Estimating the Sensitivity and Specificity of Real‐Time Quantitative PCR of Fecal Samples for Diagnosis of Rhodococcus equi Pneumonia in Foals

Background

Real‐time, quantitative PCR (qPCR) methods for detecting Rhodococcus equi in feces have been developed as a noninvasive, rapid diagnostic test for R. equi pneumonia, but have not been evaluated in a large population of foals.

Objective

The objective of this study was to evaluate the clinical utility of fecal PCR as a diagnostic test for R. equi pneumonia in foals using receiver operating characteristic (ROC) methods.

Animals

186 foals born in 2011 at an R. equi‐endemic ranch in Texas.

Methods

Fecal samples were collected at the time of onset of clinical signs for pneumonic foals (n = 31). Foals with pneumonia were matched by age and birth date to healthy (n = 31) and subclinical (n = 124) control foals; fecal samples were collected from these controls. DNA was extracted from feces using commercial kits and concentration of virulent R. equi in feces was determined by qPCR.

Results

Concentration of R. equi in feces differed significantly (P < .05) among groups. The area under the ROC curve for fecal qPCR for diagnosis of R. equi pneumonia was 89% (95% CI, 83–99), with a sensitivity of 94% and specificity of 72%.

Conclusions and Clinical Importance

qPCR of feces can be useful as an alternative to tracheobronchial aspiration for the diagnosis of R. equi in foals with clinical signs of pneumonia. Caution should be used in extrapolating results of this study to other populations because fecal concentration of R. equi might vary by geographic location or management practices.     

Using mixed methods to investigate factors influencing reporting of livestock diseases: A case study among smallholders in Bolivia

Livestock disease surveillance is particularly challenging in resource-scarce settings, where disease events are often unreported. Surveillance performance is determined as much by the quantifiable biological attributes of the disease, as it is by motivations and barriers perceived by livestock keepers for disease reporting. Mixed methods designs, which integrate the collection, analysis and interpretation of qualitative and quantitative data in a single study, are increasingly used across different disciplines. These designs allow for a deeper exploration of the topic under investigation, than can be achieved by either approach alone.     

一株A型副鸡嗜血杆菌的分离鉴定

从山东省某蛋鸡场发病鸡群中分离到一株细菌,经培养特性观察、生化试验、V因子生长试验、致病性试验和PCR试验,证实分离菌为一株致病性副鸡嗜血杆菌,血清型鉴定该菌为A型。药物敏感性试验表明分离菌对头孢噻肟、头孢曲松、丁胺卡那霉素高度敏感,对硫酸新霉素、强力霉素中度敏感,对磺胺间甲氧嘧啶钠、环丙沙星、庆大霉素耐药。     

养殖大黄鱼溶藻酸弧菌病病原菌传染途径的研究

从养殖大黄鱼病鱼的肝脏和脾脏内分离、纯化到溶藻酸弧菌，经回归感染试验证实它是该病的致病菌。使用法国生物一梅里埃公司生产的自动细菌鉴定仪(ATB)进行细菌鉴定，该菌株的生理生化特性符合溶藻酸弧菌的特性。研究结果表明，养殖大黄鱼溶藻酸弧菌病病原菌传染途径，主要是从水经伤口传染到体内，在试验条件下传染率为60％。病原菌在30℃时生长很快，20℃时生长慢，10℃时基本不生长，对氟苯尼考、四环素和乙酰螺旋霉素等7种药物敏感。     

高致病性禽流感与天气条件分析

利用全国气象观测资料、NCEP／NCAR日平均再分析数据资料集和我国高致病性禽流感疫情资料,分析高致病性禽流感发生的时空特征以及与天气条件的关系。结果表明,我国高致病性禽流感全年可以发生,疫情的分布范围广,大部分地区都有出现。发生和传播与环境气象条件有关,季节性明显,冬季和秋季为主要发病季节。冬季禽流感发生前高空500hPa以槽为主,冷空气活动频繁。发生日基本在高压系统的控制之下,地面流场呈辐散状,风速稳定少变。     

番茄黄化曲叶病毒(TY)侵染性克隆接种鉴定方法研究

采用YEP1和YEP2培养基培养番茄黄化曲叶病毒侵染性克隆pBinPLUS-1.7A＋2β,并用固体菌落、液体菌菌液浓度OD600≈0.6、液体菌菌液浓度OD600≈1.0对感病番茄品种MM、中蔬4号、98-B1在4~6叶苗期进行接种处理。结果显示,2种液体培养基的液体菌菌液浓度为OD600≈0.6时接种处理发病率较高,并初步确立了无TY发病地区侵染性克隆接种鉴定方法。     

Does reduced MHC diversity decrease viability of vertebrate populations?

Loss of genetic variation may render populations more vulnerable to pathogens due to inbreeding depression and depletion of variation in genes responsible for immunity against parasites. Here we review the evidence for the significance of variation in genes of the Major Histocompatibility Complex (MHC) for conservation efforts. MHC molecules present pathogen-derived antigens to the effector cells of the immune system and thus trigger the adaptive immune response. Some MHC genes are the most variable functional genes in the vertebrate genome. Their variation is clearly of adaptive significance and there is considerable evidence that its maintenance is mainly due to balancing selection imposed by pathogens. However, while the evidence for selection shaping MHC variation on the historical timescale is compelling, a correlation between levels of MHC variation and variation at neutral loci is often observed, indicating that on a shorter timescale drift also substantially affects MHC, leading to depletion of MHC diversity. The evidence that the loss of MHC variation negatively affects population survival is so far equivocal and difficult to separate from effects of general inbreeding. Some species with depleted MHC variation seem to be particularly susceptible to infection, but other species thrive and expand following severe bottlenecks that have drastically limited their MHC variation. However, while the latter demonstrate that MHC variation is not always critical for population survival, these species may in fact represent rare examples of survival despite of the loss of MHC variation. There is clearly a compelling need for data that would disclose the possible consequences of MHC diversity for population viability. In particular, we need more data on the impact of MHC allelic richness on the abundance of parasites or prevalence of disease in populations, while controlling for the role of general inbreeding. Before such evidence accumulates, captive breeding programs and other conservation measures aimed at inbreeding avoidance should be favoured over those protecting only MHC variation, especially since inbreeding avoidance programs would usually conserve both types of genetic diversity simultaneously.     

表达传染性法氏囊病病毒VP2基因的重组鸡痘病毒的构建及其免疫保护性研究

以脂质体转染技术构建了表达鸡传染性法氏囊病病毒（ＩＢＤＶ）ＶＰ２基因的重组鸡痘病毒ＦＰＶ－ＶＰ２，该病毒在鸡胚成纤维细胞及鸡体内均能稳定产生子代病毒，经翅皮下５×１０５ＰＦＵ／羽免疫１日龄ＳＰＦ鸡，免疫后４周以１００ＬＤ５０／羽ＩＢＤＶ超强毒株Ｇ株攻毒，获得了５／６的保护，但不能有效预防临床发病及法氏囊受损萎缩。实验结果证明了ＶＰ２是ＩＢＤＶ的宿主保护性抗原，提示Ｔ细胞介导的免疫可能在ＩＢＤＶ的免疫中起着较为重要的作用。本研究为ＩＢＤＶ重组病毒疫苗研制进行了有益探索。     

禽副粘病毒2型(PMV-2)致病性的研究

7日龄SPF鸡经滴鼻、点眼感染PMV-2，可引起轻微的呼吸道症状，病理组织学观察可见气管粘液分泌亢进和少量的淋巴细胞浸润。PMV-2与传染性支气管炎（IBV）或鸡毒支原体（MG）协同感染比单纯感染这三种病原的任何一种均呈现更严重的呼吸道症状，病理组织变化呈气管纤毛部分或全部脱落，气管粘膜上皮细胞不同程度的变性、脱落。固有层和粘膜下层严重水肿，有大量淋巴细胞、巨噬细胞和异嗜细胞浸润。SPF雏鸡感染PMV-2后的不同时间检查病毒在鸡体内的分布规律，结果表明，PMV-2在法氏囊中大量分布；气管、肺、胸腺中有较多病毒；大脑、脾和肾脏只有少量病毒存在。上述实验结果揭示PMV-2感染SPF雏鸡致病性较弱，PMV-2在鸡呼吸道综合征中起一定作用。