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禽流感(avian influenza,AI)是由A型流感病毒引起的家禽或野禽的疾病综合征。根据禽流感病毒(AIV)的致病力通常分为高致病性禽流感(HPAI)和低致病性禽流感(MPAI),HPAI传播快,具有高度致死性;MPAI多呈隐性感染或症状较轻,不导致严重病变或死亡。AI历来被认为是人类流感的最大基因库,是人流感病毒发生变异的新基因来源。1997年,中国香港H5N1 AIV及1999年中国大陆和香港H9N2AIV首次突破种间障碍直接感染人甚至致死。不但打破了自然条件下仅有H1、H2和H3亚型流感病毒可以感染人和其他哺乳动物的常规,而且为人流感增添了新的毒株亚型(H5和H9)。由此赋予了AIV(禽流感病毒)全新的公共卫生意义。 相似文献
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禽流感病毒致病性的分子基础和公共卫生意义 总被引:2,自引:0,他引:2
禽流感(AI)是由正粘病毒科、流感病毒属A型流感病毒引起的禽类疾病综合征。禽流感病毒(AIV)广泛存在于多种家禽和野生禽类中,AIV低致病力毒株可引起禽类的轻度呼吸系统疾病,高致病力毒株引起禽类的急性致死性疾病,可引起禽类高达100%的死亡。由于AIV抗原性和致病力的易变性及其血清型毒株间缺乏交叉保护性,使AI已成为世界各国养禽业面临的重要问题并给养禽业造成了很大的经济损失。虽然AIV通常仅感染家禽,但AIV也被认为是人流感病毒发生变异的新基因来源,1997年香港H5N1 AIV和2003年2月荷兰H7N7 AIV致人死亡的事件,以及今年在亚洲广泛流行并在越南、泰国等导致数十人死于与HPAI(H5N1)感染相关的疾病等,这些撼人事件引起各国政府和全世界学者的广泛关注,从而使AIV具有了全新的公共卫生意义,人们应该对禽流感病毒的结构及致病性的分于基础和公共卫生意义给予高度重视。 相似文献
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禽流感(AI)是由A型流感病毒引起的发生于各种家禽和野鸟的高度接触性传染病,此病毒有多种血清亚型,其中大部分是没有致病性的,有些是属于低致病性的。根据禽流感病毒致病性和毒力的不同,可以将禽流感分为高致病性禽流感、低致病性禽流感和非致病性禽流感。其中,高致病性禽流感已被世界动物卫生组织列为A类传染病。1病原禽流感的病原为禽流感病毒(AIV),该病毒属正粘病毒科,正粘病毒属,A型流感病毒。AIV除A型外,还有B型、C型。其中B、C两型仅见于人类,而A型对人类和动物都能感染。在AIV表面有两种重要的表面抗原,即血细胞凝集素(HA)… 相似文献
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H9N2亚型禽流感病毒流行病学及其疫苗的研究进展 总被引:1,自引:0,他引:1
《中国兽医学报》2017,(2):386-392
禽流感(avian influenza AI)是由A型流感病毒引起的一种高度接触性传染病。H9N2是A型流感病毒的1个亚型,其谱系复杂,流行范围广,已经成为我国AI的主要亚型。尽管我国自1998年就开始进行H9N2亚型禽流感病毒(AIV)的防疫,但目前其疫苗株与流行株的抗原性已经出现了较大的差异。带毒野禽的迁徙不仅使H9N2AIV防控难度加大,而且使AI的流行不断复杂化;活禽交易市场为AIV重排以及跨种传播提供了有利的条件。此外,H9N2AIV感染谱在不断扩大,不仅感染哺乳动物,甚至已经感染了人群;因此,有必要重新认识H9N2AIV的兽医学和公共卫生学意义。现就H9N2AIV近年在我国的流行情况及其疫苗的研究进展作一综述。 相似文献
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禽流感的诊断与防制 总被引:1,自引:0,他引:1
禽流感(avianinfluenza,AI),俗称为真性鸡瘟或欧洲鸡瘟,是由A型呷型)流感病毒(AIV)引起的家禽或野禽的一种感染或疾病综合症。自从1878年Perroncito首次描述AI至今,人类已从家禽或野禽中分离到许多不同AIV毒株,这些毒株对于同品种的家禽或野禽来说,其表现的毒力有很大差异;即使同一AIV毒株,对于不同的禽类,也可能表现不同的毒力。因此,在临诊上,AI可引起禽类出现无症状的亚临诊感染至几乎100%的急性死亡不等。每次流感,尤其是高致病性禽流感(HPAI)的发生与流行,不但造成家禽(尤其是火鸡和鸡)出现大批死亡,… 相似文献
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禽流感(AI)是由禽流感病毒(AIV)引起的一种高度接触性传染病,主要感染家禽和野禽,1966年首次分离得到H9N2。H9N2是AIV的一个亚型,经过长达数十年的遗传变异,已成为当前流行的禽流感病毒主要亚型之一。除了感染鸡、鸭等禽类,H9N2亚型AIV还可感染猪、水貂等哺乳类动物,甚至还可以感染人。虽然H9N2亚型AIV是低致病性的,但它能与其他病毒或细菌引起共感染,还能与其他亚型流感病毒进行重排,形成新型重组病毒,对公共卫生安全造成了不容忽视的潜在危害。文章就H9N2亚型AIV的遗传变异、重组、致病力和跨种传播等方面进行了简要论述。 相似文献
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禽流感(Avian Influenza.AI)是由A型流感病毒(Avian Influenza Virus.AIV)引起的一种高度接触性传染病.鸡、火鸡、鸭等家禽及野鸟均可感染.由于AIV负链、分节段的RNA病毒性质,病毒很容易发生变异并不断的突破其感染宿主的种属障碍,引起新的流感流行.AIV据其致病性可分为高致病性AIV(Highly Pathogenic Avian Influenza virus,HPAIV)和低致病性AIV(Low Pathogenic Avian In-fluenza virus,LPAIV),感染家禽的HPAIV和LPAIV分别以H5和H9亚型为主. 相似文献
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魏静 《四川畜牧兽医学院学报》2009,(4):28-32
在现代法律秩序中,商会自治规范是制定法的基础和必要的补充,甚至在某些方面替代了制定法;商会自治规范主要包括商会组织规范、行为规范、惩罚规范以及争端解决规范等;其效力仅及于其内部成员;商会自治规范和制定法之间存在冲突,但也存在整合的基础。 相似文献
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本文概述了猪的毛色类型、猪的毛色遗传模式,着重综述了猪毛色基因分子基础的研究进展,指出存在问题并就未来发展方向做了思考。 相似文献
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REASONS FOR PERFORMING STUDY: Centesis of the bicipital bursa using an 8.9 cm long spinal needle has been reported but the alternative of employing a 3.8 cm long hypodermic needle requires validation. OBJECTIVE: To compare the efficacy of 2 different methods of centesis of the bicipital bursa and to evaluate the usefulness of ultrasonographic imaging to determine the location of solution administered when centesis of the bursa is attempted. METHODS: For Trial 1, 6 clinicians, who had no previous experience of centesis of the bicipital bursa, attempted to inject a solution composed of an aqueous radiopaque contrast medium and physiological saline solution (PSS) into the bicipital bursae of 2/12 horses using the previously described distal approach to inject one bursa and a proximal approach to inject the contralateral bursa. The bicipital tendon and bursa were examined ultrasonographically before and after injection; and both shoulders were examined radiographically to identify the location of the medium. In Trial 2, another 6 clinicians, also with no previous experience of centesis, repeated Trial 1, using 6 horses, but the radiopaque contrast medium was mixed with air instead of PSS. RESULTS: Accuracy of centesis using the proximal approach was 39% and that of the distal approach 28%. Ultrasonographic examination of the shoulder allowed the location of solution and air to be accurately predicted in all 12 shoulders examined. CONCLUSIONS: Clinicians who have had no previous experience performing centesis of the bicipital bursa are unlikely to be successful in centesis using either approach. Radiographic examination after injecting a radiopaque contrast medium may be necessary to assess the success of centesis especially if bursal fluid is not obtained during centesis. Injecting air along with the radiopaque contrast medium provides more accurate ultrasonographic confirmation of centesis and better radiographic definition than does injection without air. 相似文献
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Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF
Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo. 相似文献
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乳酸杆菌作为益生菌广泛用于人和动物.本文综述了乳酸杆菌改善宿主健康的机制.乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道.文章重点讨论了乳酸杆菌表面成分(表面蛋白、脂磷壁酸和肽聚糖)与肠道受体(C型凝集素受体、Toll样受体和Nod样受体),阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制. 相似文献