Considerations for design and implementation of vaccine field trials for novel foot-and-mouth disease vaccines

Vaccines are commonly used to control Foot-and-Mouth Disease (FMD) in endemic regions and form an important part of contingency plans for FMD-free countries. Conventional FMD vaccines have numerous limitations, and the U.S. government supports the development of next-generation vaccines. In the U.S., vaccine efficacy is typically demonstrated through experimental vaccination and challenge of animals using the World Organization for Animal Health (OIE) standards. Although conventional challenge and immunogenicity studies provide useful information, they have limitations and results do not always accurately predict field performance. Consequently, there is a need to test next-generation vaccines under field conditions to gain a better understanding of field performance to inform policy decisions and support their viability as a commercial product.In June 2017, an expert consultation was organised to discuss and define an optimal field study design for novel FMD vaccines. Cattle were the primary species considered, although parallel strategies for swine and small ruminants were also discussed. Many methodological and logistical considerations in the study design were identified, including: (1) study site selection and the importance of baseline studies to understand exposure risk, (2) ethics of using a placebo and assessing equivalence with conventional vaccines, (3) merits of using individual randomised versus cluster randomised trials, (4) preventive versus reactive vaccination, and (5) methods of randomisation and blinding.The proposed optimal study design was a multicentre (i.e. farm), three-arm, double-blind randomised controlled trial comparing groups receiving the novel vaccine to a conventional vaccine group and a placebo group. Large farms in areas of high exposure risk were identified as ideal study sites, and the primary study outcome was susceptibility to disease or infection, during a six-month observation period, following a single dose of vaccine. This report provides a summary of the important issues to consider when designing a field efficacy study in livestock and proposes a study design that could be utilised for novel FMD vaccines.     

某市市售畜肉类食品中多氯联苯污染水平研究

目的 了解某市市售畜肉类食品中多氯联苯(PCBs)的污染水平.方法 于2008年8-12月采集某市28件猪、牛、羊样品,参照美国国家环保局EPA1668A方法,利用索式抽提装置和FMS自动纯化系统分别对样品进行提取和净化,通过高分辨气相色谱-高分辨双聚焦磁式质谱仪(HRGC-HRMS)对样品中的多氯联苯进行检测分析,采用同位素稀释的定量内标法对样品中的12个二(噁)英类多氯联苯(dioxin-like PCBs)和6个指示性多氯联苯进行定性和定量分析.结果 牛肉、猪肉、羊肉中的18个多氯联苯化合物总含量分别为1 607.60、435.82、505.17 pg/g脂肪.其中,二(噁)英类PCBs含量分别为456.19、46.37、77.50 pg/g脂肪.指示性PCBs化合物含量分别为1 151.41、389.45、427.67pg/g脂肪.牛肉、猪肉、羊肉样品多氯联苯毒性当量(TEQ)中位数值分别为0.84、0.15、0.28 Pg/g脂肪.三类样品多氯联苯的TEQ(中位数值)均低于欧盟的行动标准限量值.在所有样品中PCB118均是对总PCBs含量贡献最大的化合物单体,而PCB126则是对毒性当量贡献最大的化合物单体.结论 在采集的28个样品中有6个样品超过了欧盟行动标准的限量值,说明该市市售畜肉类食品存在一定程度的污染,应该进行溯源研究和污染原因的排查,以保障食品安全.

Abstract：

Objective To investitgate the level of polychlorinated biphenyls in retail livestock meat.Methods Totally 28samples of three kinds of meat including of beef,pork and mutton were collected during Aug-Dec.,2008.Twelve dioxin-like polychlorinated biphenyls(DL-PCBs)and six marker PCBs were extracted by Soxhlet extractor,cleaned up by FMS and qualitative and quantitative analyzedsis by isotope dilution high-resolution gas chromatography/high resolution mass spectrometry(HRGC/HRMS).Results Levels of total 18 compounds including of 12 DL-PCBs and indicator PCBs in beef,pork and mutton were1 607.60 Pg/g fat,435.82 pg/g fat,and 505.17 pg/g fat respectively,DL-PCBs concentration were 456.19 Pg/g fat,46.37 Pg/g fat and 77.50 pg/g fat respectively.Maker-PCBs concentration were 1 151.41 pg/g fat,389.45pg/g fat and 427.67 pg/g fat respectively.The levels of PCB toxicity equivalent(TEQ)(the median value)were:0.84 pg/g fat in beef,0.15 pg/g fat in pork,0.28 pg/g fat in mutton respectively.The TEQ concentration of PCB(median value)was lower than the EU action level limit value.In all samples,PCB118 was the greatest contributor to the total contaminated concentration,and PCB126 was the dominant contributor to toxicity equivalent(TEQ).Six of 28 samples exceeded the limit value of the EU action level.Conclusion The results show that PCBs contamination exists in a city from the six samples exceeding the EU standard limit.It should take measures to explore the cause of contamination of PCBs compounds and control the pollution in order to guarantee food safety effectively.     

固相萃取高效液相色谱法同时测定禽畜组织中雌雄性激素残留的研究

目的:固相萃取高效液相色谱法同时测定禽畜组织中已烯雌酚(DES)、丙酸睾酮(TES)的残留量。方法:固相萃取小柱为AlltechExtract-cleancolumnsC18, 200mg/4 .0ml,洗脱液为甲醇;色谱柱为SUPELCODiscoveryC18 5μm250×4 .6mm,流动相为:甲醇∶水=85∶15(v/v),流速为1 0ml/min,二极管阵列检测器,检测波长为245nm。结果:该方法的线性范围为: 0 5 ~10 0μg/ml;标准曲线线性良好,其回归方程及相关系数r分别为已烯雌酚:Y=61 .31042X+2. 38615,r=0 99999;丙酸睾酮:Y=60. 42778X-0 20465,r=0 .99994。最低检出限分别为:已烯雌酚9. 5μg/kg;丙酸睾酮8 .4μg/kg;回收率在92% ~103% 之间,相对标准偏差小于1 .3%。结论:该方法操作简便、快捷,是禽畜类食品激素残留的快速而准确的检测方法。     

新疆阜康县草畜平衡动态监测与调控研究

本研究利用1991—1993年在新疆阜康县不同草地类型上观测到的牧草产量、环境资料与地面光谱、气象卫星资料等,进行了多重相关分析.结果表明,不同类型的草地产量与环境因子和各种绿度值间存在着显著相关性(ρ<0.05),相关系数(r)均达到0.84以上,并通过F检验.又利用作者研制开发的遥感环境综合技术系统(RSECTS)进行了草地资源的系列动态监测与分析,建立了综合估产模型及相应的可利用牧草估产模型等;—同时,进一步运用RSECTS建立了草地利用和草畜平衡监测模式及进行了草畜平衡与管理诸方面分析和论证,基本实现了从初级生产到次级生产对草地资源的遥感动态监测,解决了许多有关技术性难题,找出草畜系统管理中存在的主要问题,制定了调控措施,为草地资源的科学管理与合理利用,提供了坚实依据和可靠方法.     

畜、禽组织中己烯雌酚残留量RP-HPLC测定条件研究

目的高效液相色谱测定畜禽组织中己烯雌酚残留量.方法样品经甲醇提取过滤,经中性氧化铝层析柱除杂,浓缩后再溶解,高效液相色谱二极管阵列检测,于238 nm测定其吸光度.结果在优化的实验条件下,己烯雌酚的最低检出浓度(S/N=3)6.18×10-2 μg/ml;线性相关系数(r)0.9997;变异系数＜5%(n=9);标准回收率为85%,94.63%;RSD为0.70%,2.99%.结论经实验证明,研究条件拟定的实验方案可以快速、灵敏、稳定、定量的检测畜、禽组织中己烯雌酚残留量.     

动物及健康人肠道共生的大肠埃希菌耐药性及产生原因分析

目的了解目前动物和人肠道共生的大肠埃希菌耐药性,分析其产生的原因。方法从甘肃、湖北、北京、山东、四川等地相对封闭的养殖场及养殖场附近的健康人群采集鸡、猪、鱼、人粪便样本,分离大肠埃希菌。用AP I20E鉴定条鉴定怀疑为大肠埃希菌的菌种,采用KB纸片法检测生化鉴定为大肠埃希菌的菌株的耐药性,利用WHONET 5.3软件进行药敏试验数据分析。用脉冲场凝胶电泳技术检测具有相似耐药谱型的大肠埃希菌菌株间的同源性。结果①共收集571株大肠埃希菌,其中从海水养殖鱼类和淡水养殖鱼类分离31株,另从海水养殖鱼类和淡水养殖鱼类分离嗜水气单胞菌株57株;②来源鸡的大肠埃希菌对所有检测的抗菌药物的耐药率最高;③除β-内酰胺类抗生素和阿米卡星外,鸡、猪和人来源菌株的耐药率表现为高、中、低现象,对老的一些抗菌药物和喹诺酮类抗菌药物尤其明显;不同地区分离株的耐药性也有较大的差异;④本次调查首次在国内养鸡场发现产ESBL大肠埃希菌,并且非常多见;⑤嗜水气单胞菌和大肠埃希菌的耐药性有较大的差异,47株耐药谱型相近的菌株中发现了三组基因水平同源性菌株(相似度大于95%)。结论①从不同地区、不同种类动物分离菌株的耐药性不同,与抗生素的使用情况相关。目前我国家禽养殖业滥用喹诺酮类和β-内酰胺类尤其是三代头孢菌素类抗生素的现象较为普遍,应该加以严格控制;②不同菌种的生物学特性不同,导致耐药性不同;③同源性分析发现耐药菌株可在同一种类动物间传播,不同类动物的大肠埃希菌之间可能存在耐药基因的水平传播;④应当加强养殖动物分离的大肠埃希菌耐药性监测。     

Heat stress on reproductive function and fertility in mammals

In most mammalian species including cattle, heat stress has deleterious effects on nutritional, physiological and reproductive functions. Exposure of animals to a hot environment causes an increase in body temperature in mammals, including domestic animals. High ambient temperature also causes a decrease in the length and intensity of estrus by disturbing ovarian function as well as decreasing pregnancy rate after artificial insemination. Therefore, it is important to understand the effects of heat stress on reproductive function in order to improve the production of domestic animals. Heat stress decreases appetite, weight gain, and milk yield in dairy cattle. It also adversely affects the reproductive performance of both sexes. In males, it reduces spermatogenic activity, while in females it adversely impacts oogenesis, oocyte maturation, fertilization development and implantation rate. Detection and evaluation of the deteriorating effects of heat stress on reproductive organs and cells can help to design measures to prevent them and improve reproductive functions. In this review, we discuss the impacts of heat stress on reproductive functions.     

Characterization of tetracycline and methicillin resistant Staphylococcus aureus strains in a Spanish hospital: Is livestock-contact a risk factor in infections caused by MRSA CC398?

Tetracycline-resistance (Tet^R) has been postulated as a marker of the livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) lineage CC398. Objectives of the study: to determine the spa-types and assigned MLST clonal complexes (CCs) among all 98 MRSA-Tet^R strains recovered during 2011–2012 (from different patients) in a Spanish Hospital, analyzing the possible correlation with livestock-contact of the patients. All 98 strains were assigned to 9 CCs: CC398 (60.2%), CC1 (19.4%), CC5 (12.2%), and other CCs (8.2%). The 98 patients were classified into three groups: (A) contact with livestock-animals (n = 25); (B) no-contact with livestock-animals (n = 42); (C) no information about animal contact (n = 31). A significant higher percentage of CC398 strains was obtained in group A (76%) than in group B (50%) (p < 0.05), being the percentage in group C of 61.3%. Most of MRSA-Tet^R-CC398 strains presented a multi-resistance phenotype, including erythromycin, clindamycin, and ciprofloxacin, and the most prevalent detected genes were tet(M) and erm(C). Three strains presented the phenotype macrolide-susceptibility/lincosamide-resistance and contained the vga(A) gene. MRSA-CC1 strains showed higher percentages of erythromycin/clindamycin resistance (95%/89%) than MRSA-CC398 strains (58%/63%), and this resistance was usually mediated by erm(C) gene. Most of MRSA-CC5 strains showed resistance to ciprofloxacin, tobramycin/kanamycin and erythromycin. None of the strains presented the genes lukF/lukS-PV, tsst-1, eta, etb or etd. All MRSA-CC398 strains lacked the genes of the immune-evasion-cluster, but MRSA-CC1 strains carried these genes (type E). In conclusion, although MRSA CC398 is detected in a significant higher proportion in patients with livestock-contact; its detection in people without this type of contact also indicates its capacity for human-to-human transmission.     

家畜传染源控制为主的血吸虫病防治策略实施效果

目的探索湖沼型地区血吸虫病防治策略及有效干预措施,评估家畜传染源控制为主的综合防治措施效果。方法在3个典型的湖沼型地区选取22个乡镇128个血吸虫病流行村,以洲滩和村垸为建设单元,实施易感地带封洲禁牧、建立定点牧场、开展舍饲圈养等以家畜传染源控制为主的综合防治措施,观察干预措施前后人畜病情与螺情变化,评估干预措施对血吸虫病的控制效果。结果实施家畜传染源控制为主的综合防治措施2~3年后,主要传染源(牛)饲养户数和数量分别减少了42.86%和50.30%,钉螺孳生环境的野粪密度和阳性率分别减少了89.72%和84.51%,人、畜(牛)、钉螺感染率分别下降了51.93%、74.90%和92.42%,环境安全性提高了97.93%。干预措施前后效果有显著性差异(P0.05)。结论结合当地经济开发,因地制宜地采取以家畜传染源控制为主的综合防治措施,对湖沼型地区的血吸虫病传播控制具有重要作用。     

Sequence Analysis of the Second Internal Transcribed Spacer (ITS2) Region of rDNA for Species Identification of Trichostrongylus Nematodes Isolated From Domestic Livestock in Iran

Background

Infectivity of herbivores with Trichostrongylus nematodes is widespread in many countries, having a major economic impact on breeding, survivability, and productivity of domestic livestock. This study was carried out on Trichostrongylus species isolated from domestic livestock in order to develop an easy-to-perform method for species identification.

Methods

Trichostrongylus isolates were collected from sheep, goat, cattle, and buffaloes in Khuzestan Province, southwest Iran. Primary species identification was carried out based on morphological characterization of male worms. PCR amplification of ITS2-rDNA region was performed on genomic DNA and the products were sequenced. Phylogenetic analysis of the nucleotide sequence data was conducted employing Bayesian Inference approach. Consequently, a restriction fragment length polymorphism (RFLP) profile was designed to differentiate Trichostrongylus species.

Results

A consensus sequence of 238 nucleotides was deposited in the GenBank for Iranian isolates of Trichostrongylus species including T. colubriformis, T. capricola, T. probolurus and T. vitrinus. The designated RFLP using restriction enzyme TasI could readily differentiate among species having different ITS2 sequence. The molecular analysis was in concordance with morphological findings.

Conclusion

Phylogenetic analysis indicated a close relationship among the sequences obtained in this study and reference sequence of relevant species. ITS2-RFLP with TasI is recommended for molecular differentiation of common Trichostrongylus species.