诱蛋白基因敲除对雄性小鼠细胞因子水平的影响

细胞因子是一系列参与造血、免疫细胞发育、炎症反应和免疫应答等的调节蛋白.有的细胞因子可直接影响睾丸细胞的功能.有研究显示,细胞因子在睾丸的发育和发挥正常功能方面有着重要的作用[1].致炎细胞因子包括白细胞介素(IL)-1和IL-6对于生精细胞的分化和睾丸甾体激素的合成有着直接的作用.干细胞因子、白血病抑制因子和参与造血作用的细胞因子对于精子发生也有一定的作用.本课题组研究发现,attractin(Atrn)基因敲除后小鼠的生育能力有不同程度的下降.本实验旨在了解Atrn基因敲除后小鼠的细胞因子水平变化,为进一步研究Atrn基因对雄性生殖的影响机制提供依据.     

睾丸特异性基因BAFL在人和小鼠中的表达及其生物信息学分析

目的 筛选与精子发生相关的基因.方法 将4d、9d、18d、35d、54d和6月龄小鼠睾丸组织cDNA探针与Affymetrix全基因组芯片进行杂交,筛选出差异表达的基因.利用网络信息资源对该基因进行生物学信息分析.RT-PCR分析该基因在小鼠睾丸不同发育阶段4d、9d、11d、14d、18d、21d、38d、6月龄及人和小鼠不同组织心、肝、脾、肺、肾、脑、附睾和睾丸中的表达.结果 芯片结果分析筛选出1个差异表达杂交点,生物信息学分析发现该差异点是BAFL基因,该基因全长527bp,含有273bp的完整ORF,编码90个氨基酸、相对分子量(Mr)为10.266kDa的蛋白质.RT-PCR分析表明小鼠mBAFL基因在小鼠21d龄睾丸及之前没有表达,在35d龄睾丸后开始高表达并特异性地表达于睾丸组织.人hBAFL基因在所检测的8种组织中,也只在睾丸组织中表达.结论 BAFL基因为睾丸特异性基因,小鼠mBAFL的表达与小鼠精子发生的过程一致,可能在精子发生中起重要作用.     

乳腺癌中黏着斑激酶、抑癌基因PTEN编码蛋白的表达与生物学行为相关性分析

目的 研究乳腺癌组织中黏着斑激酶（FAK）和PTEN蛋白的表达与肿瘤分化、浸润转移的关系，揭示细胞信号转导系统与乳腺癌发生发展的关系，同时为乳腺癌的基因治疗提供依据。方法 应用免疫组织化学SP法检测92例乳腺癌组织和30例乳腺良性病变组织中FAK、PTEN的表达情况及其与临床病理参数的关系。结果 （1）在92例乳腺癌中FAK和PTEN的阳性表达率分别为69．6％和51．1％，与对照组比较，差异有统计学意义（P〈0．01）；（2）FAK表达与乳腺癌肿瘤大小、腋窝淋巴结转移、临床分期呈正相关（P〈0．01），PTEN表达与乳腺癌组织学分级、腋窝淋巴结转移、临床分期呈负相关（P〈0．05）；（3）乳腺癌组织FAK表达与PTEN表达呈负相关（P〈0．01）。结论 乳腺癌FAK的高表达和PTEN的缺失表达与肿瘤发生发展、浸润转移密切相关；检测这些指标，有助于判断乳腺癌的恶性程度及生物学行为。     

泛耐药鲍曼不动杆菌PBP1A、CarO及β-内酰胺酶的编码基因分析

目的了解一株泛耐药鲍曼不动杆菌（js01株）可能存在的β-内酰胺类药物耐药机制。方法对自2011年12月宁波市第一医院住院患者的痰样本js01株分离,用gyrA和parC基因PCR扩增、测序和BLASTn比对确认菌种。用PCR法分析33种β-内酰胺酶基因（13种A类酶基因、10种B类酶基因、2种C类酶基因、8种D类酶基因）和插入序列与β-内酰胺酶编码基因连锁检测以及CarO膜孔蛋白编码基因。再用分段PCR法扩增PBP1A编码基因,双向测序后拼接成全长序列。结果js01株检出β-内酰胺酶TEM-1、ADC-30、OXA-23和OXA-66编码基因。插入序列与β-内酰胺酶编码基因连锁检测显示ISabal-ADC-30和ISabal—OXA-23为阳性。js01株carO基因序列与鲍曼不动杆菌敏感株（SDF）相比存在有义突变,氨基酸序列一致率为76．0％（189／249）,存在3个氨基酸缺失。is01株PBP1A编码基因序列与SDF株相比存在有义突变,氨基酸序列的一致率为99．6％（848／851）,存在3个氨基酸变异,但js01株PBP1A蛋白分子立体结构比SDF株丢失2个螺旋结构。结论本株鲍曼不动杆菌对β-内酰胺类药物耐药主要与该菌株管家基因（PBP1A、CarO编码基因）突变与可移动遗传元件介异的β-内酰胺酶编码基因有关。     

阴沟肠杆菌外膜孔蛋白基因缺失合并β-内酰胺酶和Ⅰ类整合子所致多重耐药性分析

目的 了解临床分离阴沟肠杆菌膜孔蛋白基因缺失合并β-内酰胺酶和Ⅰ类整合子所致耐药的特点及其分布.方法 收集2008年1月至2011年5月自临床感染患者分离的112株阴沟肠杆菌.应用vitek-2 compact鉴定细菌,k-b法进行药敏试验,改良hodge试验、美罗培南改良三维实验和edta-美罗培南纸片协同试验筛选产碳青霉烯酶菌株.多重pcr分别检测4种esbls基因、6种ampc酶基因、4种碳青霉烯酶基因及4组oxa-like基因,单一pcr检测isecpl、ompk35/36、ndm-1、oxa-48,并对Ⅰ类整合子可变区进行pcr扩增及序列分析.结果 6株(5.4％)改良hodge试验阳性,14株(12.5％)美罗培南改良三维试验阳性,未检出碳青霉烯酶基因.29株(25.9％)esbls基因阳性,其中,ctx-m基因上游均检测到isecpl,并检测到2株产oxa-1型esbls阴沟肠杆菌.ampc酶基因阳性45株(40.2％),以mir-3型为主(37/45,82.2％).共检出22株Ⅰ类整合子基因阳性菌株,其中16株可变区扩增阳性.扩增出4种耐药基因盒,aadb-aada2(1 000 bp)9株,dfra 15 (700 bp)5株,aadal(1 000 bp)2株,有l株菌同时携带4种耐药基因盒.所有菌株均合并有膜孔蛋白ompk35和/或ompk36基因缺失,并呈现多重耐药.结论 阴沟肠杆菌对碳青霉烯类抗生素的敏感性降低主要与其高产ampc酶、esbls并存在膜孔蛋白ompk35和/或ompk36基因缺失有关,且Ⅰ类整合子参与阴沟肠杆菌的多重耐药. abstract： objective to investigate the drug resistance and its distribution induced by β-lactamases and class Ⅰ integrons with the deficiency of omp genes in enterobacter cloacaes.methods totally 112 strains of enterobacter cloacaes were isolated during january 2008 and may 2011.the identification of strains was performed by using vitek-2 compact automatic system; and antibiotic susceptibility was determined by k-b method.isolates of e.cloacae were screened for carbapenemases by modified hodge test,improved three dimensional test and edta-meropenem synergy test.genes encoding ampc β-lactamase,metallo-β-1actamases (mbls) and oxa-like β-1actamases were screened by multiple pcr.single pcr was used to detect isecpl,ompk35/36,ndm-1 and oxa-48.the variable regions of class Ⅰ integrons were amplified and sequenced.results among 112 isolates,6 (5.4％) demonstrated positive in the modified hodge test and 14 ( 12.5％ ) were positive in the improved three-dimensional test.no carbapenemases gene was found.there were 29(25.9％ ) strains positive for esbls genes,isecpl was found in the upstream of all the ctx-m-type esbls; oxa-1 esbls were detected in 2 isolates.ampc β-lactamase genes were positive in 45 (40.2％) strains,and 82.2％ (37/45) were mir-3 type.twenty two isolates carried class Ⅰ integrons,and four different cassettes arrangements were identified within 16 strains:9 isolates harbored aadb-aada2 ( 1 000 bp),5 isolates with dfral5 (700 bp),2 isolates with aadal ( 1 000 bp).one isolate harbored all the above gene cassettes.the deficiency of ompk35/36 was found in all strains.conclusion esbl,ampc β-lactamase and the deficiency of ompk35/36 are correlated with the resistance to carbapenems in enteobacter clocace,and class Ⅰ integrons may also partly account for the multidrug-resistance.     

肝癌代谢重编程相关基因富集分析及ATP柠檬酸裂解酶表达的临床意义

目的 筛选参与肝细胞癌(HCC,简称肝癌)肿瘤进展的代谢重编程相关基因,明确HCC组织标本中ATP柠檬酸裂解酶(ACLY)表达情况,并纳入GEO数据,分析其与HCC临床病理指标的相关性及其在HCC生存预后中的作用.方法 下载TCGA数据库中的HCC表达数据,将50对癌组织与癌旁配对组织样本纳入差异表达基因分析,获得全基...     

CYP3A4*1G基因多态性对患者术后舒芬太尼用量和镇痛效果影响的Meta分析

目的 评价细胞色素P450酶3A4*1G（CYP3A4*1G）的基因多态性对患者术后舒芬太尼用量及镇痛效果的影响。
方法 检索PubMed、Embase、Wiley Online Library、Cochrane Library、中国知网、维普、万方、中国生物医学文献数据库等数据库,收集由建库至2021年8月发表的关于CYP3A4*1G基因多态性对术后采用舒芬太尼镇痛影响的研究,按照Cochrane指导手册的方法选择文献、提取资料及评价研究质量,采用RevMan 5.4软件进行Meta分析。
结果 共纳入9篇文献,共计867例患者,其中CYP3A4*1G突变组351例,未突变组516例。Meta分析结果显示,与CYP3A4*1G突变组比较,未突变组术后24、48 h的舒芬太尼用量均明显增加（SMD=0.32,95%CI 0.19～0.46,P<0.001）,术后24 h VAS疼痛评分明显升高（SMD=0.30,95%CI 0.13～0.47,P<0.001）。两组不良反应发生率差异无统计学意义。
结论 CYP3A4*1G基因多态性可明显减少患者术后舒芬太尼用量,降低术后24 h VAS疼痛评分,对术后不良反应无明显影响。     

产甘油假丝酵母烯醇化酶基因的克隆及序列分析

从产甘油假丝酵母(Candida glycerinogenes)基因文库中分离了一个含烯醇化酶基因(CgENO1)的克隆子.插入片段全长2 456 bp,包含一段1 314 bp的没有内含子的蛋白质编码区,编码一个含438个氨基酸残基的多肽链,其氨基酸序列与来源于酿酒酵母的烯醇化酶相似性为74.3%.多重序列比对显示,产甘油假丝酵母烯醇化酶(CgENO1)含有酵母烯醇化酶全部保守区.对编码区上下游序列分析显示,克隆片段含有典型的酵母基因上下游调控区,是一个完整的酵母新基因.     

人退变腰椎间盘中细胞凋亡与Bax及半胱胺酸蛋白酶蛋白3基因的表达

目的 检测人腰椎间盘组织中的细胞密度、细胞凋亡率以及Bax和半胱氨酸蛋白酶蛋白3(Caspase-3)的表达,为深入了解人腰椎间盘退变的机制提供实验依据,并为将来通过生物学方法 延缓腰椎间盘退变提供新的思路.方法 实验组30个椎间盘标本(L2～S1)来自27例行后路腰椎间盘切除椎间融合手术自愿捐赠的患者,男18例,女9例;年龄30～72岁,平均51.09岁.所有病变节段均经MRI证实,患者术前均未接受椎间盘造影、胶原酶髓核溶解或椎间盘激光汽化术.对照组20个标本(L2～S1)来自5例青年男性意外死亡者新鲜尸检腰椎间盘;年龄24～37岁,平均30.83岁.采用HE染色观察凋亡软骨细胞、凋亡小体和细胞密度,TUNEL染色法检测人腰椎间盘中的凋亡细胞率,用SP免疫组织化学法检测Bax及Caspase-3表达,图像分析Bax及Caspase-3的平均灰度值.结果 HE染色示对照组、实验组软骨终板和髓核内的平均细胞密度分别为(17.16±1.22)、(12.41±0.95)个/HP,二者差异有统计学意义(P＜0.01).TUNEL染色观察示对照组的软骨终板与髓核内的平均凋亡细胞率为6.97%±0.92%,低于实验组的12.59±0.95%(P＜0.01).SP免疫组织化学染色示对照组髓核内Bax、Caspase-3染色阳性细胞率分别为11.02%4±1.18%和9.01%±1.00%,均低于实验组的19.29%±1.18%和15.07%±0.97%,差异均有统计学意义(P＜0.01).对照组腰椎间盘髓核内Bax、Caspase-3的平均灰度值分别为187.33±7.88和185.68±3.26,实验组分别为124.98±6.69和160.13±4.37,两组间比较差异有统计学意义(P＜0.01).将全部腰椎间盘标本进行Pearson相关分析,对照组和实验组腰椎间盘凋亡细胞率与细胞密度间成负相关,相关系数r分别为-0.88和-0.93(P＜0.01)两组髓核内Bax、Caspase-3阳性细胞率与凋亡细胞率之间成正相关,相关系数r分别为0.83和0.91(P＜0.01).结论 细胞密度下降参与了人腰椎间盘的退变过程,Bax和Caspase-3的表达上调在人腰椎间盘髓核细胞的凋亡过程中有一定作用.     

Seasonal risk of low pathogenic avian influenza virus introductions into free‐range layer farms in the Netherlands

Poultry can become infected with avian influenza viruses (AIV) via (in) direct contact with infected wild birds. Free‐range chicken farms in the Netherlands were shown to have a higher risk for introduction of low pathogenic avian influenza (LPAI) virus than indoor chicken farms. Therefore, during outbreaks of highly pathogenic avian influenza (HPAI), free‐range layers are confined indoors as a risk mitigation measure. In this study, we characterized the seasonal patterns of AIV introductions into free‐range layer farms, to determine the high‐risk period. Data from the LPAI serological surveillance programme for the period 2013–2016 were used to first estimate the time of virus introduction into affected farms and then assess seasonal patterns in the risk of introduction. Time of introduction was estimated by fitting a mathematical model to seroprevalence data collected longitudinally from infected farms. For the period 2015–2016, longitudinal follow‐up included monthly collections of eggs for serological testing from a cohort of 261 farms. Information on the time of introduction was then used to estimate the monthly incidence and seasonality by fitting harmonic and Poisson regression models. A significant yearly seasonal risk of introduction that lasted around 4 months (November to February) was identified with the highest risk observed in January. The risk for introduction of LPAI viruses in this period was on average four times significantly higher than the period of low risk around the summer months. Although the data for HPAI infections were limited in the period 2014–2018, a similar risk period for introduction of HPAI viruses was observed. The results of this study can be used to optimize risk‐based surveillance and inform decisions on timing and duration of indoor confinement when HPAI viruses are known to circulate in the wild bird population.     

Isolation of highly pathogenic H5N6 avian influenza virus in Southern Vietnam with genetic similarity to those infecting humans in China

Since 2013, H5N6 highly pathogenic avian influenza viruses (HPAIVs) have been responsible for outbreaks in poultry and wild birds around Asia. H5N6 HPAIV is also a public concern due to sporadic human infections being reported in China. In the current study, we isolated an H5N6 HPAIV strain (A/Muscovy duck/Long An/AI470/2018; AI470) from an outbreak at a Muscovy duck farm in Long An Province in Southern Vietnam in July 2018 and genetically characterized it. Basic Local Alignment Search Tool (BLAST) analysis revealed that the eight genomic segments of AI470 were most closely related (99.6%–99.9%) to A/common gull/Saratov/1676/2018 (H5N6), which was isolated in October 2018 in Russia. Furthermore, AI470 also shared 99.4%–99.9% homology with A/Guangxi/32797/2018, an H5N6 HPAIV strain that infected humans in China in 2018. Phylogenetic analyses of the entire genome showed that AI470 was directly derived from H5N6 HPAIVs that were in South China from 2015 to 2018 and clustered with four H5N6 HPAIV strains of human origin in South China from 2017 to 2018. This indicated that AI470 was introduced into Vietnam from China. In addition, molecular characteristics related to mammalian adaptation among the recent human H5N6 HPAIV viruses, except PB2 E627K, were shared by AI470. These findings are cause for concern since H5N6 HPAIV strains that possess a risk of human infection have crossed the Chinese border.     

Genetic relationship between poultry and wild bird viruses during the highly pathogenic avian influenza H5N6 epidemic in the Netherlands, 2017–2018

In the Netherlands, three commercial poultry farms and two hobby holdings were infected with highly pathogenic avian influenza (HPAI) H5N6 virus in the winter of 2017–2018. This H5N6 virus is a reassortant of HPAI H5N8 clade 2.3.4.4 group B viruses detected in Eurasia in 2016. H5N6 viruses were also detected in several dead wild birds during the winter. However, wild bird mortality was limited compared to the caused by the H5N8 group B virus in 2016–2017. H5N6 virus was not detected in wild birds after March, but in late summer infected wild birds were found again. In this study, the complete genome sequences of poultry and wild bird viruses were determined to study their genetic relationship. Genetic analysis showed that the outbreaks in poultry were not the result of farm‐to‐farm transmissions, but rather resulted from separate introductions from wild birds. Wild birds infected with viruses related to the first outbreak in poultry were found at short distances from the farm, within a short time frame. However, no wild bird viruses related to outbreaks 2 and 3 were detected. The H5N6 virus isolated in summer shares a common ancestor with the virus detected in outbreak 1. This suggests long‐term circulation of H5N6 virus in the local wild bird population. In addition, the pathogenicity of H5N6 virus in ducks was determined, and compared to that of H5N8 viruses detected in 2014 and 2016. A similar high pathogenicity was measured for H5N6 and H5N8 group B viruses, suggesting that biological or ecological factors in the wild bird population may have affected the mortality rates during the H5N6 epidemic. These observations suggest different infection dynamics for the H5N6 and H5N8 group B viruses in the wild bird population.     

Emergence and adaptation of H3N2 canine influenza virus from avian influenza virus: An overlooked role of dogs in interspecies transmission

H3N2 canine influenza virus (CIV) originated from avian species and emerged in dogs in Asia around 2005 where it became enzootic before reaching the USA in 2015. To investigate the key aspects of the evolution of H3N2 CIV regarding its emergence and adaptation in the canine host, we conducted an extensive analysis of all publicly available H3N2 CIV sequences spanning a 10‐year period. We believe that H3N2 AIVs transferred to canines around 2002–2004. Furthermore, H3N2 CIVs could be divided into seven major clades with strong geographic clustering and some changed sites evidence of adaptive evolution. Most notably, the dN/dS of each H3N2 CIVs segment was higher than the correspondent of H3N2 AIVs and the U content of HA and NA was increasing over time, suggesting the idea that this avian‐origin virus may be gradually adapting to the host. Our results provide a framework to elucidate a general mechanism for emergence of novel influenza viruses.     

Bioaerosol and surface sampling for the surveillance of influenza A virus in swine

Influenza A virus in swine is of significant importance to human and veterinary public health. Environmental sampling techniques that prove practical would enhance surveillance for influenza viruses in swine. The primary objective of this study was to demonstrate the feasibility of bioaerosol and surface sampling for the detection of influenza virus in swine barns with a secondary objective of piloting a mobile application for data collection. Sampling was conducted at a large swine operation between July 2016 and August 2017. Swine oral fluids and surface swabs were collected from multiple rooms. Room‐level air samples were collected using four bioaerosol samplers: a low volume polytetrafluoroethylene (PTFE) filter sampler, the National Institute for Occupational Safety and Health's low volume cyclone sampler, a 2‐stage Andersen impactor and/or one high volume cyclonic sampler. Samples were analysed using quantitative RT‐PCR. Data and results were reported using a mobile data application. Eighty‐nine composite oral fluid samples, 70 surface swabs and 122 bioaerosol samples were analysed. Detection rates for influenza virus RNA in swine barn samples were 71.1% for oral fluids, 70.8% for surface swabs and 71.1% for the PTFE sampler. Analysis revealed a statistically significant relationship between the results of the PTFE sampler and the surface swabs with oral fluid results (p < 0.001 and p < 0.01 respectively). In addition, both the PTFE sampler (p < 0.01) and surface swabs (p = 0.03) significantly correlated with, and predicted oral fluid results. Bioaerosol sampling using PTFE samplers is an effective hands‐off approach for detecting influenza virus activity among swine. Further study is required for the implementation of this approach for surveillance and risk assessment of circulating influenza viruses of swine origin. In addition, mobile data collection stands to be an invaluable tool in the field by allowing secure, real‐time reporting of sample collection and results.     

Global genetic variation and transmission dynamics of H9N2 avian influenza virus

The H9N2 influenza viruses are extensively circulating in the poultry population, and variable genotypes can be generated through mutation, recombination and reassortment, which may be better adapted to infect a new host, resist drug treatment or escape immune pressure. The LPAI H9N2 viruses have the potential to evolve towards high levels of virulence in human. Some studies about the regional dispersal were reported, but global dissemination and the drivers of the virus are poorly understood, particularly at the genome scale. Here, we have analysed all eight gene segments of 168 H9N2 genomes sampled randomly aiming to provide a panoramic framework for better understanding the genesis and genetic variation of the viruses, and utilized phylogeography and spatial epidemiology approaches to uncover the effects of the genetic variation, predictors and spread of H9N2 viruses. We found that more frequent reassortment events involve segments PA , NP and NS , and 21 isolates have possible mosaic structure resulting from recombination events. Estimates of gene‐specific global dN /dS ratios showed that all genes were subject to purifying selection. However, a total of 13 sites were detected under positive selection by at least two of three methods, which located within segments HA , NA , M2, NS 1 and PA . Additionally, we inferred that NA segment has the highest rate of nucleotide substitution, and its tMRCA estimate is the youngest than the remaining segments’ inference. About the spatial history, air transportation of human was identified as the predominant driver of global viral migration using GLM analysis, and economic factors and geographical distance were the modest predictors. Higher migration rates were estimated between five pairs of regions (>0.01) indicating the frequent migration of the viruses between discrete geographical locations. Further, our Markov jumps analysis showed that viral migration is more frequent between Southern China and Northern China, and high rate of gene flow was observed between America and East Asia. Moreover, the America together with Southeast Asia acted as the primary hubs of global transmission, forming the trunk of evolutionary tree. These findings suggested a complex interaction between virus evolution, epidemiology and human behaviour.     

Poultry trading behaviours in Vietnamese live bird markets as risk factors for avian influenza infection in chickens

Vietnamese poultry are host to co‐circulating subtypes of avian influenza viruses, including H5N1 and H9N2, which pose a great risk to poultry productivity and to human health. AIVs circulate throughout the poultry trade network in Vietnam, with live bird markets being an integral component to this network. Traders at LBMs exhibit a variety of trading practices, which may influence the transmission of AIVs. We identified trading practices that impacted on AIV prevalence in chickens marketed in northern Vietnamese LBMs. We generated sequencing data for 31 H9N2 and two H5N6 viruses. Viruses isolated in the same LBM or from chickens sourced from the same province were genetically closer than viruses isolated in different LBMs or from chickens sourced in different provinces. The position of a vendor in the trading network impacted on their odds of having AIV‐infected chickens. Being a retailer and purchasing chickens from middlemen was associated with increased odds of infection, whereas odds decreased if vendors purchased chickens directly from large farms. Odds of infection were also higher for vendors having a greater volume of ducks unsold per day. These results indicate how the spread of AIVs is influenced by the structure of the live poultry trading network.     

Trade patterns facilitating highly pathogenic avian influenza virus dissemination in the free‐grazing layer duck system in Vietnam

Highly pathogenic avian influenza (HPAI ) viruses continue to threaten smallholder poultry producers in several South‐east Asian countries, including Vietnam. In particular, the free‐grazing duck system has been repeatedly highlighted as a major risk factor for HPAI outbreaks. Free‐grazing ducks, which scavenge on rice paddies after the harvest, account for a large proportion of the duck population in Vietnam and the wider South‐east Asian region. However, the structure and dynamics of the free‐grazing duck production from farm to consumption has not been described for Vietnam. In this study, we used a value chain approach to provide a complete picture of the actors involved in the production and marketing of free‐grazing duck eggs and spent layer ducks, as well as to investigate the governance structure of this food system. Group interviews and key informant interviews were conducted in two provinces located in the Mekong River Delta (MRD) and the Red River Delta (RRD). The results presented here highlight similarities and differences in farming and trade practices between the two provinces. The trade of spent layer ducks involved large volumes of live ducks being sent to China and Cambodia for consumption, generating a substantial risk of transboundary spread of pathogens, including HPAI viruses. We describe the major role of “duck yards”, which act as hubs in the northbound trade of spent layer ducks. These yards should be considered as essential links in the value chain of spent layer ducks when considering HPAI surveillance and control. The veterinary authorities are only marginally involved in the value chain activities, and their influence could be strengthened by increasing surveillance activities for instance in duck yards. Last, we discuss the dynamics of the duck value chain and further implications for future HPAI management policies.     

Genetic analysis identifies potential transmission of low pathogenic avian influenza viruses between poultry farms

Poultry can become infected with low pathogenic avian influenza (LPAI) viruses via (in)direct contact with infected wild birds or by transmission of the virus between farms. This study combines routinely collected surveillance data with genetic analysis to assess the contribution of between‐farm transmission to the overall incidence of LPAI virus infections in poultry. Over a 10‐year surveillance period, we identified 35 potential cases of between‐farm transmission in the Netherlands, of which 10 formed geographical clusters. A total of 21 LPAI viruses were isolated from nine potential between‐farm transmission cases, which were further studied by genetic and epidemiological analysis. Whole genome sequence analysis identified close genetic links between infected farms in seven cases. The presence of identical deletions in the neuraminidase stalk region and minority variants provided additional indications of between‐farm transmission. Spatiotemporal analysis demonstrated that genetically closely related viruses were detected within a median time interval of 8 days, and the median distance between the infected farms was significantly shorter compared to farms infected with genetically distinct viruses (6.3 versus 69.0 km; p < 0.05). The results further suggest that between‐farm transmission was not restricted to holdings of the same poultry type and not related to the housing system. Although separate introductions from the wild bird reservoir cannot be excluded, our study indicates that between‐farm transmission occurred in seven of nine virologically analysed cases. Based on these findings, it is likely that between‐farm transmission contributes considerably to the incidence of LPAI virus infections in poultry.     

Factors influencing chicken farmers' decisions to implement prevention and control measures to reduce avian influenza virus spread under endemic conditions

The ongoing circulation of Highly Pathogenic Avian Influenza (HPAI) H5N1 poses a threat to both poultry and public health. Adapting the constructs of the Health Belief Model (HBM) framework, we investigated perceptions of backyard, commercial broiler and layer chicken farmers to implement HPAI prevention and control measures in Bangladesh. Two cross‐sectional studies were conducted in 2016 and 2017 on 144 backyard, 106 broiler and 113 layer chicken farms. Using Structural Equation Modelling, we modelled the direct and indirect effects on farmers' perceptions on taking HPAI prevention and control actions. Our results indicate that farmers of different chicken production systems have different decision‐making processes. While perceived barriers to the implementation of prevention and control measures (e.g. wearing protective equipment when handling chickens) prevented both broiler and backyard farmers to adopt interventions, perceived benefits of measures (e.g. maintaining high biosecurity will reduce the risk of birds becoming sick) strongly influenced commercial farmers' decisions, but not backyard farmers' decisions. Information provided on HPAI through media, meetings or via information campaigns played an important role in farmers' decision‐making in all production systems. Outcomes of this research can be used to tailor advice on HPAI control and prevention to different poultry farming groups by accounting for specific factors influencing their decision‐making, instead of using one‐size‐fit‐all communication approach.