to viral haemorrhagic septicaemia virus (VHSV), Genogroup IVa. The optimized procedures included removal of the left pectoral fin from a euthanized fish, inoculation of the fin with >105 plaque‐forming units (PFU) mL?1 VHSV for 1 h, rinsing the fin in fresh medium six times to remove unadsorbed virions, incubation of the fin in fresh medium for 4 days and enumeration of the viral titre in a sample of the incubation medium by plaque assay. The optimized VREFT assay was effective at identifying the prior exposure history of laboratory‐reared Pacific herring to VHSV. The geometric mean VREFT value was significantly greater (P < 0.01) among naïve herring (1.2 × 103 PFU mL?1) than among groups that survived exposure to VHSV (1.0–2.9 × 102 PFU mL?1); additionally, the proportion of cultures with no detectable virus was significantly greater (P = 0.0002) among fish that survived exposure to VHSV (39–47%) than among naïve fish (3.3%). The optimized VREFT assay demonstrates promise for identifying VHSV exposure history and forecasting disease potential in populations of wild Pacific herring.  相似文献   

19.
Pathological manifestations in rainbow trout (Oncorhynchus mykiss) following experimental waterborne infection with Yersinia ruckeri serotype O1 biotype 2 (strain 07111224) were investigated. Rainbow trout were exposed to 8 × 107 CFU/ml of Y. ruckeri by bath for 6 hr, and mortality was then monitored for 22 days post‐infection (dpi). Organs were sampled at 3 dpi and also from moribund fish showing signs of severe systemic infection such as bleeding, exophthalmia or erratic swimming behaviour. Y. ruckeri was observed in the meninges and diencephalon of the brain, and lamina propria of olfactory organ at 3 dpi. At 12 dpi, Y. ruckeri had spread throughout the brain including cranial connective tissues and ventricles and the infection was associated with haemorrhages and an infiltration with leucocytes. Y. ruckeri infection and associated with leucocyte infiltration were observed at 13 dpi. In conclusion, Y. ruckeri strain 07111224 causes encephalitis in the acute phase of infection, which could explain why Y. ruckeri‐affected fish show exophthalmia and erratic swimming known as signs of ERM.  相似文献   

20.
Lumpfish (Cyclopterus lumpus), a native fish of the North Atlantic Ocean, is utilized as cleaner fish to biocontrol sea lice infestations in Atlantic salmon aquaculture. However, bacterial infections are affecting cleaner fish performance. Vibrio anguillarum, the aetiological agent of vibriosis, is one of the most frequent bacterial infections in lumpfish, and effective vaccine programmes against this pathogen have been identified as a high priority for lumpfish. Vibrogen‐2 is a commercial polyvalent bath vaccine that contains formalin‐inactivated cultures of V. anguillarum serotypes O1 and O2, and Vibrio ordalii. In this study, we evaluated Vibrogen‐2 efficacy in lumpfish against a local isolated V. anguillarum strain. Two groups of 125 lumpfish were bath‐immunized, bath‐boost‐immunized at four weeks post‐primary immunization, and intraperitoneally (i.p.) boost‐immunized at eight weeks post‐primary immunization. The control groups were i.p. mock‐immunized with PBS. Twenty‐seven weeks post‐primary immunization, the fish were i.p. challenged with 10 or 100 times the V. anguillarum J360 LD50 dose. After the challenge, survival was monitored daily, and samples of tissues were collected at ten days post‐challenge. Commercial vaccine Vibrogen‐2 reduced V. anguillarum tissue colonization and delayed mortality but did not confer immune protection to C. lumpus against the V. anguillarum i.p. challenge.  相似文献   

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