Procambarus clarkii Girard as a vector for the crayfish plague fungus, Aphanomyces astaci Schikora

Abstract. Procambarus clarkii Girard, a native freshwater crayfish species of Lousiana, USA, was found to harbour the crayfish plague fungus, Aphanomyces astaci Schikora, in its cuticle as a benign infection. Under certain conditions, P. clarkii dies as a result of this parasite, and the A. astaci infection then becomes acute and can be transmitted to Astacus astacus (L.).
Therefore, it is now shown that at least three different species of North American crayfish ( Pacifastacus leniusculus Dana, Orconectes limosus Raff, and Procambarus clarkii Girard) can carry the crayfish plague fungus, A. astaci , can transfer the disease to other crayfish species, and under certain circumstances can die of its own infection.     

The present situation of freshwater crayfish, Astacus leptodactylus (Eschscholtz, 1823) in Turkey

The only native crayfish species in Turkey, Astacus leptodactylus, is widely distributed in lakes and ponds in many parts of the country. Its distribution area was considerably expanded in Turkey after 1985 because of its commercial importance and declined catches from traditional good fisheries. Although consumption of A. leptodactylus has always been very low in Turkey, it was exported to western Europe until 1986. Due to over-fishing, pollution and a disease (crayfish plague), the total production decreased dramatically to 200 from 5000 tonnes annually. In recent years (1991–1998), there has been a gradual increase in the production of crayfish in Turkey from 320 to 1500 tonnes, but plague is still present.     

中草药对雏鸭病毒性肝炎的防治研究

自制中药“鸭肝灵”散剂防治雏鸭病毒性肝炎试验结果显示:实验室对试验雏鸭攻毒试验中,预防保护率为85%,治疗保护率为80%;临床试验中,预防保护率为83.8%,治疗保护率为80.7%,仅次于鸭病毒性肝炎高免卵黄抗体的防治水平。试验结果表明:用中药散剂“鸭肝灵”防治雏鸭病毒性肝炎具有临床推广应用价值。     

The harvest of the freshwater crayfish <Emphasis Type="Italic">Astacus leptodactylus</Emphasis> Eschscholtz in Turkey: harvest history,impact of crayfish plague,and present distribution of harvested populations

This review focuses on the present distribution of populations of the crayfish Astacus leptodactylus that are harvested in Turkey. It also examines the history of this harvest and the impact that crayfish plague has had on them. Crayfish plague, caused by the fungus-like organism, Aphanomyces astaci Schikora, 1906, is a severe parasite of freshwater crayfish and has caused a lot of damage to A. leptodactylus populations in Turkey since 1984. Turkey was the largest provider of A. leptodactylus to Western Europe from 1970 (or possibly earlier) until 1986. For example, the peak production was reached in the early 1980s, with over 5,000 tonnes being exported in 1984. On the other hand, as a result of the crayfish plague the harvest of A. leptodactylus was reduced severely in most populations in Turkey after 1985. The harvest was only 320 tonnes in 1991. After the occurrence of crayfish plague in Turkey, in order to increase crayfish production uncontrolled A. leptodactylus stockings have been carried out in many waterbodies throughout Turkey. These introductions have caused an increase in the number of A. leptodactylus populations, but exploitation of A. leptodactylus is still under the pressure of the plague, although there has been a steady increase in crayfish production in recent years. The harvest increased to 2,317 tonnes in 2004. Fortunately, among those populations affected by crayfish plague, large amounts of A. leptodactylus can still be harvested from three lakes, ?znik (Bursa), E?irdir (Isparta) and Çivril (Denizli). Thus, it seems that A. leptodactylus has a degree of resistance to crayfish plague. It is therefore interesting to investigate the resistance of A. leptodactylus caught from these populations to crayfish plague.     

鸡产蛋下降综合征灭活苗生产工艺的探讨

通过用不同日龄的鸭胚接种EDS种毒,采用不同的孵化温度,比较鸭胚接种日龄及不同的孵化温度对抗原收获量及血凝价的影响。结果显示,用9日龄鸭胚接种明显优于其他日龄的鸭胚,抗原收获量及血凝价均达到较高水平;改变孵化温度(37～38℃),对鸭胚收获量及HA不会造成大的影响。     

三角帆蚌瘟病的组织病理研究

对健康及患瘟病三角帆蚌的１３种脏器组织作了系统的形态结构观察和组织化学分析，结果表明，三角帆蚌瘟病的组织病理变化主要集中在病蚌的肝脏、胃和直肠等组织。病毒侵袭蚌体后，肝脏的吸收细胞、未成熟细胞以及胃、直肠的纤毛上皮细胞内出现病毒包涵体，ＤＮＡ和ＲＮＡ等正常代谢受到抑制，ＡＫＰ和ＡＣＰ酶的活性和分布发生异常，细胞内消化作用受阻，最后病变细胞解体，导致肝脏、胃和直肠等的广泛受损。病蚌因消化系统坏死和消     

A tentative new species Aphanomyces fennicus sp. nov. interferes with molecular diagnostic methods for crayfish plague

Several isolates of an unknown oomycete resembling the genus Aphanomyces were obtained into laboratory culture from samples of noble crayfish (Astacus astacus) in 2016–2017. The crayfish were kept in cages in connection with a study on an eventually persistent crayfish plague infection in a small Finnish lake, following an acute episode of the disease in 2010. Despite the close resemblance of the isolates to the causative agent of crayfish plague, Aphanomyces astaci, and the positive results obtained in OIE recommended A. astaci‐specific ITS‐based conventional PCR and qPCR molecular assays, the isolates can be distinguished from A. astaci by morphological features concerning hyphal structure and chlamydospore formation, as well as using the randomly amplified polymorphic DNA‐polymerase chain reaction (RAPD‐PCR) method, microsatellite‐based genotyping, the pathogenicity test and phylogenetic analysis based on ITS sequencing. The name Aphanomyces fennicus sp. novum is proposed for this close relative of A. astaci. The detection of this tentative novel species giving false‐positive results in existing diagnostic assays for the crayfish plague highlights the importance of careful interpretation of the results from molecular methods, especially concerning crayfish with low‐level infections, excluding the possibility to verify the results from clinical or sequencing data.     

三角帆蚌肝脏瘟病感染期抑制性消减cDNA文库的构建与分析

采用抑制性消减杂交技术构建了三角帆蚌肝脏瘟病感染期抑制性消减cDNA文库。经检验，差异表达基因均被富集了 2¹⁰倍左右，证明构建的 cDNA 消减文库具有很强的消减效率。PCR 鉴定发现，在随机挑取的阳性克隆中，95% 的克隆均含有 0.2～1.0 kb 的插入片段，这些片段可能是三角帆蚌瘟病病毒感染后差异表达基因的cDNA片段。测序共获得 214 个有效 cDNA 序列，分别属于8 大类，共 98 个基因。其中细胞分裂基因 2个、细胞结构与运动基因 9 个、代谢基因 10 个、信号传导基因 7 个、细胞防疫基因 10 个、基因与蛋白表达基因 20 个、未知功能蛋白基因 26 个，GenBank中找不到任何同源序列的基因 14 个。结果说明，构建的差异表达cDNA文库，可较好地反映三角帆蚌瘟病病毒对三角帆蚌影响的基因信息。     

添加胰多肽对肉鸭生产性能和消化机能的影响

胰多肽(pancreation polypeptide,PP)是胰脏胰多肽细胞分泌的一种多肽类激素。为了研究胰多肽对肉鸭生产性能和消化机能的影响,实验通过从肉鸭小肠中提取PP粗品,并对其进行纯度鉴定,之后添加到肉鸭体内,产生动物模型,以进行动物实验。具体方案如下:100只肉鸭被随机分为5组,每组20只。Ⅰ组为对照组,每天饲饮自来水。Ⅱ、Ⅲ组分别饲饮剂量为0.58mg/d的PP粗品及剂量为0.29mg/d的PP纯品。Ⅳ、Ⅴ组分别于每周颈部皮下注射0.24mg/只的PP粗品及0.12mg/只PP纯品。饲养称重,宰杀后取小肠,对其进行处理后用紫外吸收法进行消化酶活力测定。结果表明:PP能促进肉鸭机体生长发育,促进体重增长,对肉鸭生产性能产生影响;对肉鸭小肠蛋白酶、淀粉酶和脂肪酶的活力有影响,从而影响消化机能。     

Comparative effects of various antibiotics, fungicides and disinfectants on Aphanomyces invaderis and other saprolegniaceous fungi

Fifty-four isolates of various fish-pathogenic and saprophytic fungi were characterized in terms of their susceptibility to three antibiotics (penicillin, streptomycin and oxolinic acid), three fungicides (malachite green, hydrogen peroxide and sodium chloride) and three disinfectants (an iodophore, sodium hypochlorite and a solution of peracetic acid and hydrogen peroxide). Aphanomyces invaderis, the fungus associated with the Asian fish disease epizootic ulcerative syndrome (EUS); other Aphanomyces isolates from the similar conditions redspot disease (RSD) and mycotic granulomatosis (MG); and the crayfish plague fungus, Aphanomyces astaci, were more sensitive to most of the chemical agents than the other fungi tested. Two compounds currently being considered for use in aquaculture, hydrogen peroxide and Proxitane 0510, are shown here to have some potential for fungicidal treatments and disinfection, respectively. The implications of this study with respect to the isolation, treatment and control of A. invaderis are discussed.     

Phylogenetic analysis and molecular methods for the detection of lymphocystis disease virus from yellow perch, Perca flavescens (Mitchell)

Lymphocystis disease is a prevalent, non-fatal disease that affects many teleost fish and is caused by the DNA virus lymphocystis disease virus (LCDV). Lymphocystis-like lesions have been observed in yellow perch, Perca flavescens (Mitchell), in lakes in northern Alberta, Canada. In an effort to confirm the identity of the virus causing these lesions, DNA was extracted from these lesions and PCR with genotype generic LCDV primers specific to the major capsid protein (MCP) gene was performed. A 1357-base pair nucleotide sequence corresponding to a peptide length of 452 amino acids of the MCP gene was sequenced, confirming the lesions as being lymphocystis disease lesions. Phylogenetic analysis of the generated amino acid sequence revealed the perch LCDV isolate to be a distinct and novel genotype. From the obtained sequence, a real-time PCR identification method was developed using fluorgenic LUX primers. The identification method was used to detect the presence/absence of LCDV in yellow perch from two lakes, one where lymphocystis disease was observed to occur and the other where the disease had not been observed. All samples of fin, spleen and liver tested negative for LCDV in the lake where lymphocystis disease had not been observed. The second lake had a 2.6% incidence of LCD, and virus was detected in tissue samples from all individuals tested regardless of whether they were expressing the disease or not. However, estimated viral copy number in spleen and liver of symptomatic perch was four orders of magnitude higher than that in asymptomatic perch.     

重庆地区一例鹅感染鸭圆环病毒病的PCR诊断

利用PCR技术对重庆荣昌地区患病鹅进行圆环病毒检测的过程中,发现一例鹅感染鸭圆环病毒的阳性病例,说明水禽之间的圆环病毒可能存在交叉感染的现象。     

Extra small virus-like particles (XSV) and nodavirus associated with whitish muscle disease in the giant freshwater prawn, Macrobrachium rosenbergii

A disease of Macrobrachium rosenbergii, the giant freshwater prawn, farmed in China was recently recorded in Zhejiang, Jiangsu, Shanghai, Guangxi and Guangdong provinces. The clinical sign of the disease, which develops in post-larvae (PL), is a whitish appearance of the muscles, particularly noticeable in the abdomen. Mortalities may reach 100% in some hatcheries. Investigations by transmission electron microscopy after negative staining of diseased PL homogenates showed the presence of two types of viral particles: one, unenveloped, icosahedral in shape, 26-27 nm in diameter, the second, much smaller, about 14-16 nm in diameter, designated extra small virus particle (XSV). The large virus has a genome with two pieces of ssRNA (RNA-1 and RNA-2), of 3 and 1.2 kb, respectively. Hybridization tests confirmed that this large virus is closely related to M. rosenbergii nodavirus (MrNV) which was isolated from diseased prawns in a hatchery in the French West Indies. Its very small size and hypothesized biochemical and biological characteristics suggest XSV is a new type of crustacean virus. As XSV has always been found associated with the larger virus (nodavirus) and is located in muscle and connective cells of diseased animals, it could be an autonomous virus, a helper-type virus or a satellite-like virus.     

Detection and antigenic characterization of salmonid alphavirus isolates from sera obtained from farmed Atlantic salmon, Salmo salar L., and farmed rainbow trout, Oncorhynchus mykiss (Walbaum)

A simple method of detecting the presence of the salmonid alphaviruses (SAVs), salmon pancreas disease virus (SPDV) and sleeping disease virus (SDV), from serum samples is described. Using a 96-well tissue-culture plate format, test sera are diluted in medium and added to chinook salmon embryo (CHSE-214) cells. After incubation for 3 days at 15 degrees C, plates are fixed and stained using a monoclonal antibody (mAb)-based immunoperoxidase (IPX) detection system, and virus-infected cells are observed microscopically by white light. Application of this screening test, which is now used routinely in our laboratory in conjunction with an IPX-based virus neutralization (IPX-VN) test for detecting antibodies to SAVs, has resulted in the recovery of 12 additional isolates from salmon sera and four additional isolates from trout sera. A low level of antigenic variation was detected when these SAV isolates were investigated by indirect immunofluorescence using a panel of mAbs raised to reference SPDV and SDV isolates.     

Investigation of outbreaks of a novel disease, 'Sleepy Grouper Disease', affecting the brown-spotted grouper, Epinephelus tauvina Forskal

Abstract. A novel disease affecting the brown-spotted grouper, Epinephelus tauvina Forskal, described here as Sleepy Grouper Disease¹ (SGD), resulted in significant economic losses in some Singaporean marine net-cage farms from April to August 1992. Investigations suggested that the aetiological agent was a virus, probably introduced with imported groupers. The virus was provisionally identified as an iridovirus on morphological evidence. The disease caused extreme lethargy in affected fish with few visible external signs. Mortalities either occurred gradually over the week from onset of clinical signs, or over a shorter period and in large numbers if fish were stressed. Consistent tissue changes were seen by light microscopy in the spleen, heart and kidney of affected fish. Electron microscopy showed viral particles associated with damage to cell organelles. In an experimental infection, apparently healthy fish cohabiting with an infected fish developed similar lesions and died. The significance of SGD in grouper culture is discussed.     

Herpesvirus salmonis: pathological changes in parenterally-infected rainbow trout, Salmo gairdneri Richardson, fry

Abstract. After fry of rainbow trout, Salmo gairdneri Richardson, had been infected parenterally with Herpesvirus salmonis , moribund or freshly dead specimens were examined histopathologically. The virus produced a generalized infection, the first signs of which appeared after 2–3 weeks. Visceral and respiratory organs and the heart showed major pathological changes, and pancreatic syncytia were judged to be pathognomonic. Kidneys were prime targets for the virus and showed the highest levels of infectivity; lesser amounts of virus were present in the stomach, liver, and intestine. The virus did not spread by contact to produce clinical disease nor could disease or viral replication be induced by parenteral inoculation of yearling Oncorhynchus nerka (Walbaum).     

种属特异性PCR技术在检测鹅肥肝掺假中的应用研究

建立起一种用于检测鹅肥肝是否掺假的方法:种属特异性PCR技术。以鹅、鸭的12SrRNA基因序列设计特异引物,扩增目的片段分别为97bp和196bp。以三类温度处理和0.1%～100%的鸭肥肝掺假比例,分析方法的有效性和灵敏性。结果表明,这种方法的效果是不受样品被长时间加热的影响(高至100℃,10min);同时,即使当掺假比例只有0.1%时,仍能有效扩增出2特异条带。说明本方法适用于快速、准确地检测鹅肥肝掺假的需要。     

H5亚型禽流感灭活油乳剂疫苗对鸭的免疫试验

H5亚型禽流感(AI)油乳剂灭活疫苗接种成年鸭和幼鸭后,用ELISA法检测抗体消长规律,结果表明,AIVH5亚型灭活油乳剂疫苗两次接种可以有效地预防成年鸭,而一剂H5亚型AIV灭活油乳剂疫苗接种幼鸭后的免疫应答反应不好。     

Outbreak of betanodavirus infection in tilapia, Oreochromis niloticus (L.), in fresh water

A betanodavirus associated with a massive mortality was isolated from larvae of tilapia, Oreochromis niloticus , maintained in fresh water at 30 °C . Histopathology revealed vacuolation of the nervous system, suggesting an infection by a betanodavirus. The virus was identified by indirect fluorescent antibody test in the SSN1 cell line and further characterized by sequencing of a PCR product. Sequencing of the T4 region of the coat protein gene indicated a phylogenetic clustering of this isolate within the red-spotted grouper nervous necrosis virus type. However, the tilapia isolate formed a unique branch distinct from other betanodavirus isolates. The disease was experimentally reproduced by bath infection of young tilapia at 30 °C. The reservoir of virus at the origin of the outbreak remains unidentified. To our knowledge, this is the first report of natural nodavirus infection in tilapia reared in fresh water.