全国水产养殖病害防治网络快讯

全国水产养殖病害防治网络快讯主办单位：中国水产学会科普工作委员会中国水产学会《科学养鱼》编辑部科研园地皱纹盘鲍脓疱病的研究１９９３年夏季，大连水产养殖公司槽式养殖的鲍发生脓疱病，死亡率高达５０—６０％。病症在鲍的足部肌肉上出现微隆起的白色疤，疤破裂后...     

皱纹盘鲍的疾病学研究进展

一、细菌病１．脓疱病皱纹盘鲍脓疱病的病原菌为河流弧菌。该病流行于我国北方沿海养殖地区，夏季发病频繁，死亡率高达５０％～６０％。病鲍足肌上有多个微隆起的白色脓庖，脓庖破裂后流出大量白色脓汁，并留下２～５厘米不等的深孔，足面肌肉呈现不同程度的溃烂。联合使用氯霉素、复方新诺明或氟哌酸进行药物防治效果较好。此外采用河流弧菌Ⅱ疫苗或噬菌体防治脓疱病，明显提高了成活率。２．脓毒败血症皱纹盘鲍脓毒败血症的病原菌为坎氏弧菌，存在于血淋巴液中而遍布全身各组织、器官，通过分泌胞外酶，破坏正常的组织结构而致鲍死亡，该…     

专题讲座鳖的养殖

第六讲鳖的健康养殖和病害预防近年来，由于多种原因，致使鳖病的发生率越来越高，暴发型疾病也日益增多。在养殖较密集地区发病率可达４０％～５０％，死亡率高达２０％～３０％，对养鳖业的发展构成了严重威胁。一、鳖病的诱发因素鳖病的发生是环境条件、养殖对象（宿主...     

浅谈鱼类鳃病及其防治措施

近年来随着水产养殖业的迅速发展，养殖逐渐向高密度、集约化方式发展。养殖中各种病害危及到水产业的生产，影响产量和经济收入。鳃病是常见的鱼病。常与细菌性肠炎病，赤皮病并发。发病严重的鱼类往往死亡率高达40％（草鱼达60％以上），严重影响集约化、高密度水产养殖的进一步发展。现就几年鱼类鳃病在我县内发生流行情况和防治措施总结如下：     

斑节对虾“红体病”细菌性病原的初步研究

从患“红体病”的斑节对虾中分离到８个菌株,通过致病力试验证实其中两个菌株是引起斑节对虾“红体病”的主要病原,使对虾死亡率分别达到７０％和９０％。根据生化试验,确定这两个菌株分别是嗜水气单胞菌和副溶血弧菌。抗药性实验的结果表明,嗜水气单胞菌菌株对强力霉素较为敏感,副溶血弧菌菌株对氟哌酸、红霉素、青霉素和强力霉素较为敏感。     

对斑节对虾白斑病治疗的方法与体会

白斑病，是斑节对虾养殖中的主要病害之一。近年来，其危害性越来越大。今年在我省夏季放养的斑节对虾中，此病大面积发生，给养虾生产造成了严重的损失。如汕尾市放养的近700公顷斑节对虾，此病迅速蔓延，发病率高达80％，而且病虾死亡率很高，不少虾池高达100％。为了探索有效的治疗方法，我们认真调查研究了白斑病的症状和病因，     

“正大模式”助虾农增产增收

中山南美白对虾养殖达12万多亩，年产值约20亿元，是水产养殖的支柱产业。近两年，正大集团优质南美白对虾虾苗抢摊登陆中山，并以养殖成活率超80％，单造亩产800至1000斤的业绩让广大备受虾苗、虾病困扰的虾农眼前一亮。苗好虾成，尽管每万尾苗价高达200元，是普通苗的四五倍，但虾农仍，争相选购正大虾苗养殖，以求突出对虾养殖“重围”。     

广东水产养殖病害测报情况及预报（2010年10月）

10月病害发生情况 根据我省各测报点本月水产养殖病害监测数据分析，10月份监测到的主要病害有鱼类出血病、烂鳃病、赤皮病、肠炎病、细菌性败血症、罗非鱼链球菌病、溃疡病、车轮虫病、指环虫病、锚头鳋病、斜管虫病、刺激隐核虫病、本尼登虫病、鳖疖疮病和红底板病、对虾白斑病、红腿病、桃拉病、不明病因病和固着类纤毛虫病。潮州和湛江市海水网箱养殖区海水鱼刺激隐核虫病发病较严重，部分地区发病率高达70％、死亡率达到60％。     

肠型点状气单胞菌和鱼害粘球菌的融合子特性研究

为了探索病原菌融合疫苗制备的可行性及其理论基础，查明鱼类病原菌融合子的遗传规律，本研究对草鱼肠炎病和烂鳃病病原的融合子特性进行了研究，结果表明：筛选的融合子菌株菌体大小、酶类性状及生理生化指标介于两亲本菌株之间；融合子菌株具有致病性，用融合菌株制成灭活抗原进行抗原性研究，免疫保护率达74．9％和75．5％，抗体效价于第4周达到峰值，分别为1：322．5和1：435．5。     

羊传染性脓疱病防治

正羊传染性脓疱病是一种传染性疾病,俗称"羊口疮"。特征是患羊口唇等部位皮肤黏膜形成丘疹、脓疮、溃疡以及疣状厚痂、觅食困难、逐渐消瘦,部分病羊继发其他疾病死亡,主要危害羔羊,一旦羊群发生本病,发病率可高达100%,将带来较大的损失。1临床症状羊传染性脓疱病的潜伏期为4~     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

Evaluation of a Fast Method Based on the Presence of Two Restriction Sites in the Mitochondrial ND5 (mt ND5) Gene for the Identification of Scomber Species

The purpose of this work was to evaluate the suitability of a method based on the presence of two restriction sites (for Hae III and Hindf I) in the mitochondrial NADH dehydrogenase subunit 5 (mt ND5) gene to identify Scomber species. The evaluation was performed on 144 reference and market samples by sequencing of the entire 505-bp fragment of the mt ND5 gene and of a 464-bp fragment of the Kocher fragment of the cytochrome b gene (mt Cytb). Sequence analysis of any of the two fragments allows the identification of each of the four Scomber species, but S. japonicus and S. colias had the same restriction sites at the ND5 amplicon and would not have been differentiated by this analysis. Similarly, loss of the Hae III site in some S. scombrus individuals would have misidentified them as not being Scomber. All the market products were correctly labeled except one acquired in Spain labeled as originating in the Atlantic and containing S. japonicus.     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.