| 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. |
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