Effect of Indomethacin on the Development of Proliferative Gill Disease

Abstract

After parenteral treatment with the cyclooxygenase inhibitor indomethacin, channel catfish Ictalurus punctatus were exposed to mature spores of an Aurantiactinomyxon sp. demonstrated to be the etiological agent of proliferative gill disease (PGD). Fish that received indomethacin at a dose of 2.0 or 5.0 mg/kg body weight within 0.5 h before exposure to the myxozoan and again at 24 h postexposure had significantly (P < 0.05) less severe gill lesions 7 d after exposure than fish that received the drug vehicle alone. Fish that received 0.5 mg indomethacin/kg had moderately severe lesions. All fish were confirmed to be infected with the organism associated with PGD by microscopic examination of gills 4 or 7 d postexposure. These results suggest that products of the cyclooxygenase pathway (e.g., prostaglandins) participate in the pathophysiologic host response to PGD.     

Experimental Induction of Proliferative Gill Disease in Specific-Pathogen-Free Channel Catfish

Abstract

Specific-pathogen-free channel catfish Ictalurus punctatus were exposed to sediment and mud from a pond containing channel catfish with proliferative gill disease. In one experiment, fish were to exposed to mud and sediment for 2 months in water maintained at 19°C. Fish were necropsied weekly, and certain tissues were examined histologically and ultrastructurally. Four trials were conducted with sediment samples from different epizootics of proliferative gill disease. In a second experiment, fish were exposed to sediment for 7 d in water maintained at 16, 19, or 26°C; the fish were then moved to clean water held at 16, 19, or 26°C. Fish were necropsied before transfer to clean water and weekly thereafter for 2 months. Channel catfish held at 19°C developed proliferative gill disease within 2 d of exposure to sediment. Primary cells of a uninucleate myxosporean parasite were present in the gills at the base of lamellae. These developed into plasmodia with numerous secondary cells, and some primary cells disintegrated, releasing their internal secondary cells. Similar development was observed in internal organs 1 week after appearance of the parasite in gills. Complete sporogony did not occur over the 2 months of this study. Plasmodia became necrotic and were not detected after 60 d. In fish exposed to sediment for 7 d at 16, 19, and 21°C, similar organisms were detected, but clinical disease occurred only at 19 and 26°C. Proliferative gill disease may be attributed to extrasporogonic stages of a myxosporean resembling Sphaerospora spp.     

Induction and Evaluation of Proliferative Gill Disease in Channel Catfish Fingerlings

Abstract

Proliferative gill disease (PGD) was first reported in channel catfish Ictalurus punctatus at commercial farms in 1981 and is caused by the myxozoan parasite Henneguya ictaluri. The disease affects the gills and is characterized by severe branchial inflammation, epithelial hyperplasia, lamellar fusion, and lysis of chondrocytes. Presumptive diagnosis is based on the presence of lytic areas in the cartilage of the primary lamellae on microscopic examination and is confirmed histologically by the presence of the organism. In these trials, PGD was induced by exposing channel catfish fingerlings to fresh or aged infectious water collected from a pond containing fish diagnosed with severe PGD. The severity of disease was graded by histological scoring and microscopic examination of wet mounts to determine the percentage of gill filaments containing chondrolytic lesions. Exposure of fish to infectious pond water was shown to produce pathological lesions consistent with PGD, and the percentage of gill filaments containing chondrolytic lesions was positively correlated with histological scoring of gill pathology. The number of trophozoite stages in the gills was shown to increase with the severity of the disease. In most cases, however, parasitic cells were not observed in tissue samples with chondrolytic lesions during the early stages of infection. These observations indicate that pathology and lysis of chondrocytes can occur prior to detection of the organism by histopathology. Exposing fish to infectious pond water that was aged for 1 d produced negligible gill pathology and implies that the infectivity of the H. ictaluri actinospore stage is short lived. Removing fish from the source of infection promoted repair of damaged gill tissue; within 14 d of fish transfer to clean water, gill pathology associated with the acute infection was negligible.     

Communications: Experimental Production of Proliferative Gill Disease in Channel Catfish Exposed to a Myxozoan-Infected Oligochaete,Dero digitata

Abstract

Specific-pathogen-free fry of channel catfish Ictalurus punctatus raised in well water were exposed to Dero digitata (an oligochaete) collected from ponds where catfish have had proliferative gill disease (PGD) and where D. digitata is known to be infected with the triactinomyxid myxozoan Aurantiactinomyxon sp. These fry developed gill lesions and parasites characteristic of PGD. Fry exposed to suspensions of mature Aurantiactinomyxon spores obtained from squashes of infected D. digitata also developed PGD. Fry exposed to oligochaetes other than Dero spp., non-oligochaete benthic macroinvertebrates, or suspensions of squashes of D. digitata without identifiable myxozoans did not develop PGD.     

Small Subunit rRNA Gene Comparisons of Four Actinosporean Species to Establish a Polymerase Chain Reaction Test for the Causative Agent of Proliferative Gill Disease in Channel Catfish

Abstract

Proliferative gill disease (PGD) causes high morbidity and mortality in cultured channel catfish Ictalurus punctatus. The presence of the myxozoan Aurantiactinomyxon ictaluri (class Actinosporea) is strongly associated with PGD. This parasite, shed as an actinospore from the aquatic oligochaete Dero digitata, infects channel catfish by an undetermined route. Several other actinosporeans have been identified that are shed from D. digitata isolated from catfish ponds, including those designated A. mississippiensis, Helioactinomyxon sp., and the actinospore stage of Henneguya exilis. By the use of multiple sequence alignment of polymerase chain reaction (PCR)-amplified small subunit ribosomal RNA (SSU rRNA) genes of A. ictaluri, A. mississippiensis, and H. exilis, we identified two variable regions. The largest variable region was PCR amplified, sequenced from the Helioactinomyxon sp., and used in addition to the other three sequences in multiple-sequence alignment comparison to develop PCR primers specific for A. ictaluri. This PCR specific for A. ictaluri produced 104-base-pair products from a plasmid clone containing the SSU rRNA gene of A. ictaluri, spore DNA of A. ictaluri, and DNA prepared from channel catfish gill and D. digitata infected with A. ictaluri. The PCR assay was able to detect as few as 100 copies of the cloned gene. There was no detectable product from the genomic DNA of H. exilis, A. mississippiensis, or Helioactinomyxon sp., specific pathogen-free channel catfish gill, and noninfected D. digitata. The PCR assay will be useful as a diagnostic tool for PGD in channel catfish and will aid in the elucidation of the life cycle of A. ictaluri.     

Communications: Metastatic Gill Lesions Secondary to Cardiac Hemangioendotheliosarcomas in the Teleost Fish Mangrove Rivulus

Abstract

Gill neoplasms have been infrequently described for teleost fishes. Nine of 51 cases of primary cardiac endothelial cell neoplasms of a teleost fish species, mangrove rivulus Rivulus marmoratus, also possessed endothelial cell neoplasms in their gills. These neoplasms occurred in the afferent arterioles of the gill filaments. They were made up of round cells or spindle cells that had nuclei similar to typical endothelial cell nuclei. The large gill neoplasms, with more anaplastic cells, penetrated the walls of the gill arterioles and invaded adjacent gill tissues. Supporting evidence for the metastatic nature of these gill neoplasms includes the following: (1) they were secondary in timing, numbers, and size to the advanced sarcomas of the heart; (2) cell phenotypes of both gill and cardiac neoplasms were similar in cytoplasmic and nuclear features; (3) the cardiac neoplasms appeared to be shedding neoplastic endothelial cells into the lumen of the bulbus arteriosus with a direct route via the circulation of the ventral aorta to the afferent arterioles of the gills; and (4) direct evidence that the gill neoplasms arose from gill endothelium was lacking.     

Observations on the Occurrence of Bacterial Gill Disease and Amoeba Gill Infestation in Rainbow Trout Cultured in a Water Recirculation System

Abstract

Spontaneous outbreaks of bacterial gill disease (BGD) occurred in 17-44-g rainbow trout Oncorhynchus mykiss after they were placed in a water recirculation system. In each of five groups stocked from September 1991 through July 1992, BGD occurred within 6–8 d after stocking. In each instance, BGD was followed by a secondary amoeba infestation. The spontaneous BGD outbreaks did not occur among previously stocked groups that had recovered from earlier BGD disease outbreaks. Examination of gill tissue by Gram stain and indirect fluorescent antibody technique showed increased numbers of filamentous bacteria associated with BGD after the rainbow trout were stocked into the system. Bacterial numbers decreased after a 1-h treatment with chloramine-T at concentrations of 9–15 mg/L but increased within 2 d after treatment. Although the chloramine-T treatments controlled mortality related to BGD, the amoeba infestation persisted. Histological examination of gills showed some focal hyperplasia before the rainbow trout were placed into the recirculation system, but hyperplasia became more extensive and lamellar fusion and mild telangiectasis developed within a week after placement in the system. The density at which the fingerling rainbow trout were stocked and the suspended solids present in tank water may have contributed to the BGD outbreaks. Exposure of juvenile rainbow trout to tank water from the recirculation system before they were placed into the system did not afford them protection against BGD after stocking.     

Hatchery Efficacy Trials with Chloramine-T for Control of Bacterial Gill Disease

Abstract

Three hatchery trials were carried out to determine the efficacy of chloramine-T for the control of bacterial gill disease in rainbow trout Oncorhynchus mykiss, ranging in weight from 2.5 to 54 g. In each trial, we used a single flow-through treatment of 8.5 mg chloramine-T/L. The single treatment provided effective control in all three trials; however, results were best when treatment was begun in the early stages of an outbreak. A second or third treatment may be required if an outbreak is in an advanced stage or if fish are under stress.     

草鱼细菌性烂鳃病病原菌的分离及其特异性卵黄抗体的初步研究

试验从患典型烂鳃病草鱼病变部位分离到1株柱状黄杆菌(FC-3株),采用0.4%甲醛灭活制成免疫原,接种健康120日龄桃源蛋鸡,收集鸡蛋并提纯卵黄抗体(IgY),并以此IgY为基础建立间接ELISA方法。结果:用FC-3株制备的IgY经初步提纯后电泳分离可见重链和轻链2条蛋白条带,获得了IgY多克隆抗体。建立的间接ELISA方法检测柱状黄杆菌纯培养液的检出限值为1×10^7cfu/mL,抗原包被最佳浓度和抗体最佳工作浓度分别为1∶100和1∶512,辣根过氧化物酶标记兔抗鸡IgY最佳工作浓度为1∶4000。结论:建立的间接ELISA方法对柱状黄杆菌有明显的检测特异性,与其他菌株无交叉反应,重复性好。     

鱼类细胞肿大虹彩病毒病研究进展

鱼类细胞肿大虹彩病毒病在东亚和东南亚的真鲷、石斑鱼、大菱鲆、大黄鱼、鳜鱼等多种养殖鱼类中的频繁流行,致使感染鱼类出现大面积死亡,已成为危害养殖鱼类最严重的病毒病之一.文章综述了近年来鱼类细胞肿大虹彩病毒病的研究现状,重点介绍了该类疾病的流行病学、临床症状、组织病理学、分子生物学检测技术、病毒的传播途径、致病机制以及病毒的免疫防控等方面的研究进展,并对当前鱼类细胞肿大虹彩病毒研究中存在的问题进行了分析和展望.     

Factors Involved in the Dissemination of Disease in Fish Populations

Abstract

Infectious diseases have been observed in both human and animal populations for millenia. Unlike diseases of “higher” animals, the dispersal of disease in fish populations rarely has been studied quantitatively. However, the principles that govern the spread of diseases of humans and other mammals should, with modification, be applicable to the study of infectious diseases in fishes. Disease in populations is a dynamic phenomenon; fluctuations in prevalence and impact are dependent on the interactions among host, pathogen, and environment. Models of the dynamics of infectious diseases in salmon and other fishes can be constructed and refined to reflect the characteristics of diseases by integrating the most important factors in the process. Among the factors that have been shown to be important in other systems are the “contagiousness” of the pathogen (transmission coefficient, β), duration of infection, host population density, development of immunity, and efficacy of therapeutants.     

Blood Parameters and Immune Status of Rainbow Trout with Proliferative Kidney Disease

Abstract

Blood parameters, disease resistance, and the immune response were sequentially evaluated in rainbow trout Oncorhynchus mykiss with proliferative kidney disease (PKD). The fish were maintained under laboratory conditions, and the study group went through a full cycle of the disease. Hematological and serological changes occurred primarily in those fish with severe kidney lesions. Fish infected with the parasite that causes PKD demonstrated a greater resistance to bacterial challenge, and their immune responses were heightened when compared with those of uninfected fish. These data suggest that PKD alone is not a predisposing factor for secondary infections if the fish does not incur severe renal lesions.     

Cellular Inflammatory Response of Rainbow Trout to the Protozoan Parasite that Causes Proliferative Kidney Disease

Abstract

The cellular inflammatory response of rainbow trout Oncorhynchus mykiss (formerly Salmo gairdneri) to the myxozoan parasite PKX that causes proliferative kidney disease was investigated. The response was studied from 3 to 20 weeks after the fish were injected with infected kidney homogenate. Kidney samples were examined by light and electron microscopy. In contrast to most myxosporeans, PKX provoked a severe host response. Parasites were found in peritubular capillaries and sinusoids 3 weeks postinjection. The initial response to PKX was hemopoietic hyperplasia followed by a marked granulomatous nephritis that was resolved by termination of the study at 20 weeks postinjection. The macrophage was the predominant cell type involved in the inflammatory response to PKX. We presume that the macrophage effectively interrupts the development of PKX and eliminates the parasite from the host.     

养殖鱼类脂肪肝病的诊断和防治研究概况

经济鱼类的人工集约化养殖范围较广,养殖密度大,饲料投喂不当、营养失衡和渔药滥用都会诱发鱼类脂肪肝病。该病的表现形式多样,可通过表观诊断、剖检观察、显微观察、检测相关指标等方法对鱼类脂肪肝病做出临床诊断,在此基础上通过病理实验构建营养代谢性和化学性脂肪肝病模型,进一步探知脂肪肝病的病因、病理生理和判断药物疗效。对鱼类脂肪肝病防治效果显著的西药活性因子包括胆碱、蛋氨酸、磷脂、肌醇等,中药包括垂盆草、虎杖苷、蛇床子素、当归等,以及人工合成的壳聚糖等物质。今后应更加重视肝脏脂肪代谢机理的研究,为鱼类脂肪肝病确诊和治疗奠定基础。     

淡水鱼类线虫病的病原及其扫描电镜观察

从浙江省的窖湖、灵湖、凤湖等水库捕捞的大银鱼、花Hua、鸟鳢鱼、黄颡鱼、鲶鱼、沙塘鳢等6种鱼类体内获得大量的红色线虫，对其进行光镜和扫描电镜察，根据其形态特征和流行病学资料，鉴定为膨结科胃瘤线虫未定种(Eustrongylides sp．)。此线虫在大银鱼、花Hua、沙塘鳢体内寄生国内尚属首次报道。     

20味中药对鳗弧菌的药敏试验

鳗弧菌病是养殖及淡、海水水产动物的重要疾病之一。该病在全球范围内广泛发生,目前对该病的防制主要利用化学药品、抗生素或减活、灭活疫苗。通过20种中药对鳗弧菌抑菌、杀菌作用的研究,用2种常用抗生素类药物作为对照。结果表明,黄芩、白头翁、鱼腥草、五倍子、石榴皮4种中药对鳗弧菌的抑菌作用效果显著。     

Gill Reaction to Pollutants from the Tamiš River in Three Freshwater Fish Species,Esox lucius L. 1758, Sander lucioperca (L. 1758) and Silurus glanis L. 1758: A Comparative Study

The study evaluated the effects of waterborne pollutants from the Tami? River on gill histology and possible differences in gill reaction patterns between three freshwater fish species, pike Esox lucius L. 1758, pike‐perch Sander lucioperca (L. 1758) and wels catfish Silurus glanis L. 1758 from the Tami? River. Gills from analysed fish species showed moderate to intense histopathological alterations. The most frequent progressive alteration was hyperplasia of epithelium, whereas the most frequent regressive alteration was epithelial lifting. Circulatory disturbances were most often manifested in the form of hyperaemia. During comparative analysis, differences in gill indices, reaction and alteration indices, as well as in gill and filament prevalence between analysed species, were observed. Although all analysed fish species did show both progressive and regressive alterations, there was a significant difference in the level of expression of these reaction patterns. Gill index obtained for pike clearly stands out as the lowest. Wels catfish showed the highest progressive reaction index, significantly higher in comparison with the other two species (P < 0.05), while pike‐perch showed the highest regressive reaction index, also significantly higher in comparison with the other species (P < 0.001). These results may implicate species‐specific gill reactions and thus present a useful tool for better understanding toxic mechanisms of various pollutants.     

鱼源病原菌对氟喹诺酮类药物的耐药性分析

本试验旨在了解北京地区鱼源病原菌对氟喹诺酮类药物的耐药现状,提供氟喹诺酮类药物在防制鱼类疾病上合理规范使用的依据。从北京地区具有典型症状的病鱼脏器或病灶分离出16株病原菌,采用纸片扩散法检测病原菌对7种氟喹诺酮类药物的耐药表型,运用PCR法分析病原菌的喹诺酮类耐药基因gyrA、qnrA和qnrS的携带情况。结果表明,鱼源病原菌对氟喹诺酮的耐药基因阳性率显著高于耐药表型检出率,可能耐药基因检测比耐药表型检测更能推测病原菌的耐药现状。50%的病原菌至少耐受1种氟喹诺酮类药物,87.5%的病原菌至少携带1种喹诺酮耐药基因,显示北京地区鱼源病原菌对氟喹诺酮类药物已在基因水平呈现出严重的耐药,有必要严格控制此类药物在鱼类养殖上的应用。