Use of Akaike information criteria for model selection and inference. An application to assess prevention of gastrointestinal parasitism and respiratory mortality of Guinean goats in Kolda,Senegal

A field experiment was carried out in Kolda (southern Senegal) from July 1986 to July 1988. Its goals were to: (1) describe the patterns of mortality of female Guinean goats by age, season and year; (2) assess preventive measures against respiratory diseases and gastrointestinal parasitism in reducing mortality; and (3) estimate the overall impact of these measures on survival to 1 year of age. Preventive measures for respiratory disease included vaccination against peste des petits ruminants (PPR) and pneumonic pasteurellosis (Pasteurella multocida types A and D). Control of gastrointestinal parasites was by deworming does with morantel (7.5 mg kg⁻¹, three times during the rainy season). The effects of vaccines and deworming were tested in a randomised factorial field experiment with villages being the experimental units. A total of 19 villages, 113 goat herds and 1458 goats were included in the study.

Generalised linear models of survival for five cohorts of goats (defined by five different birth seasons) used a binomial assumption for the response distribution and a complementary log–log link. Explanatory variables included age, season, year, vaccination, deworming and their interactions. A complex a priori model was built on the basis of previous epidemiological knowledge; a purposively selected set of simpler models was compared to this full model by the Akaike information criterion (AIC) and derived statistics. Inference on 1-year survival and treatment effects accounted for model-selection uncertainty. It was carried out with a bootstrap procedure and used information from the whole set of selected models.

Large variations in mortality by year and season were observed but no regular seasonal pattern was apparent. Mortality probabilities of kids in dewormed groups decreased quickly after birth, but remained elevated up to 9 months of age in the non-dewormed groups. Deworming lowered the risk of mortality. Vaccination alone was not protective (except during an observed outbreak of PPR).     

互助藏羊肺炎病原绵羊肺炎支原体的PCR检测与分析

青海省互助某羊场藏系绵羊发生肺炎疾病,为了快速准确诊断藏羊肺炎发病的致病病原微生物,及时防控和治疗,采集病死绵羊肺样品,利用PCR分子生物学方法进行鉴定与生物信息学分析。经过分子鉴定,此羊场引发肺病的病原是绵羊肺炎支原体(Mycoplasma ovipneumoniae, MO);测序结果显示样品中鉴定的为同一株病原,鉴定的菌株的16S rRNA基因与参考序列EU265779的同源性达到99.86%。同时遗传进化树显示,鉴定的菌株与GenBank中的绵羊肺炎支原体聚成一大支,其关系最近,在进化角度证实此次鉴定的确实为绵羊肺炎支原体。结果表明,此羊场引发肺炎疾病的病原是绵羊肺炎支原体,提示要对羊群进行相关的病原学研究和流行病学调查,为针对性地对细菌性病原进行对症治疗提供参考。     

菠萝皮发酵生产饲料蛋白优良菌种的筛选

以菠萝皮为原料,经烘干粉碎后添加一定辅料,采用10株不同的霉菌和酵母菌株进行单一菌种发酵试验,预筛选出产蛋白含量较高的3株霉菌和1株酵母菌;再将预筛选出的霉菌和酵母菌经过不同组合按一定的比例和接种量对菠萝皮渣进行混和菌种发酵。结果表明:采用绿色木霉(Trichodermaviride)和产朊假丝酵母(Candicau-tilis)按3:2的接种比例、5%的总接种量进行发酵,可使菠萝皮发酵产物的粗蛋白质含量和水洗蛋白含量显著提高,且发酵产物气味芳香,适口性好,可做动物蛋白饲料。     

尼帕病毒检测技术研究进展

尼帕病毒（Nipah virus, NiV）是一种人畜共患的高致病性病毒,人感染NiV后,死亡率接近40%;猪作为中间宿主,感染NiV后具有高发病率和高死亡率特点。近年来,NiV疫情在我国相邻的多个东南亚国家频繁出现,预示该病传入我国风险日益增高。本研究阐述了近年来NiV在血清学诊断和分子学诊断技术方面的研究进展,包括临床常用的传统技术,以及重组蛋白ELISA、Luminex、二代测序等新兴诊断方法,为临床样本中NiV的鉴定和监测方法更新换代提供参考,对监测NiV从国外的传入情况、防控猪群NiV疫情发生以及守护公共卫生安全具有重大意义。     

猪FSHβ亚基基因、ESR及ob基因分子遗传标记的检测方法

本文对影响猪繁殖性能和产肉性能的雌激素受体 (ESR)基因、促卵泡素 (FSH) β亚基基因和ob基因的检测方法进行了研究 ,对不同基因型的PCR反应条件和程序进行了改进 ,建立了一次PCR反应同时检测这 3个基因分子遗传标记的方法 ,结果与分别对 3个基因进行检测的结果完全相同     

Multilocus sequence typing as a tool for studying the molecular epidemiology and population structure of Brachyspira hyodysenteriae

The purpose of this study was to develop and apply a multilocus sequence typing (MLST) scheme to study the molecular epidemiology of Brachyspira hyodysenteriae, the aetiological agent of swine dysentery. Sequences of seven conserved genomic loci were examined in 111 B. hyodysenteriae strains. Fifty-eight of these previously had been analysed by multilocus enzyme electrophoresis (MLEE), and for some the results of pulsed field gel electrophoresis (PFGE), restriction endonuclease analysis (REA) and/or serotyping also were available. The discriminatory power of these methods was compared. The strains were divided into 67 sequence types (STs) and 46 amino acid types (AATs) by MLST. The Index of Association value was significantly different from zero, indication that the population was clonal. Eleven clonal complexes (Cc) comprising between 2 and 10 STs were recognised. A population snapshot based on AATs placed 77.5% of the isolates from 30 of the AATs into one major cluster. The founder type AAT9 included 13 strains from nine STs that were isolated in Australia, Sweden, Germany and Belgium, including one from a mallard. The MLST results were generally comparable to those produced by MLEE. The MLST system had a similar discriminatory power to PFGE, but was more discriminatory than REA, MLEE or serotyping. MLST data provided evidence for likely transmission of strains between farms, but also for the occurrence of temporal “micro-evolution” of strains on individual farms. Overall, the MLST system proved to be a useful new tool for investigating the molecular epidemiology and diversity of B. hyodysenteriae.     

单核苷酸多态性及其应用

单核苷酸多态性（single nucleotide polymorphisms,SNPs）是一种新的分子标记，是指基因组由于单个核苷酸的变异所产生的差异。由于其多态性高，便于自动操作等特点，在基因组、后基因组时代具有广泛的应用前景。本文对SNPs的概念、特点、分析方法及应用等方面做了简要的概述。     

Genotyping of Mycobacterium bovis by geographic location within Mexico

The spacer oligonucleotide typing (spoligotyping) method was used to differentiate 62 Mycobacterium bovis isolates obtained from tissues with macroscopic lesions typical of tuberculosis in dairy cattle from different regions of Mexico. Our purpose was to see if a strain from one region was genetically different from those of other regions (with the long-term aim of doing molecular trace back of isolates obtained in the laboratory). Results from the genetic analysis indicate that M. bovis isolates cannot be grouped by geographic location due to a wide range of genetic types involved in dairy cattle infections. Isolates even from the same herd showed different spoligotypes but some isolates from different region had similar genetic patterns. Genetic typing without epidemiologic information does not seem to be a plausible method to trace back animals to source of origin to detect and eliminate sources of infection.     

贵州省羊口疮病例分子生物学诊断

为了更好地鉴别诊断疑似羊口疮病例,采用PCR技术、分子克隆技术和生物信息技术对毕节地区羊口疮疑似病例进行实验室诊断。结果显示,从疑似病例组织病料中扩增出与预期大小相符的1137bp的B2L基因片断,且该基因核苷酸同源性与GenBank中已发表羊口疮病毒序列间的同源性为97．1％～99．1％。试验结果表明,该病例为羊口疮...