【作者】 施国锋；

【导师】 陈安国；

【作者基本信息】 浙江大学 ， 农业推广， 2005， 硕士

【摘要】 猪繁殖与呼吸综合症(PRRS)自1987年首次在美国发现至今,已经成为全世界养猪业上传播最广、损失最大的传染病之一。它不仅在爆发时造成大量怀孕后期母猪的流产,同时还使哺乳仔猪和保育仔猪发生严重的呼吸系统疾病而大批死亡。危害更大的是,在PRRS爆发过后,猪只的免疫系统受到了抑制,使其它病原体容易侵入机体而引起继发性感染。如支原体肺炎、胸膜肺炎、猪副嗜血杆菌及其它病毒性疾病。而且大多数猪场在PRRS爆发过后,出现的都是几种细菌或病毒的混合感染。由于病猪表现出的症状不一,所以在临床上用药也比较困难。因此,猪场的药费支出大幅度上升,但死亡率却居高不下。有些猪场的死亡率高达30%,严重地影响了猪场的经济效益。很多猪场病急乱投医,胡乱地使用PRRS疫苗。而且有些疫苗质量还不稳定,特别是弱毒苗,结果使PRRS的情况更加复杂。 由于PRRS给世界的养猪业造成了具大的损失,所以各国的专家和学者对PRRS的发病机理和控制方法作了大量的研究。特别是美国的一些科研机构,在对PRRSV的感染途径、排毒的持续时间等方面作了更为详细的研究。为猪场控制和清除PRRSV提供了的理论和实践上的依据。清除PRRS最简单、彻底的方法是全场清群—再建群。但这种方法代价太高。除此之外,还有部分清群法、隔离早期断奶、检测和移走、猪只单向流动结合大剂量的疫苗注射、群体封闭五种方法。通过这五种方法来控制和清除PRRSV,最后都需要PRRS阴性的后备种猪来更新感染过PRRSV的阳性母猪。但是目前我国大多数种猪场已感染了PRRSV,如何用PRRS阳性的种猪生产出PRRS阴性猪,是目前我国养猪业所要考虑的问题。本文通过新猪场用PRRS阳性的种猪群生产出PRRS阴性猪、PRRS阳性的老猪场用隔离断奶的方法生产出PRRS阴性猪、PRRS阳性的老猪场用部分清群法清除PRRSV三个试验,来对这个问题进行了详细的描述。 第一个试验,试验猪共有28头公猪,506头母猪,经ELISA测定,送检的样本全部为PRRS阳性。于2002年11月12日起至11月30日分五批运入一个新建成的三点式布局的猪场。通过执行严格的生物安全制度和生产管理规程,于2003年5月初开始产仔。至2003年7月底,在第一批已达70日龄以上的生长猪中随机抽取30头的血液样本,进行PRRS抗体的ELISA测定,结果全部为阴性。在2004年3月25日又抽取10头育肥猪、10头保育猪、10头母猪和2头公猪的血液进行PRRS抗体的ELISA测定,结果母猪和公猪基本维持阳性,但保育猪和育肥猪全部阴性。而且一年中的生产水平令人满意。说明只要计划周密、操作准确,在新猪场是完全可以用PRRS阳性种猪生产出PRRS阴性的后代,而且不需要额外的投入,生产水平也令人满意。 第二个试验,试验猪共有266头,来自同一个PRRS阳性猪场,日龄在12-18天的早期断奶仔猪。进入一个事先挑选好的、隔离条件较好的临时养猪的场地,并且已经作好了消毒和保温工作。在整个试更多还原

【Abstract】 Porcine Reproductive and Respiratory Syndrome (PRRS) has been one of the most wide spread and economic cost of swine disease in the world since it has been found first time in US. It not only cause high percentage of late gestation sow abortion when out break of PRRS, but also cause high mortality in suckling piglets and nursery pigs by respiratory problem. More seventy, after out break of PRRS, the immune system of pig has been restrain. It makes easier to another pathogens to invade into the body and caused secondary infection. Such as Mycoplasma Pneumonia, Actinobacillus pleuropneumoniae, Haemophilus parasuis and other virus diseases. Most of pig farms show the complex disease symptom that infected by several bacteria and virus combination. Because of different pathogens, it is difficult to antibiotic to control. That makes pig farm cost increase for buying antibiotic, but the mortality is still very high. Some farm’s mortality are high than 30%, that is heavily affect the farm efficiency. Many farm start to use PRRS vaccine to control the disease. But the protection of PRRS vaccine is limited right now, some are even not qualified. Especially is live vaccine. That will make farm situation of PRRS much more complicated.PRRS caused big lost to the swine business in the world. Therefore, scientists in many countries have done a lot of researches to understand the disease mechanism and the way of control. Especially in USA, they have done some researches in detail of how the PRRSV infect pigs and how long the pigs will shed the virus. That gives the guild line to the farm in PRRS control and eradication. The most simple and easy way of PRRS eradication is farm depopulation and repopulation, but cost a lot. There are another 5 methods can be used in PRRS eradication. A. Partial depopulation, Segregated early wean, Test and removal, Mass vaccination with unidirectional pigflow, Herd closure. But all of these methods for PRRS control and eradication need PRRS negative gilts to replace the PRRS positive sows. Unfortunately, most of breeding farm in China right now have infected the PRRSV. How to use the PRRS positive breeding stocks to produce PRRS negative pigs? This study has answer the question in detail through three trials, which are "New farm use PRRS sero-positive breeding stock to produce PRRS sero-negative pigs", " Old PRRS sero-positive farm use segregated early wean to produce PRRS sero-negative pigs" and "PRRS sero-positive farm usepartial-depopulate to eradicate the PRRSV".In the first trial, we have used 28 boars and 506 girls that are all PRRS sero-positive which sampling tested by ELISA. They have been delivered into a new pig farm which is 3 sites layout started Nov 12, 2002 to Nov 30, 2002. after carry on strict bio-security regulation and production management discipline, gilts started farrowing on early May,.2003. Until end of Jul. 2003, we took 30 blood samples from the first group of grower who over 70 days old for ELISA test. The results are all PRRS sero-negative. On Mar.25, 2004, we took 10 finishers, 10 nursary pigs, lOsows and 2 boars of blood samples for PRRS test again by ELISA. The results are: finishers and nursry pigs are all sero-negative, sows and boars are still sero-positive mainly. Also, the performance of production is quite acceptable according to the first year production records. That means new farm can use PRRS sero-positive gilts to produce sero-negative offspring if farm has detail plan and accuracy operation. In another hand, it needs not capital input but has good performance.In second trial, we used 266 early weaned piglets that came from PRRS sero-positive farm and wean age about 12-18 days. They have moved to a well isolated place which we have selected prior after wean immediately. The room for piglets was disinfected and warmed up. One people were pointed to take the responsibility in feeding and management. He has to follow up the strict feeding management and bio-security regulation. After 75days trail, on Jul 31, 2003, we took 65 blood samples for PRRS ELISA test. All samples are sero-negative. This trial is another proof for first trial, also benefit to the PRRS positive farm who want to produce own PRRS negative replacement. The third trial was processing in a breeding farm that has good isolated location and 3 sites layout. The farm have 1000 plus sows and health status is very good since farm set up. So the production performance is excellent. Unfortunately, it has out broken the PRRS on Aug, 2002. After half year late, PRRS got stable and no clinical symptom could be found in the sow herd. 30 boars and sows blood samples were test for PRRS by ELISA. The result are all sero-positive. In order to reduce the impact of future production, half year of replacement has been selected. After the building for isowean piglets has been choose in the well isolated location, farm started isowean. All weaner moved to isowean building. 4 weeks late, only 3 weeks inventory was left in nursery. To empty the nursery barn, all nursery pigs have been moved to grower barn. Then nursary barns have been cleaned and disinfected. When first group of isowean pigs achieved 70 days old, 20% of pigs have been blood tested for PRRS by ELISA. The result was all sero-negative. That means isowean pigs has no PRRSV circulation. So that 3 weeks old of weaner have been moved into nursery on Jul,2003. At the same time,grower/finisher barn started cleaning and disinfection. Before grower/finisher barns repopulation, the first group of nursery has been tested for PRRS by ELISA. The result of 10 samples were all sero-negative. Thus, pigs are safety to be moved from nursery to grower/finisher barn. To follow up the progress, nursery and grower have been tested ELISA for 6 times in following 3 months and results were all PRRS sero-negative. The trial achieved the target what we expected. Of caused, the breeding farm also finished the PRRS eradication successfully.更多还原