Post-epizootic surveys of waterfowl for duck plague (duck virus enteritis)

Surviving birds from nine duck plague outbreaks in urban and confined waterfowl were sampled for duck plague (DP) virus and DP antibody during 1979-86. Duck plague virus was found in combined oral and cloacal swabs of birds from three outbreaks, and DP-neutralizing antibody was demonstrated in some birds from all nine outbreaks. Greater prevalence of DP antibody and higher titers were found in survivors from confined populations than from free-flying urban populations. Free-flying waterfowl from within 52 km of four DP outbreak sites were also sampled; virus was not found in any birds, but DP antibody was found in urban waterfowl in the vicinity of an outbreak in Potterville, Michigan. No evidence of exposure to or shedding of DP virus in migratory waterfowl was found in two regions where DP appears enzootic in urban and confined waterfowl (Eastern Shore of Maryland and the vicinity of Sacramento, California).     

Diagnosis of duck plague in waterfowl by polymerase chain reaction

A recently developed polymerase chain reaction (PCR) assay was used for diagnosis of duck plague in waterfowl tissues from past and current cases of waterfowl mortality and to identify duck plague virus in combined cloacal/oral-pharyngeal swab samples from healthy mallards (Anas platyrhynchos) after a disease outbreak. The PCR was able to detect viral DNA from all the individual or pooled tissues assayed from 10 waterfowl, including liver and spleen samples from three Muscovy ducks (Cairina moschata domesticus) that did not yield virus isolates. The strong staining intensity of the PCR products from the waterfowl tissues indicated that large amounts of virus were present, even when virus was not isolated. Duck plague DNA was also detected in a cloacal swab sample from a wood duck (Aix sponsa) carcass submitted for diagnosis. The PCR assay identified duck plague DNA in 13 swab samples that produced virus isolates from carrier mallards sampled in 1981 after a duck plague die-off. The duck plague PCR clearly demonstrated the ability to quickly diagnose duck plague in suspect mortality cases and to detect virus shed by carrier waterfowl.     

PCR用于鸭瘟病毒诊断的研究

根据鸭瘟病毒UL6和UL7基因序列,设计合成了一对引物,以2株疫苗株、1株强毒株和1株山东分离株DNA为模板,进行PCR扩增,得到预期690bp的目的片段.将扩增的目的片段克隆到pMD18-T载体,经Amp平板筛选,HindⅢ、BamHⅠ双酶切鉴定,获得阳性重组质粒.对重组质粒进行序列测定,与参考序列比较,山东分离株与参考序列的同源性为99.7%,其余3株DPV与参考序列的同源性均为100%.应用PCR可检测人工感染和自然感染鸭瘟的组织中的鸭瘟病毒,表明PCR检测鸭瘟病毒具有很高的特异性、敏感性,该法能够用于鸭瘟急性及亚临床感染的检测与诊断.     

Identification of duck plague virus by polymerase chain reaction

A polymerase chain reaction (PCR) assay was developed for detecting duck plague virus. A 765-bp EcoRI fragment cloned from the genome of the duck plague vaccine (DP-VAC) virus was sequenced for PCR primer development. The fragment sequence was found by GenBank alignment searches to be similar to the 3' ends of an undefined open reading frame and the gene for DNA polymerase protein in other herpesviruses. Three of four primers sets were found to be specific for the DP-VAC virus and 100% (7/7) of field isolates but did not amplify DNA from inclusion body disease of cranes virus. The specificity of one primer set was tested with genome templates from other avian herpesviruses, including those from a golden eagle, bald eagle, great horned owl, snowy owl, peregrine falcon, prairie falcon, pigeon, psittacine, and chicken (infectious laryngotracheitis), but amplicons were not produced. Hence, this PCR test is highly specific for duck plague virus DNA. Two primer sets were able to detect 1 fg of DNA from the duck plague vaccine strain, equivalent to five genome copies. In addition, the ratio of tissue culture infectious doses to genome copies of duck plague vaccine virus from infected duck embryo cells was determined to be 1:100, making the PCR assay 20 times more sensitive than tissue culture for detecting duck plague virus. The speed, sensitivity, and specificity of this PCR provide a greatly improved diagnostic and research tool for studying the epizootiology of duck plague.     

The occurrence of virus enteritis (duck plague) in wild birds]

296 samples from wild birds of 15 species were incorporated into long term exploration of duck plague on ducks in farms. By using virological and serological standard methods 9 virus carriers and 20 serum samples showing positive antibody titers could be detected. The epidemiology as well as the relation of the incidence of duck plague in wild birds and farm poultry is discussed.     

地高辛标记核酸探针检测鸭瘟病毒

鸭瘟是鸭、鹅和其他雁形日禽类的一种急性、热性、啦血性传染病．特，征足流行广泛，传播迅速．发病率高和死亡率大。由于鸭瘟引起死亡、淘汰和产蛋下降，给发病地区的商品鸭和产蛋鸭造成很大的经济损失，目前．国内检症、诊断该病常用的方法有病毒分离、琼脂扩散试骑、酶联免疫吸附试验等。国内尚未见地高辛标记核酸探针检测鸭瘟病毒的报道。     

Detection of duck plague virus by reverse passive hemagglutination test

A reverse passive hemagglutination (RPHA) test was developed to detect duck plague virus (DPV). The technique used sheep erythrocytes stabilized with formaldehyde and pyruvaldehyde and coated with immunoglobulin G (IgG) containing anti-DPV antibody prepared from antiserum produced in sheep. Optimum coating of stabilized erythrocytes occurred at 25 C and pH 4.0 with a concentration of IgG of 20-40 micrograms/ml and a 90-min incubation period. The coated cells were stable for 40 days when stored at 4 C or for at least 4 months (the longest period tested) when frozen at -70 C or -196 C. The RPHA test was conducted at 25 C and read after 3 hours. The high specificity of the test is indicated by the absence of cross-reactions with heterologous virus strains, with specimens prepared from normal duck livers, and with normal chicken embryo chorioallantoic fluid, as well as by the inhibition of hemagglutination only with DPV antiserum. The RPHA test detected six strains of DPV in all virus-containing specimens as well as the immunofluorescence (IF) test did; however, conventional plaque assays (PA) failed to detect virus in five specimens that contained three non-plaque-forming strains of DPV. The mean quantity of DPV that could be detected in the RPHA test was 25 plaque-forming units or 65 fluorescent units per ml. Although the RPHA test was less sensitive than either the PA or the IF test, there was a positive correlation in the titers of DPV antigens between all three tests. The RPHA test is a rapid, simple procedure that is sufficiently sensitive for diagnostic detection of DPV in acute infections, especially in tissues of ducks dying of the disease.     

鸭瘟病毒的分离和鉴定

1999年 8月广西玉林的养鸭大户送来一批一周龄左右的死亡雏鸭 ,称其养的 2 0 0 0多只雏鸭死亡过半 ,药物治疗不能控制病情。经临床剖检病变很象小鸭肝炎 ,我们采集了几份死鸭肝病料进行分离鉴定 ,现将结果报告如下。1　试验材料和方法1 .1　材料鸭瘟病毒阳性血清、Ⅰ型鸭肝炎病毒阳性血清由中国农业大学苏敬良博士惠赠。鸭胚与2日龄雏鸭购自本市健康鸭场孵化场。1 .2　病料处理对病鸭的肝脏先进行细菌分离 ,镜检。然后按常规方法作成 1 :5乳剂 ,离心取上清液 ,检验无菌后 ,-2 0℃保存备用。1 .3　病毒分离将处理好的病料经尿囊腔接种 1 1日…     

Laboratory confirmed outbreaks of duck virus enteritis (duck plague) in the United Kingdom from 1977 to 1982

From 1977 to 1983 the Central Veterinary Laboratory, Weybridge confirmed 19 outbreaks of duck virus enteritis in the United Kingdom. All the outbreaks involved collections of captive waterfowl and there were no reported cases in commercial ducks. In many instances the disease was associated with contact with migrating waterfowl, particularly male mallards (Anas platyrhynchos). Muscovy ducks (Cairina moschata) and related species appeared to be particularly susceptible. The most sensitive system for isolating the virus was muscovy duck embryo tissue cultures. The duckling inoculation test was found to be the most reliable method of confirming the disease.     

Molecular evidence for transplacental transmission of Theileria equi from carrier mares to their apparently healthy foals

The intra-erythrocytic parasite Theileria equi is one of two tick-transmitted causative agents of equine piroplasmosis. Piroplasms of T. equi can be transmitted across the equine placenta and once a horse is infected, it appears to remain a lifelong carrier, since anti-theilerial drugs suppress but do not eliminate the parasite. Carrier mares may transmit the organism to their offspring and this may result in abortion or neonatal piroplasmosis, but observations by some researchers suggest that foals may be born as carriers yet remain apparently healthy. Using a T. equi-specific oligonucleotide probe, we have determined that transplacental transmission occurs early in equine foetal development and that carrier mares may give birth to healthy carrier foals. Investigation of parasite levels and the effect of maternal colostrum on the newborn suggests that colostral T. equi antibody may act to suppress parasitaemia in the newborn, reducing the incidence of clinical neonatal piroplasmosis.     

间接ELISA检测新型鸭瘟病毒抗体

以50%饱和度的硫酸铵粗提病毒,再经Sephadex G-200过柱层析纯化了新型鸭瘟病毒,以此作为包被抗原,并用自制油苗免疫雏鸭,获得了高效价的血清抗体,又经过各种条件优化,建立了检测血清抗体的间接ELISA方法.经对不同发病日龄和免疫油苗后雏鸭的血清检测,证明该检测方法有很高的敏感性、特异性和重复性,可作为快速诊断该病的一种可靠方法.     

鸭瘟病毒强毒株感染SPF鸭后动态病理组织学变化

用鸭瘟病毒(Duck plague virus,DPV)人工感染2月龄SPF鸭,定期剖杀,经聚合酶链反应(PCR)检测为鸭瘟后,对各组织器官的病理组织学变化进行观察,并进行血常规和血液生化指标检测.结果显示,人工感染后24 h,试验鸭中枢免疫器官胸腺、法氏囊表现为淋巴细胞数量减少,组织间隙增大;肝脏、脾脏组织病变较为严重,大部分组织器官均出现程度较轻的病理变化.感染后48～96 h,中枢免疫器官的淋巴细胞极度减少、网状细胞增生、组织器官结构模糊不清,严重充血、出血;其余组织器官出现细胞变性、出血等不可逆病理变化.感染后120 h,组织细胞变性、坏死,出现大片坏死区.点眼滴鼻组鸭感染DPV后组织学变化与皮下注射组相似,只是发生的时间偏后约24～48 h.对照组鸭病理组织学观察未见损伤.WBC、HGB、AST、ALT等发生显著变化.结果表明,接种DPV强毒感染鸭的组织器官严重受损,特别是免疫器官,甚至会引起免疫抑制.     

不同条件对鸭瘟病毒感染细胞蛋白质组二维电泳分析结果的影响

本研究以鸭瘟病毒感染鸭胚成纤维细胞为材料,围绕影响二维电泳因素进行全面探讨,以建立和优化鸭瘟病毒感染细胞蛋白质组二维电泳模型.结果表明,样品经过冷丙酮处理,水化液DTT浓度为30 mmol/L都有利于等电聚焦;采用PH5～8 IPG窄胶条和混合两性裁体电解质pH3～10/pH5～8为2/1比pH3～10 IPG宽胶条和单一两性载体电解质PH3～10分离蛋白时,各蛋白点间距较大,分辨率高,更有利于显示低丰度蛋白点;1.5 mg的蛋白上样量偏大,2～DE图像出现拖尾和水平条纹,部分相邻高丰度的蛋白重叠,且还掩盖了低丰度蛋白点.PDQuest7.40软件分析显示:17 cm PH5～8 IPG胶条电泳鸭瘟病毒感染细胞蛋白质组,银染可获得1 253个蛋白点,而考染却检测到388个蛋白点;重复试验仍获得清晰、稳定的2-DE图像,同一样本不同时期,考染可获得约348、331个蛋白点,蛋白点匹配率达88%,表明了鸭瘟病毒感染细胞蛋白质组二维电泳模型稳定、分辨率高、重复性好,为鸭瘟病毒蛋白组的进一步研究和新蛋白的发现提供了重要的研究方法.     

鸭瘟病毒部分基因的克隆与序列分析

用BamH、EcoR、Hind、Pst、Sal 5种限制性内切酶消化鸭瘟病毒基因组DNA,回收2~6 kb片段连入pUC19载体,构建了鸭瘟病毒基因组部分文库。选取部分克隆进行序列测定,获得5个UL片段基因,分别为UL33、UL34、UL45、UL46和UL47。序列比较显示,它们与α-亚科疱疹病毒其他成员相应基因具有不同程度的同源性。这是国内外对鸭瘟病毒以上基因序列的首次报道。     

鸭瘟病毒在雏鸭体内的动态定量分布及其潜伏部位研究

为研究鸭瘟病毒的组织细胞嗜性及其潜伏部位,采用real-timePCR技术对人工感染后病毒的组织器官分布进行了动态定量分析。结果表明,鸭瘟病毒在肝、脾、外周血淋巴细胞、法氏囊、三叉神经节、肾、肺和心脏等均能增殖;动态定量分析发现,随疾病发展各器官病毒荷载量不断上升,至死亡时达到顶峰;肝、脾中病毒载量高,出现时间早,持续时间长;耐过鸭多数组织器官中病毒逐渐消失,但三叉神经节及外周血淋巴细胞在感染后38d仍能检测到低拷贝病毒DNA,表明除三叉神经节外,外周血淋巴细胞也很可能是潜伏部位。     

Isolation of an apathogenic immunogenic strain of duck enteritis virus from waterfowl in California

A herpesvirus isolated from waterfowl dying of duck enteritis (DE) was tentatively designated the Sheridan-83. It was serologically related to the original Holland and Lake Andes (LA) strains of duck enteritis viruses (DEV). Other biological characteristics indicated that the Sheridan-83 was more closely related to the Holland strain than to the LA virus. The Sheridan-83 was nonpathogenic to ducks, and ducks inoculated with this virus developed resistance to challenge with the virulent strain LA.