鸡非典型性新城疫与大肠杆菌病混合感染的诊治

新城疫 (ND)是威胁我国养鸡业的主要传染病 ,病源是新城疫病毒 (NDV) ,虽然NDV只有一个血清型 ,其抗原性一致 ,但毒力差异较大 ,传统疫苗对流行毒株有一定保护力 ,且保护力在 55%以上 ,近年来新城疫的发生和流行日趋增加 ,我国自 1 996年以来也数次出现典型性新城疫的暴发。在生产中几乎所有的商品鸡均多次使用ND疫苗 ,但免疫鸡群仍屡次发病 ,因此 ,控制和减少免疫鸡群中ND强毒感染与传播成为我们鸡病防制工作中亟待解决的问题。奎屯及周边地区的养鸡户中也时常暴发鸡新城疫 ,这些发病鸡都做过ND免疫 ,发病多以非典型性新城疫为主 ,且…     

新城疫面面观 英特威(香港)有限公司技术服务部

在禽流感(AI)呈全球性流行的阴霾下,相信强调控制新城疫(ND)的重要性绝对有助于AI的控制,因为现场ND的控制尚存在值得改进之处。本文就与控制ND有关的问题简述于下,希望对大家有所帮助。1疾病ND是由NDV引起的一种高度传染性的禽病,各种家禽均可感染,其中鸡最易感。传染源是病鸡及带毒鸡,易感鸡王要通过呼吸道和消化道感染,人员、设备、饲料及饮水等也可机械性传播本病。2NDV的分型2.1致病型根据其所致症状可分为:嗜内脏速发型(vvNDV)、嗜神经速发型(nvNDV)、中发型、缓发型(多用于研制弱毒疫苗)及无症状肠型(多为肠道感染)等5种致病型。2.2基因型1998年有学者利用分子生物学方法将世界各地NDV主要分离株分为7种基因型、常用的ND LaSota(IV系)疫苗为基因Ⅱ型.而国际ND标准实验室的标准攻毒毒株Herts为基因IV型,疫苗与攻毒毒株基因型不吻合。1992年荷兰曾暴发ND,随后在孵化场对1日龄雏鸡强制性使用NobilisClone30进行喷雾免疫,很快便控制了疫情.引起此次疫情的NDV为基因Ⅶ型,而Clone30则为属于基因Ⅱ型的IV系类疫苗,流行毒株与疫苗所用毒株似乎也与基因型无关。因此,基因型概念在免疫保护谱上并无实质性意义。3何谓新城疫现场分离到HDV并非一定称为ND感染。据OIE的标准:①感染家禽的NDV,其IGPI≥0.7,即认为是NDV感染;②如副黏病毒I型在F2蛋白C端有多个(至少3个)碱性氨基酸和在117位点(F1蛋白的N端)出现芳香苯丙胺酸(F),则判定为ND感染,如标准②有异议,可返回标准①。对于ND疫苗,OIE建议:①生产活疫苗的NDV,其ICPI≤0.4;②生产灭活苗的NDV,其ICPI≤0.7NDI系苗其ICPI一般为1.2-1.6,鸡场使用I系苗免疫鸡群,根据OIE的标准这实际上是在人工感染NDV!因此建议禁止使用国外已明令禁用而国内仍广泛使用的NDI系苗。     

鸡毒支原体对NDV La Sota株免疫应答的影响

以鸡毒支原体NB72株或和R株对鸡先行人工感染,然后,与无支原体感染的对照鸡同样接种NDV La Sota株,观察NDV免疫应答动态。结果,支原体感染鸡群血清和气管中的NDV血凝抑制抗体效价,虽然比未接种支原体的鸡群低.但二者差异不显著(P>0.05).随后,通过攻击NDV强毒,不论先前经过或未经过支原体人工感染,ND免疫鸡全部被保护,且血清中NDV HI抗体效价均大幅度升高;未经ND免疫接种的对照鸡全部发病死亡,因此,鸡毒支原体NB72株或R株感染的鸡对NDV La Sota株的免疫应答无明显改变。最后就体内试验的结果进行了讨论。     

免疫鸡群中新城疫强毒感染流行趋势

新城疫 ( ND)仍是目前我国分布最广、危害最严重的禽病之一 [1] 。 ND的临诊表现差异很大 ,从不明显感染到高度致死不等 ,其严重程度主要取决于感染病毒的毒力和鸡群的免疫状态[2 ] 。虽然国内几乎所有商业鸡群均需多次使用 ND疫苗 ,但免疫鸡群仍屡屡发生 ND。因此 ,控制和减少免疫鸡群中 ND强毒感染与传播成为我国鸡病防制工作中亟待解决的问题 [3 ]。本试验运用 ND单抗酶联免疫试剂盒作为 ND流行病学调查手段 ,对华东地区部分免疫鸡群中 ND强毒感染进行监测 ,结合测定个体 HI抗体 ,探讨免疫鸡群中 ND强毒感染流行原因和趋势 ,为制…     

Immune protection assay of Newcastle disease live vaccine （LaSota Strain） against a genotype VII NDV isolate

从山东省发病鸡群分离鉴定了一株新城疫病毒（NDV）,命名为SDLY01。经蚀斑纯化后进行毒力测定和序列分析表明分离株SDLY01属于基因VII型NDV强毒。20只7日龄SPF鸡免疫新城疫活疫苗LaSota后14d分别用NDV标准强毒F48E8和分离株SDLY01攻毒,同时设同日龄SPF鸡为对照组,未免疫任何疫苗。攻毒后观察10d,免疫组在攻毒后食欲、精神均正常;对照组在攻毒后2～4d发病死亡,并表现ND典型的临床症状和病理变化。攻毒后第3、5、7、9d对免疫组试验鸡取喉头、泄殖腔棉拭进行病毒分离,F48E8攻毒组病毒分离均为NDV阴性,SDLY01攻毒组第5d病毒分离NDV阳性,第3、7和9d病毒分离阴性。本研究结果表明LaSota活疫苗对F48E8和SDLY01均能提供100％免疫保护,但不能完全抑制基因VIINDV分离株在体内的复制和排毒。     

新城疫LaSota活疫苗对基因Ⅶ型分离株的免疫保护性试验

从山东省发病鸡群分离鉴定了一株新城疫病毒(NDV),命名为SDLY01。经蚀斑纯化后进行毒力测定和序列分析表明分离株SDLY01属于基因Ⅶ型NDV强毒。20只7日龄SPF鸡免疫新城疫活疫苗LaSot a后14 d分别用NDV标准强毒F48E8和分离株SDLY01攻毒,同时设同日龄SPF鸡为对照组,未免疫任何疫苗。攻毒后观察10 d,免疫组在攻毒后食欲、精神均正常;对照组在攻毒后2～4d发病死亡,并表现ND典型的临床症状和病理变化。攻毒后第3、5、7、9 d对免疫组试验鸡取喉头、泄殖腔棉拭进行病毒分离,F48E8攻毒组病毒分离均为NDV阴性,SDLYO1攻毒组第5 d病毒分离NDV阳性,第3、7和9d病毒分离阴性。本研究结果表明LaSot a活疫苗对F48E8和SDLY01均能提供100%免疫保护,但不能完全抑制基因Ⅶ NDV分离株在体内的复制和排毒。     

鸡新城疫的流行与免疫

门诊病例统计表明，我国鸡群中ND的发病率仍非常普遍。近些年来，世界各地对NDV分离株的研究结果发现，其HN基因和F基因序列的某些位点发生的变化，致使毒株间的毒力差异较大，抗原性亦有差异，但其主要抗原表位未发生变化。山东家禽研究所禽病室对1998－1999年的6个NDV分离株做了比较研究，各毒株的毒力不同且都比经典的F48E9强，其中二个属基因Ⅶ型。但交叉免疫保护试验表明，用La Sota株弱毒苗及其灭活油乳苗免疫的鸡，在用这6个分离毒分别攻毒后，均有1005保护率。同样，用这6个分离毒制成的灭活油乳苗免疫鸡后，对经典毒E48F9亦产生100％保护率。这表明，从目前发病鸡群中分离的NDV毒株与La Sota弱毒株、标准F48E9强毒株间有很好的交叉免疫保护作用。     

新城疫分离株免疫保护试验

对经过鉴定的新城疫病毒穴NDV雪分离株,按国家兽医生物制品质量标准制备油乳剂灭活疫苗,在隔离器中接种SPF鸡,设标准LaSota疫苗株作对照,进行免疫保护实验。免疫后,每7d采血监测NDV抗体。免疫后3周,利用ND强毒分离毒和F48E9分别进行交叉攻毒实验,同时设SPF鸡对照。每天观察,及时剖检发病鸡,检察鸡群病变,以确定疫苗的保护性,以便对常规生产中的免疫失败进行原因分析。     

新城疫分离株免疫保护试验

对经过鉴定的新城疫病毒(NDV)分离株，按国家兽医生物制品质量标准制备油乳剂灭活疫苗，在隔离器中接种SPF鸡，设标准La Sota疫苗株作对照，进行免疫保护实验。免疫后，每7d采血监测NDV抗体。免疫后3周，利用ND强毒分离毒和F48E。分别进行交叉攻毒实验，同时设SPF鸡对照。每天观察，及时剖检发病鸡，检察鸡群病变，以确定疫苗的保护性，以便对常规生产中的免疫失败进行原因分析。     

如何防控强毒新城疫

2005年11月到2006年5月份,我市及周边县市养鸡户在已经接种H5亚型禽流感灭活疫苗的产蛋鸡群、育成鸡和未接种H5亚型油苗的肉鸡群、雏鸡群中,普遍发生了一种发病急、死亡快、死亡率3%到30%、后期出现神经症状的疫病,经山东农业大学动物医学院专家确诊为强毒新城疫(ND)。该病若与H9亚型禽流感并发感染,死亡率可达90%,与大肠杆菌、支原体混感时,死淘率可达40%。康复鸡群产蛋恢复相当缓慢,损失相当严重。根据哈尔滨兽医研究所曹殿军(2004年)研究证实,我国现在流行的NDV主要以基因Ⅶ型NDV为主,同时存在我国特有的基因Ⅸ型NDV感染,他对采自全国24个省市的91株NDV分析指出,基因Ⅶ型占51株,基因Ⅸ型占9株,基因Ⅵ型占15株,基因Ⅱ型占9株。如此严重的强毒NDV流行,再加上高致病性禽流感的消极影响,给我们养鸡业造成沉重打击。如何防控强毒ND已经成迫在眉睫的问题,笔者根据所掌握的资料及近年来防治ND方面取得的成功经验,加以总结,供同行参考。     

Newcastle disease virus outbreaks: Vaccine mismatch or inadequate application?

Newcastle disease (ND) is one of the most important diseases of poultry, and may cause devastating losses in the poultry industry worldwide. Its causative agent is Newcastle disease virus (NDV), also known as avian paramyxovirus type 1. Many countries maintain a stringent vaccination policy against ND, but there are indications that ND outbreaks can still occur despite intensive vaccination. It has been argued that this may be due to antigenic divergence between the vaccine strains and circulating field strains. Here we present the complete genome sequence of a highly virulent genotype VII virus (NL/93) obtained from vaccinated poultry during an outbreak of ND in the Netherlands in 1992-1993. Using this strain, we investigated whether the identified genetic evolution of NDV is accompanied by antigenic evolution. In this study we show that a live vaccine that is antigenically adapted to match the genotype VII NL/93 outbreak strain does not provide increased protection compared to a classic genotype II live vaccine. When challenged with the NL/93 strain, chickens vaccinated with a classic vaccine were completely protected against clinical disease and mortality and virus shedding was significantly reduced, even with a supposedly suboptimal vaccine dose. These results suggest that it is not antigenic variation but rather poor flock immunity due to inadequate vaccination practices that may be responsible for outbreaks and spreading of virulent NDV field strains.     

Advancement in vaccination against Newcastle disease: recombinant HVT NDV provides high clinical protection and reduces challenge virus shedding with the absence of vaccine reactions

Newcastle disease (ND) is a highly contagious disease of chickens causing significant economic losses worldwide. Due to the limitation in their efficacy, current vaccination strategies against ND need improvements. This study aimed to evaluate a new-generation ND vaccine for its efficacy in providing clinical protection and reducing virus shedding after challenge. Broiler chickens were vaccinated in ovo or subcutaneously at hatch with a turkey herpesvirus-based recombinant vaccine (rHVT) expressing a key protective antigen (F glycoprotein) of Newcastle disease virus (NDV). Groups of birds were challenged at 20, 27, and 40 days of age with a genotype V viscerotropic velogenic NDV strain. Protection was 57% and 81%, 100% and 95%, and 100% and 100% after the subsequent challenges in the in ovo and subcutaneously vaccinated chickens, respectively. Humoral immune response to vaccination could be detected from 3-4 wk of age. Challenge virus shedding was lower and gradually decreased over time in the vaccinated birds compared to the unvaccinated control chickens. In spite of the phylogenetic distance between the NDV F gene inserted into the vector vaccine and the challenge virus (genotype I and V, respectively), the rHVT NDV vaccine provided good clinical protection and significantly reduced challenge virus shedding.     

Generation of a genotype VII Newcastle disease virus vaccine candidate with high yield in embryonated chicken eggs

To generate a genotype VII Newcastle disease virus (NDV) vaccine with high yield in embryonated chicken eggs, we selected genotype VII NDV strain JS5/05, which possesses a high virus titer in embryos as the parental virus. Using reverse genetics, we generated a genetically tagged derivative (NDV/AI4) of JS5/05 by changing the amino acid sequence of the cleavage site of the F0 protein. Pathogenicity tests showed that NDV/AI4 was completely avirulent. NDV/AI4 was genetically stable and replicated efficiently during 10 consecutive passages in embryos. More importantly, serologic assays showed that oil-emulsion NDV/AI4 induced higher hemagglutination inhibition (HI) titers against the prevalent virus than oil-emulsion LaSota vaccine in chickens and geese. Moreover, NDV/AI4-induced HI titers rose faster than those elicited by LaSota in chickens. Both NDV/AI4 and LaSota provided protection against clinical disease and mortality after the challenge with the genotype VII NDV strain JS3/05. However, NDV/AI4 significantly reduced virus shedding from the vaccinated birds compared to LaSota. Taken together, these results suggest that NDV/AI4 can provide better protection than LaSota and is a promising vaccine candidate against genotype VII NDV.     

鸡新城疫病毒强毒株的分离鉴定及生物学特性研究

从黑龙江省某地发病鸡群中分离出一株病毒APMV1/chicken/China/HLJ-2/02,分离毒为速发型NDV强毒株,对经典NDV La Sota株免疫的雏鸡及高抗体母鸡仍有很强的致病力.本研究对分离株进行了生物学特性研究,并对部分基因进行了序列测定,序列已经发送Gene Bank,序列号为AY208695.采用NDV分离毒株制备成多价油乳剂灭活苗,免疫鸡群有良好的保护力.     

Protection of chickens from Newcastle disease with a recombinant baculovirus subunit vaccine expressing the fusion and hemagglutinin-neuraminidase proteins

Recombinant baculoviruses containing the fusion (F) and hemagglutinin-neuraminidase (HN) glycoprotein gene of the viscerotropic velogenic (vv) Newcastle disease virus (NDV) isolate, Kr-005/00, and a lentogenic La Sota strain of the NDV were constructed in an attempt to develop an effective subunit vaccine to the recent epizootic vvNDV. The level of protection was determined by evaluating the clinical signs, mortality, and virus shedding from the oropharynx and cloaca of chickens after a challenge with vvNDV Kr-005/00. The recombinant ND F (rND F) and recombinant HN (rND HN) glycoproteins derived from the velogenic strain provided good protection against the clinical signs and mortality, showing a 0.00 PI value and 100% protection after a booster immunization. On the other hand, the combined rND F + HN glycoprotein derived from the velogenic strain induced complete protection (0.00 PI value and 100% protection) and significantly reduced the amount of virus shedding even after a single immunization. The rND F and rND HN glycoproteins derived from the velogenic strain had a slightly, but not significantly, greater protective effect than the lentogenic strain. These results suggest that the combined rND F + HN glycoprotein derived from vvNDV can be an ideal subunit marker vaccine candidate in chickens in a future ND eradication program.     

Newcastle disease outbreaks in western China were caused by the genotypes VIIa and VIII

Twelve Newcastle disease virus (NDV) strains were isolated from chickens involved in outbreaks of Newcastle disease (ND) in western China (Shaanxi, Gansu, Xinjiang, Qinghai and Guangxi provinces) between 1979 and 1999. All strains were determined to be velogenic by plaque formation, the mean death time (MDT) of embryonated eggs, and the intracerebral pathogenicity index (ICPI). For preparation of virus RNA, the acid guanidinium-thiocyanate method was used. A 908bp fragment of nucleotide was amplified by RT-PCR starting from the N terminal of the F gene and the PCR segments were cloned into the PGEM-T vector and sequenced. The similarities of the nucleotide sequences (1-519bp) and predicted amino acid sequences of the F gene (1-125) were analyzed by comparing the 12 NDV isolates with the NDV vaccine strains Lasota, B1, H1 and V4, with classical NDV strains and recent epizootic strains. Phylogenetic analysis demonstrated that all strains were of two novel genotypes; the NDV strains that caused the outbreak of ND in western China during 1998-1999 was of the genotype VIIa, whereas the strains from the Qinghai province (1979-1985) were of genotype VIII, which has been found predominately in southern Africa.     

Protective efficacy of commercial Newcastle disease vaccines against challenge of goose origin virulent Newcastle disease virus in geese

Since 1997, severe outbreaks of Newcastle disease (ND) in geese in many regions throughout China have resulted in high morbidity and mortality, and great economic loss to farmers; however, no licensed, specific vaccine is yet available for this disease in China. In this study, goslings were immunized with different combinations and dosages of several commercial ND vaccines including La Sota vaccine, Mukteswar vaccine, recombinant live vaccine against avian influenza (AI) and ND (rL-H5 strain), and inactivated ND oil-emulsion vaccine (La Sota strain). The protective effects were evaluated based upon the level of antibody response and the degree of protection against the goose-origin virulent NDV strain. The result showed that two doses (i.e., one more than that for chicken) of La Sota vaccine priming, followed by 2-5 doses of Mukteswar vaccine boosting 2-3 weeks later, not only induced higher HI antibody levels, but also conferred longer-lasting protection. This immunization procedure can be recommended for prevention of ND in geese.     

鸽新城疫的流行与防控

鸽新城疫是由新城疫病毒感染鸽群引起的传染病, 在世界各国鸽场均有流行。介绍了鸽新城疫流行情况及特点, 流行毒株的基因型、病毒的毒力、病毒的抗原特性, 提出在做好鸽场内生物安全控制和精细化管理基础上, 使用市售新城疫疫苗进行合理免疫是鸽新城疫防控的关键。     

Molecular characterization of Newcastle disease viruses isolated from rural chicken in northwest Ethiopia reveals the circulation of three distinct genotypes in the country

Newcastle disease (ND) is a highly contagious disease that affects many species of birds and causes significant economic losses to the poultry industry worldwide. Fifteen Newcastle disease virus (NDV) isolates obtained from rural chickens in northwest Ethiopia in 2011 and 2012 were characterized genotypically. The main functional region of the F gene was amplified and sequenced (260 nucleotides). Among the Ethiopian NDV isolates, 2 isolates had the virulent motif ¹¹²R-R-Q-K-R-F¹¹⁷ at the cleavage site of the fusion protein while 13 isolates contained the lentogenic motif ¹¹²G-G/R-Q-G-R-L¹¹⁷. Phylogenetic analysis based on the variable region of the F gene indicated that the two isolates exhibiting the virulent motif belonged to lineage 5 (genotype VII) subgenotype d and the remaining 13 isolates were grouped into lineage 2 (genotype II). The nucleotide sequences of lineage 5 isolates were genetically related to the Sudanese NDV isolates, suggesting potential epidemiological link of ND outbreaks between neighbouring countries. The lentogenic strains shared similarities with La Sota vaccine strain and probably originated from the vaccine strain either through direct exposure of birds to the live vaccine or to infectious La Sota-like strains circulating in rural poultry. This study provides genetic evidence on the existence of different NDV genotypes circulating in the rural poultry in Ethiopia. The virulent NDV continues to be a problem in poultry sector in Ethiopia, and their continuous circulation in rural and commercial poultry calls for improved surveillance and intensified vaccination and other control measures.