猪繁殖与呼吸综合征的血清学调查

猪繁殖与呼吸综合征 ( PRRS)又称蓝耳病或神秘病 ,是近年来国际上最引人注目的一种新猪病 ,病原为猪繁殖呼吸综合征病毒 ( PRRSV)。本病于1 987年最早在美国暴发 ,1 990年冬传入欧洲 ,并很快在欧洲各国暴发和流行 ,现在 PRRS已在全世界范围内流行。中国最早于 1 996年检测猪群血清抗体阳性 ,并从可疑病猪群中分离了 PRRS病毒之后 ,有不少省市相继报道了该病 ,但福建省未见报道。PRRS不仅引起呼吸道感染、仔猪死亡、母猪繁殖障碍等直接损失 ,还会导致免疫抑制而继发多种其它疾病 ,给养猪业带来巨大的经济损失。 1 998年下半年以来 ,…     

猪繁殖和呼吸综合征油乳剂灭活苗的研制

使用猪场自行分离的PRRSV,进行细胞转瓶培养,收获病毒液后灭活,乳化制成油乳苗,各项指标检测均合格,并且免疫试验效果较好.     

Genetic analysis of reproductive performance in sows during porcine reproductive and respiratory syndrome(PRRS) and porcine epidemic diarrhea(PED)outbreaks

Background: Porcine reproductive and respiratory syndrome(PRRS) is one of the most infectious swine diseases in the world, resulting in over 600 million dollars of economic loss in the USA alone. More recently, the USA swine industry has been having additional major economic losses due to the spread of porcine epidemic diarrhea(PED).However, information regarding the amount of genetic variation for response to diseases in reproductive sows is still very limited. The objectives of this study were to identify periods of infection with of PRRS virus(PRRSV) and/or PED virus(PEDV), and to estimate the impact their impact on the phenotypic and genetic reproductive performance of commercial sows.Results: Disease(PRRS or PED) was significant(P 0.05) for all traits analyzed except for total piglets born.Heritability estimates for traits during Clean(without any disease), PRRS, and PED ranged from 0.01(number of mummies; Clean and PED) to 0.41(abortion; PED). Genetic correlations between traits within disease statuses ranged from-0.99(proportion born dead with number weaned; PRRS) to 0.99(number born dead with born alive;Clean). Within trait, between disease statuses, estimates ranged from-0.17(number weaned between PRRS and PED) to 0.99(abortion between Clean and PRRS).Conclusion: Results indicate that selection for improved performance during PRRS and PED in commercial sows is possible and would not negatively impact performance in Clean environments.     

猪繁殖与呼吸综合征病毒变异株与猪瘟病毒等混合感染的调查与分析

从华南地区PRRSV变异株(NSP21 594-1 680 bp缺失)核酸阳性的23个规模场、42个个体养殖场和15个散养户,随机采集发病、同群猪血清197份、组织样品115份,调查猪群个体感染PRRSV变异株情况,并对PRRSV变异株核酸阳性样品进行CSFV、PRV、PCV2、SIV检测,调查PRRSV变异株混合感染情况.结果表明:312份样品中224份PRRSV变异株核酸阳性,阳性率71.79%;PRRSV变异株核酸阳性样品中CSFV、PRV、PCV2核酸阳性样品分别为12份、2份,35份,阳性率分别为5.35%、0.89%、15.6%;80个场(群)均未检测到SIV核酸的存在.25个场(群)存在病毒混合感染,其中PRRSV变异株/CSFV、PRRSV变异株/PRV、PRRSV变异株/PCV2二重感染和PRRSV变异株/CSFV/PCV2、PRRSV变异株/PRV/PCV2三重感染猪场(群)百分率分别为5%、1.25%、21.25%和2.5%、1.25%.PRRSV变异株(NSP21594-1680变异)是造成猪场(群)重大损失的直接原因,并可与CSFV、PRV、PCV2等病毒出现混合感染,与PCV2混合感染比率较高.     

Genetic analysis of ORF5 of recent Korean porcine reproductive and respiratory syndrome viruses (PRRSVs) in viremic sera collected from MLV-vaccinating or non-vaccinating farms

The 23 open reading frame (ORF) 5 sequences of Korean type II porcine reproductive and respiratory syndrome virus (PRRSV) were collected from viremic sera from the (modified live vaccine) MLV-vaccinating and non-vaccinating farms from 2007 to 2008. The samples were phylogenetically analyzed with previous ORF5 sequences, including type I Korean PRRSV, and previously reported or collected sequences from 1997 to 2008. A MN184-like subgroup of type II Korean PRRSV was newly identified in the viremic sera collected from 2007 to 2008. And of the type I PRRSVs, one subgroup had 87.2~88.9% similarity with the Lelystad virus, showing a close relationship with the 27~2003 strain of Spain. The maximum parsimony tree of type II PRRSV from 1997 to 2008 showed that they had evolved to four lineages, subgroups 1, 2, 3 and 4. Most of the recently collected type II PRRSVs belonged to subgroup 4 (48%). The region of three B-cell epitopes and two T-cell epitopes of ORF5 amino acids sequences was considerably different from the MLV in subgroups 3 and 4. In conclusion, the existence of type I PRRSV, which was genetically different from Lelystad virus (Prototype of type I PRRSV), and heterologous type II PRRSVs of viremic pigs detected even in the MLV-vaccinating farms indicated the need for new vaccine approaches for the control of PRRSV in Korea.     

Risk factors for infection of sow herds with porcine reproductive and respiratory syndrome (PRRS) virus

In 1992, the porcine reproductive and respiratory syndrome virus (PRRSV) of European type (PRRSV-EU) was introduced in Denmark. By 1996, the virus had spread to approximately 25% of the Danish herds. In January 1996, a modified-live vaccine based on the American type of the virus (PRRSV-US) was used in replacement boars for Danish artificial insemination (AI) centres and from July 1996, the vaccine was used in PRRSV-EU infected herds for prevention of disease. Soon after vaccine introduction, PRRSV non-infected herds experienced outbreaks of disease due to infection with PRRSV-US. In this study, we investigated the risk factors (biosecurity level, animals, exposure from PRRSV-US-infected neighbour herds, semen, herd size, pig density and herd density) for infection with PRRSV-US in a cohort of 1071 sow herds; we used a nested case-control study. The retrospective observation period lasted from June 1996 (when they all were non-infected) to October 1997. Seventy-three non-vaccinated, closed sow herds became infected with the vaccine strain during this period. Each case herd was matched with two control herds from the cohort (controls had not been infected at the time of infection in the case herds). The data were analysed using a Cox-regression model. The hazard of infection increased significantly with exposure from PRRSV-US-infected neighbouring herds, purchase of animals from herds incubating PRRSV-US infection, increasing herd size and purchase of semen from boars at PRRSV-US-infected AI centres. The results are consistent with the modified-live vaccine strain spread to other herds by trade with animals and semen and by neighbour (area) transmission. We suggest that virus spread by aerosols was a frequent mode of transmission.     

4种猪生殖和呼吸综合征灭活疫苗免疫效果比较

猪生殖和呼吸障碍综合征 ( PRRS)是由猪PRRS病毒引起的猪的一种急性高度接触性传染病 ,我国最初于 1 995年报道 ,到目前为止 ,很多地方有此病报道 ,PRRS一旦感染 ,即会在猪场内循环往复、无休止的传播。给养猪生产造成严重的经济损失。目前 ,对该病尚无有效的治疗方法 ,疫苗免疫虽然能在一定程度上减轻疫情的严重情况 ,仍在疫苗的选用上存在不少问题。对于 PRRS弱毒苗疫苗 ,由于其疫苗毒能持续存在数周乃至数月 ,可引起免疫猪长期排毒、散毒 ,或通过胎盘引起先天感染 ;同时 ,疫苗毒株也可出现毒力返强、毒株变异及不同疫苗毒株、疫苗…     

Sow performance in an endemically porcine reproductive and respiratory syndrome (PRRS)-infected farm after sow vaccination with an attenuated PRRS vaccine

The objective of this field study was to evaluate in an endemically porcine reproductive and respiratory syndrome (PRRS) virus-infected farm the reproductive performance of sows after their vaccination with a PRRS attenuated vaccine. In a farrow-to-finish pig farm with history of endemic PRRS virus infection, a total of 200 gilts and sows were used. They were divided in 2 groups of 100 animals. The first group was used as untreated controls, while the animals of the second group were vaccinated against PRRS virus using the attenuated Porcilis PRRS vaccine (Intervet International, The Netherlands) based on European strain. All health and reproductive parameters were recorded from the time of vaccination up to next weaning. No adverse systemic or local reactions or side effects relative to vaccination were noted. Compared to controls, vaccinated sows showed significantly improved farrowing rate (89% versus 78%) and a tendency for fewer returns to oestrus, particularly those at irregular intervals. Fewer sows farrowed prematurely and showed post-partum dysgalactia syndrome, but more live pigs were born and weaned in each litter after vaccination. It was concluded that vaccination of sows with Porcilis PRRS attenuated vaccine in farms with endemic PRRSV infection has beneficial effects on their health and fertility.     

Efficacy of spray-drying to reduce infectivity of pseudorabies and porcine reproductive and respiratory syndrome (PRRS) viruses and seroconversion in pigs fed diets containing spray-dried animal plasma

Three experiments were conducted to evaluate viral inactivation by the spray-drying process used in the production of spray-dried animal plasma (SDAP). In Exp. 1, bovine plasma was inoculated with pseudorabies virus (PRV) grown in PK 15 cells. Three 4-L batches were spray-dried in the same manner and conditions of industrial SDAP production but with laboratory spray-drying equipment. Presence of infectivity was determined before and after spray-drying by microtiter assay in PK 15 cell cultures. Before spray-drying, all three samples contained 10(5.3) tissue culture infectious dose50 (TCID50)/mL of PRV. After four consecutive passages, no viable virus was detected in samples of spray-dried bovine plasma. In Exp. 2, bovine plasma was inoculated with porcine respiratory and reproductive syndrome (PRRS) virus propagated previously in MARC cell culture to provide approximately 10(6.3) TCID50/mL. Three 4-L batches were spray-dried in the same manner as Exp. 1. Before spray-drying, samples contained TCID50 of 10(4.0), 10(3.5), and 10(3.5)/mL, respectively. After four consecutive passages in MARC cell cultures, no viable virus was detected in spray-dried bovine plasma. In Exp. 3, 36 weaned piglets (28 d of age) were fed a common diet for 14 d and were determined to be negative for PRV, PRRS, and porcine parvovirus titer. Afterwards, pigs were allotted to six pens with six pigs per pen and fed diets containing either 0 or 8% SDAP (as-fed basis) for 63 d. The SDAP used in the feed contained antibody (titer 1:400) against porcine parvovirus. Blood samples were collected from pigs on d 0 and 63 to determine whether feeding SDAP caused seroconversion and development of antibodies against parvovirus, PRRS, or PRV. Inclusion of SDAP in the diet improved growth of pigs without seroconversion. Spray-drying conditions used in this study were effective in eliminating viable pseudorabies and PRRS viruses from bovine plasma. In this study, feeding SDAP that contained functional antibodies did not promote seroconversion in na?ve animals.     

Effect of orally administered Lactobacillus casei on porcine reproductive and respiratory syndrome (PRRS) virus vaccination in pigs

The purpose of this study was to determine whether intranasal/oral administration of probiotics can assist vaccination efficacy against an important swine pathogen, porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV). A controlled challenge trial was performed employing: (a) pigs vaccinated against PRRS and treated with a Lactobacillus casei, (b) pigs vaccinated against PRRS only, (c) pigs treated with L. casei only, and (d) pigs neither vaccinated against PRRS nor treated with L. casei. All pigs were challenged intranasally with a wild PRRSV strain. There was no difference in clinical signs or rectal temperature among the four groups. However, pigs that received L. casei gained significantly more weight than pigs that did not. Vaccinated pigs did not gain more weight than nonvaccinated pigs. Vaccinated groups had significantly fewer viraemic pigs on days post-challenge 4, 11 and 17 than nonvaccinated groups of pigs. There was no effect of probiotic on prevalence or duration of viraemia. Among viraemic pigs, there was no significant difference in mean log base(10) titer of PRRS virus among groups. These results suggest that orally administered L. casei does not affect immune response in such a way as to affect PRRS viraemia or nasal shedding. However, it still appears to provide significant benefit when administered during vaccination as indicated by the higher bodyweight gain following PRRS virus infection.     

猪繁殖与呼吸综合征病毒分子生物学研究进展

猪繁殖与呼吸综合征病毒(PRRSV)是引起猪繁殖与呼吸综合征的病原体,本文对PRRSV的分子生物学研究进展进行了综述,主要包括PRRSV的基因组结构、病毒蛋白及其功能、抗原变异等,旨在为诊断技术、免疫机理研究、疫苗设计与疫病防制提供借鉴.     

Heterologous challenge with porcine reproductive and respiratory syndrome (PRRS) vaccine virus: no evidence of reactivation of previous European-type PRRS virus infection.

In Denmark, a porcine reproductive and respiratory syndrome virus (PRRSV) control programme, comprising vaccination of seropositive herds with a live American type PRRSV vaccine, was started in 1996. In several of these herds, spread of vaccine virus from vaccinated 3-18 week old pigs to non-vaccinated sows was demonstrated by the isolation of vaccine virus from fetuses and stillborn piglets. Surprisingly, sows infected with the American type vaccine strain consistently exhibited significantly stronger serological responses towards European type PRRSV than American type PRRSV. In order to elucidate whether the unexpectedly strong serological reaction towards European-type PRRSV in American type PRRSV infected sows was due to a booster reaction, or reactivation of an unrecognized, latent infection in the sows with European type PRRSV, a challenge study with the vaccine was carried out. In this study, the stronger serological response towards European type PRRSV than towards American type PRRSV was reproduced, and reactivation of the previous natural infection with European PRRSV could neither be demonstrated by virus isolation nor by RT-PCR. So, the increase in antibody titers towards European PRRSV in previously European PRRSV infected pigs after challenge with the vaccine strain seems to be the result of a boosting effect on the immune system, induced by the heterologous vaccine PRRSV strain.     

A modified immunoperoxidase assay for detection of antibody porcine reproductive and respiratory syndrome (PRRS) virus in swine sera

MARC-145 cell monolayers infected with PRRS virus were fixed in 3% neutral buffered formalin and embedded in paraffin. The sections were stained by avidin-biotin complex immunoperoxidase (ABC) method. Test sera were applied to sections as primary antibodies. The positive reactions were detected by ABC method and indirect immunofluorescent assay (IFA). There was good correlation between ABC and IFA, and the titers in ABC were higher than those in IFA. The present results indicate that the immunohistochemical staining is a useful test for the detection and quantitation of PRRS virus antibody in swine sera as well as IFA.     

Clinical signs and their association with herd demographics and porcine reproductive and respiratory syndrome (PRRS) control strategies in PRRS PCR-positive swine herds in Ontario

The purposes of this study were to describe the clinical signs observed in PRRS positive herds during a porcine reproductive and respiratory syndrome (PRRS) outbreak in Ontario and to determine associations between these clinical signs and herd demographics and PRRS control strategies. All PRRS polymerase chain reaction-(PCR)-positive submissions to a diagnostic laboratory between September 1, 2004 and August 31, 2007 were identified (n = 1864). After meeting eligibility requirements and agreeing to voluntary study participation, producers from 455 of these submissions were surveyed for information on clinical signs observed in their herds, herd demographics, and PRRS control strategies used in their herds at the time that the PCR-positive samples were taken. Larger herd size was associated with an increased risk of reporting abortion, weakborn piglets, off-feed sows, and sow mortality in sow herds, and with an increased risk of reporting mortality in finishing herds. When disease control strategies were examined, use of a commercial PRRS vaccine in sows and gilts was associated with a decreased risk of reporting weakborn pigs and high pre-weaning mortality, while the use of serum inoculation in breeding animals was associated with an increased risk of reporting off-feed sows and sow mortality. Providing biofeedback of stillborn/mummified piglets, placenta or feces to gilts was associated with an increased risk of reporting respiratory disease and mortality in finishing pigs while all-in/all-out flow in farrowing rooms was associated with an increased risk of reporting sow mortality and weakborn piglets.     

南方三省猪繁殖与呼吸综合征病毒分子流行病学调查研究

根据VR2332和CH-1aE基因序列设计一对特异性引物，对广西、广东、海南三省15个猪繁殖与呼吸综合征病毒毒株E基因进行RT-PCR扩增，将扩增出的668bp片段插入pMD18-T载体中，进行序列测定。结果显示，15个毒株的E基因核苷酸序列之间的相似性为84．1％～100％，推导编码的氨基酸序列之间的相似性为81．1％～100％；与VR2332、CH-1a、LV株核苷酸之间的相似性分别为85．4％～98．5％、87．1％～96．2％、62．5％～63．8％，与VR2332、CH-1a、LV株氨基酸之间的相似性分别为83．1％～95．5％、86．1％～95．0％、51．7％～57．2％，表明15个毒株的E基因区域变异较大，均属美洲型。将15个流行毒株与国内外已发表的37株猪繁殖与呼吸综合征病毒相应序列进行比较，建立的遗传进化树表明这15个毒株分别属于3个亚群。推导编码氨基酸的比较结果表明，分别属于不同亚群的不同地区流行的猪繁殖与呼吸综合征病毒毒株在E基因编码蛋白的潜在糖基化位点数目、抗原表位区域和与毒力相关的氨基酸等均存在变异。