两种组胺受体拮抗剂对高致病性猪蓝耳病临床症状的影响

为了解组胺H1、H2受体拮抗剂对高致病性猪蓝耳病临床症状的影响,探讨内源性组胺在患病仔猪发热、呼吸困难、耳尖发绀等典型临床症状中的作用机理.选择20头30日龄的公仔猪,通过人工感染使仔猪患高致病性猪蓝耳病,并随机分为扑尔敏组、西咪替丁组、阳性组、阴性组.每日测量仔猪直肠体温,称量仔猪日采食量,观察仔猪的临床症状变化情况...     

鸡低致病性禽流感防治研究

禽流感是家畜最常见的传染性病毒,主要是由于A型禽流感病毒引发的,它的重要侵害对象是禽类,禽流感按其性质可以分为高致病性禽流感、低致病性禽流感和无致病性禽流感,日常生活中最常见的禽流感是低致病性禽流感.为更好研究出防治低致病性禽流感措施,本文简单说明了和分析了低致病性禽流感的含义和它的流行特点.     

两种组胺受体拮抗剂对内毒素诱导雏鸡肺损伤的影响

为探讨2种组胺受体拮抗剂在内毒素诱导肺损伤中的作用机理,作者设计了本试验。将120羽20日龄雏鸡随机分为5组,每组24羽。内毒素诱导肺损伤模型组每天早晚注射生理盐水0.5 mL.只^-1,中午腹腔注射内毒素100μg.kg^-1;扑尔敏组每天早晚肌注扑尔敏0.5 mL.只^-1,中午腹腔注射内毒素100μg.kg^-1;西咪替丁组每天早晚肌注西咪替丁0.5 mL.只^-1,中午腹腔注射内毒素100μg.kg^-1;扑西联合组每天早晚肌注西咪替丁、扑尔敏各0.3 mL.只^-1,中午腹腔注射内毒素100μg.kg^-1;空白组每天早中晚注射同等剂量生理盐水,连续15d。在第5、10、15天,各组随机抽7个样本,颈动脉放血处死,称取肺质量,采集肺脏以荧光法测组胺含量,制备病理切片观察病理变化并评分。结果发现：（1）第5天,扑西联合组肺组织中组胺含量显著低于扑尔敏组和西咪替丁组（P〈0.05）。在第10天时,模型组肺组织中组胺含量显著高于扑西联合组和空白组（P〈0.05）;在第15天时,模型组肺组织中组胺含量显著（P〈0.05）高于扑尔敏组和空白组,极显著（P〈0.01）高于扑西联合组;（2）第10天时,扑尔敏组和空白组肺指数显著（P〈0.05）或极显著（P〈0.01）低于模型组,第15天时,扑尔敏组、扑西联合组和空白组肺指数显著（P〈0.05）低于模型组;（3）第5、10、15天时,模型组肺病理评分分值与其余各试验组差异极显著（P〈0.01）,在第5天时,扑西联合组极显著低于扑尔敏组和西咪替丁组（P〈0.01）,在第10、15天时,扑西联合组显著低于（P〈0.05）扑尔敏组,极显著低于其它各组（P〈0.01）。结果表明,组胺通过H1、H2受体参与介导内毒素诱导雏鸡肺的损伤,但H1受体起主导作用。     

长寿地区低致病性禽流感防控要点

低致病性禽流感直接间接给养殖户带来巨大损失,作者通过流行特点、临床症状、解剖症状及病理变化、诊断和防控5个方面具体讲解低致病性禽流感的防控。     

低致病性禽流感病毒对养禽业的危害

文章对致病性禽流感病毒的特性、对养禽业的危害以及致病性禽流感的预防作了综合性叙述,重点对低致病性禽流感病毒的危害、免疫抑制性、毒性的变异性作了叙述,对生产、科研具有一定的参考意义。     

低致病性禽流感的防制措施

近年来,世界范围内高致病性禽流感疫情已大大减少,而低致病性禽流感疫情时有发生。低致病性禽流感又叫致病性禽流感、非高致病性禽流感和温和型禽流感,是指某些致病性低的禽流感病毒毒株(如H9N2亚型)感染家禽引起的以低死亡率和轻度     

低致病性禽流感对鸡抗体水平的影响及防治

1低致病性禽流感对鸡生产及抗病性能的影响 蛋鸡在刚开产阶段和180~240日龄易发生低致病性禽流感。对蛋鸡来说从不产蛋到开始产蛋也是很大的生理性应激,抵抗力较低的鸡只容易感染。产蛋高峰时蛋鸡较多,也是易发的原因。蛋鸡产蛋率下降明显,没有注射疫苗的蛋鸡产蛋下降幅度为30%,甚至更高,注射疫苗的鸡群产蛋下降幅度较小,产蛋下降幅度的高低和免疫抗体情况有关。本病无继发感染,一般无鸡只死亡。     

两种组胺受体拮抗剂治疗奶牛蹄叶炎效果观察

为了解组胺H1、H2受体拮抗剂在奶牛临床型蹄叶炎治疗方面的效果,探索内源性组胺与牛蹄角质软化、疼痛和跛行等典型临床症状的相互关系,本试验选择4～7岁的病牛33头,随机分为盐酸苯海拉明组、雷尼替丁组和对照组,在不改变其他任何条件的前提下,两个试验组分别在饲料中添加盐酸苯海拉明、雷尼替丁等组胺H1、H2受体拮抗剂进行为期9个月的试验。结果表明,组胺受体拮抗剂能够缓解奶牛蹄叶炎临床症状,显著缩短患牛病程;使用盐酸苯海拉明治疗组,病程由平均238d缩短为147d(P<0.01);使用雷尼替丁治疗组,病程由平均238d缩短为191d(P<0.01);H1受体拮抗剂较H2受体拮抗剂对于缓解临床症状效果明显。临床型蹄叶炎患病奶牛较蹄部无临床症状奶牛血清组胺含量明显增高。组胺受体拮抗剂使用后不影响牛奶品质。     

低致病性禽流感及其预防措施

近年来,由于H5N1型高致病性禽流感对我国养殖业造成了严重损失,人们对高致病性禽流感的防控给予了高度重视,H5N1亚型疫苗政府免费发放,并实行强制免疫.这些措施使养殖户强化了对高致病性禽流感的防制工作,但形成认识上的误区,认为低致病性禽流感H9N2亚型的免疫不重要,不少人放松了对低致病性禽流感的防控工作.一些大规模蛋鸡养殖场低致病性禽流感H9N2亚型或非典型性新城疫的发生,已成为困扰蛋鸡行业健康发展的主要障碍.因此,加强低致病性禽流感的防控工作同样值得人们关注.     

美国发现低致病性禽流感病毒

美国农业部和内政部2006年8月14日联合宣布，正在进行的野生鸟类禽流感病毒监测发现，密歇根州的两只野生天鹅携带禽流感病毒，但不是在亚洲、欧洲和非洲流行的高致病性HsN1亚型，因此，不对人类构成威胁。     

Effect of a prior exposure to a low pathogenic avian influenza virus in the outcome of a heterosubtypic low pathogenic avian influenza infection in mallards (Anas platyrhynchos)

Wild birds, particularly Anseriformes and Charadriiformes, are considered the natural reservoir of low pathogenic avian influenza (LPAI) viruses. The high prevalence and subtype diversity of avian influenza viruses at premigrational staging areas provide the perfect opportunity for multiple exposures to different LPAI virus subtypes. Natural consecutive and concurrent infections of sentinel ducks with different LPAI virus subtypes have been reported. The protective immune response from different LPAI virus infections is not understood nor is the effect of such repeated exposures. This study experimentally evaluated the effect of a prior exposure to a LPAI virus on the outcome of a heterosubtypic LPAI virus infection in mallards (Anas platyrhynchos). The results of this investigation suggest that recent prior exposure to a LPAI virus may affect the outcome of a subsequent heterosubtypic LPAI infection in mallards by reducing the duration of cloacal and oropharyngeal viral shedding as well as the viral load excreted via the cloaca. Wild mallards are likely exposed to multiple subtypes of LPAI virus during the periods of peak viral circulation, and the results of this study suggest that the duration of viral shedding in subsequent exposures might be reduced.     

2009—2010年华东地区家禽低致病性禽流感病毒的流行病学调查与分析

为了解华东地区家禽中低致病性禽流感病毒（low pathogenic avian influenza viruses,LPAIVs）的分布规律,从2009年10月到2010年9月在华东地区某活禽市场采集鸡、鸭、鹅等家禽的泄殖腔拭子共1 650份,经鸡胚接种和HA、HI试验鉴定,结果从58份样品中分离到了LPAIVs,总分离率为3.51%。所分离到的6种HA亚型及各HA亚型分离率从高到底依次为：H6、H3、H1、H4、H9、H11。从这些样品中鉴定出7种NA亚型,包括N1、N2、N3、N4、N5、N6、N8,二者之间有11种组合。家鸭样品中LPAIVs的分离率为7.28%,显著高于鸡源样品的分离率1.00%和鹅源样品的分离率1.02%。LPAIVs的季节性分布较为明显,3～6月份和10～12月份的分离率较高,而冬季最冷的1月份和夏季最热的7月份则没有分离到。2种或2种以上不同HA亚型混合感染的样品有6份,全部为水禽源样品,占总阳性样品数的10.34%。这些数据表明活禽市场可以作为AIV的一个重要储存库,而家养水禽可作为AIV的一个重要储存宿主,应该继续加强对活禽市场,尤其是家养水禽中AIV的监测。     

高致病性禽流感的控制措施

日本、韩国、越南和泰国等国家相继发生了高致病性禽流感,不仅给这些国家的养禽业带来巨大经济损失,而且还出现了人感染禽流感死亡的情况,严重地威胁了人类的健康。我国广西、上海、广东等十几个     

Risk based surveillance for early detection of low pathogenic avian influenza outbreaks in layer chickens

Current knowledge does not allow the prediction of when low pathogenic avian influenza virus (LPAIV) of the H5 and H7 subtypes infecting poultry will mutate to their highly pathogenic phenotype (HPAIV). This mutation may already take place in the first infected flock; hence early detection of LPAIV outbreaks will reduce the likelihood of pathogenicity mutations and large epidemics. The objective of this study was the development of a model for the design and evaluation of serological-surveillance programmes, with a particular focus on early detection of LPAIV infections in layer chicken flocks. Early detection is defined as the detection of an infected flock before it infects on average more than one other flock (between-flock reproduction ratio R_f < 1), hence a LPAI introduction will be detected when only one or a few other flocks are infected. We used a mathematical model that investigates the required sample size and sampling frequency for early detection by taking into account the LPAIV within- and between-flock infection dynamics as well as the diagnostic performance of the serological test used. Since layer flocks are the target of the surveillance, we also explored whether the use of eggs, is a good alternative to sera, as sample commodity. The model was used to refine the current Dutch serological-surveillance programme. LPAIV transmission-risk maps were constructed and used to target a risk-based surveillance strategy. In conclusion, we present a model that can be used to explore different sampling strategies, which combined with a cost-benefit analysis would enhance surveillance programmes for low pathogenic avian influenza.     

Quantitative transmission characteristics of different H5 low pathogenic avian influenza viruses in Muscovy ducks

EU annual serosurveillance programs show that domestic duck flocks have the highest seroprevalence of H5 antibodies, demonstrating the circulation of notifiable avian influenza virus (AIV) according to OIE, likely low pathogenic (LP). Therefore, transmission characteristics of LPAIV within these flocks can help to understand virus circulation and possible risk of propagation. This study aimed at estimating transmission parameters of four H5 LPAIV (three field strains from French poultry and decoy ducks, and one clonal reverse-genetics strain derived from one of the former), using a SIR model to analyze data from experimental infections in SPF Muscovy ducks. The design was set up to accommodate rearing on wood shavings with a low density of 1.6 ducks/m²: 10 inoculated ducks were housed together with 15 contact-exposed ducks. Infection was monitored by RNA detection on oropharyngeal and cloacal swabs using real-time RT-PCR with a cutoff corresponding to 2–7 EID50. Depending on the strain, the basic reproduction number (R₀) varied from 5.5 to 42.7, confirming LPAIV could easily be transmitted to susceptible Muscovy ducks. The lowest R₀ estimate was obtained for a H5N3 field strain, due to lower values of transmission rate and duration of infectious period, whereas reverse-genetics derived H5N1 strain had the highest R₀. Frequency and intensity of clinical signs were also variable between strains, but apparently not associated with longer infectious periods. Further comparisons of quantitative transmission parameters may help to identify relevant viral genetic markers for early detection of potentially more virulent strains during surveillance of LPAIV.