高致病性猪繁殖与呼吸综合征病毒株JXA1反向遗传平台的构建

【目的】为高致病性猪繁殖与呼吸综合征病毒(Highly pathogenic porcine reproductive and respiratory syndrome virus,HP-PRRSV)的结构功能和致病机理的研究奠定基础。【方法】运用反向遗传技术将HP-PRRSV JXA1株的全基因组分段克隆至改造过的低拷贝载体pOKq上,并在病毒基因组两端分别添加CMV启动子和BGH终止信号肽以及在病毒全基因组第510位核苷酸突变引入Fse I酶切位点,作为遗传标记位点。采取基于DNA-launched途径进行病毒拯救,并对拯救的病毒进行生物学特性分析。【结果】构建的PRRSV JXA1毒株的全长cDNA克隆具有感染性;成功拯救了病毒,命名为rJXA1;成功引入了拯救病毒的遗传标记;拯救病毒与亲本病毒的生长曲线相似,二者达到最高滴度的时间均为感染后72 h。【结论】成功构建了JXA1株反向遗传平台,为进一步研究HP-PRRSV的致病机理、基因功能以及新型疫苗研发奠定了基础。     

Impact of farm management on expression of early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) on penaeid shrimp farms in Thailand

Asian shrimp farming industry has experienced massive production losses due to a disease caused by toxins of Vibrio bacteria, known as early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) for the last 5 years. The disease can cause up to 100% cumulative pond mortality within a week. The objective of this study was to identify factors associated with AHPND occurrence on shrimp farms. A case–control study was carried out on shrimp farms in four provinces of Thailand. Factors related to farm characteristics, farm management, pond and water preparation, feed management, post‐larvae (PL) shrimp and stock management were evaluated. Multivariable logistic regression analysis identified factors affecting AHPND occurrence at the pond level. Chlorine treatment, reservoir availability, use of predator fish in the water preparation, culture of multiple shrimp species in one farm and increased PL stocking density contributed to an increased risk of AHPND infection, while delayed first day of feeding, polyculture and water ageing were likely to promote outbreak protection. Additionally, the source of PL was found to be associated with AHPND occurrence in shrimp ponds, which requires further study at the hatchery level. Identification of these factors will facilitate the development of effective control strategies for AHPND on shrimp farms.     

Changes in the gut microbiome of the Chinese mitten crab (Eriocheir sinensis) in response to White spot syndrome virus (WSSV) infection

Intestinal microorganisms play important roles in maintaining host health, but their functions in aquatic animal hosts have yet to be fully elucidated. The Chinese mitten crab, Eriocheir sinensis, is one such example. We attempted to identify the shift of gut microbiota that occurred in response to infection of white spot syndrome virus (WSSV), an emerging viral pathogen in the crab aquaculture industry. The microbiota may exert some control over aspects of the viral pathogenesis. We investigated the changes in composition and structure of the crab gut microbiome during various WSSV infection stages of 6 h post‐infection (hpi) and 48 hpi, using a 16S rRNA approach on the MiSeq Illumina sequencing platform. Four phyla (Firmicutes, Proteobacteria, Tenericutes and Bacteroidetes) were most dominant in the gut of E. sinensis regardless of the WSSV infection stages. However, further analysis revealed that over 12 bacterial phyla, 44 orders and 68 families were significantly different in abundance at various states of WSSV infection. Several intriguing aspects of E. sinensis gut bacteria that had not been previously reported were also uncovered, such as class Mollicutes was dominant here, but absent in crabs from Yangtze River estuary and Chongming Islands. Overall, this study provided the first evidence that changes in gut microbiome were closely associated with the severity of WSSV infection and that indicator taxa could be used to evaluate the crab health status.     

In vitro and in vivo selection of probiotic purple nonsulphur bacteria with an ability to inhibit shrimp pathogens: acute hepatopancreatic necrosis disease‐causing Vibrio parahaemolyticus and other vibrios

Shrimp cultivation has been faced with huge losses in productivity caused by infectious shrimp pathogenic vibrios, especially Vibrio parahaemolyticus that causes acute hepatopancreatic necrosis disease (AHPND). Hence, purple nonsulphur bacteria (PNSB) were isolated from shrimp ponds for investigating their abilities to control shrimp pathogenic Vibrio spp. and their use as probiotics for sustainable shrimp cultivation. Based on their probiotic properties, strains S3W10 and SS15 were selected because of their strong abilities to produce amylase, gelatinase and vitamin B12. However, only three PNSB strains (SS15, TKW17 and STW181) strongly inhibited V. harveyi_KSAAHRC and V. vulnificus_KSAAHRC including V. parahaemolyticusAHPND strains by secreting antivibrio compounds. Four selected PNSB also grew in the presence of pancreatic enzymes, and they were identified as Rhodobacter sphaeroides for strains S3W10, SS15 and TKW17 and Afifella marina for strain STW181. The effects of a mixed culture were also investigated as follows: T1 (S3W10 + SS15), T2 (S3W10 + TKW17) and T3 (S3W10 + STW181) on postlarval white shrimp (Litopenaeus vannamei) for 60 days by comparison with a control. All three probiotic PNSB sets significantly improved the digestive enzyme activities and shrimp growth with their proliferation in shrimp gastrointestinal tract although the shrimp survival was not significantly different. They also significantly reduced the cumulative mortality of shrimp exposed to a virulent AHPND strain (V. parahaemolyticusSR2). This is the first to conclude that selected probiotic PNSB strains have great potential to be used for shrimp cultivation to control vibrios including AHPND strains.     

新疆褐牛应激综合症的防控

新疆褐牛是新疆养牛业的主导品种。随着社会经济的发展和养牛新技术的推广,在新疆褐牛养殖过程中,新疆褐牛的推广力度和养殖水平也逐步提高,新疆褐牛架子牛、育肥牛、种公牛及生产母牛异地调运频繁;同时为提高养殖效益,新疆褐牛断奶犊牛月龄逐步提前到4月龄;在养殖生产过程中,常常发生运输应激综合症和早期断奶应激症。本文通过探讨新疆褐牛运输综合症发生病因、症状和早期断奶犊牛应激表现,提出防控应对措施,以期为广大新疆褐牛养殖户在牛只调运和早期断奶技术上提供参考。     

蛋鸡脂肪肝综合征模型的建立

试验旨在建立蛋鸡脂肪肝综合征病理模型。选取5日龄的海兰褐蛋鸡公雏280只，随机分为对照组（基础日粮组）和3个模型组（A、B、C组），试验第1~10天给模型组饲喂不同配比的高脂饲料，第11~20天饲喂常规基础日粮，每天观察并记录试验鸡精神状态、外观体征、饮水量和食欲情况，试验第0、10、20天从各组随机抽取15只鸡进行翅静脉采血并剖取肝脏和腹脂，测定肝脏系数、肝脂率、腹脂率，血清总胆固醇（TC）、甘油三酯（TG）、谷丙转氨酶（ALT）和谷草转氨酶（AST）水平。结果显示，试验第10天，3个模型组剖检时可见腹腔和肠系膜有大量的脂肪沉积，肝脏系数、肝脂率和腹脂率，以及血清中总胆固醇、甘油三酯、谷丙转氨酶和谷草转氨酶指标均符合鸡脂肪肝综合征模型的诊断标准；试验第20天，模型A、B组谷丙转氨酶和谷草转氨酶水平有所恢复，其他指标仍高于对照组，而模型C组的临床症状和各项检测指标仍符合鸡脂肪肝综合征模型的诊断标准。因此采用连续饲喂高脂饲料C（74.5%基础日粮、6%胆固醇、14%猪油、5%蔗糖、0.5%丙基硫氧嘧啶）可成功建立蛋鸡脂肪肝综合征模型。     

猪皮炎肾病综合征诊断与防治

猪皮炎肾病综合症是由圆环病毒二型感染引起的一种以猪皮肤表面出现红疹、丘疹、结痂或坏死,肾脏严重肿大为主要临床特征的常见传染性疾病。皮炎肾病综合症主要危害生长猪和育肥猪。受病毒感染后,患病猪表现为生长发育不良,免疫功能受到严重抑制,易继发感染其他传染性疾病,表现出复杂的临床症状,给生猪养殖业造成严重损失和危害。防范疾病的发生流行,需要掌握猪皮炎肾病综合症的具体流行特点、临床表现,并采取针对有效措施进行诊断,然后构建有效的防控措施,短时间内控制病情,避免损失进一步加大。该文主要论述猪皮炎肾病综合症的流行特点、临床症状、病理变化、诊断方法和防治措施。     

A Lymphoid Organ Specific Anti-Lipopolysaccharide Factor from Litopenaeus vannamei Exhibits Strong Antimicrobial Activities

Different shrimp species are known to possess apparent distinct resistance to different pathogens in aquaculture. However, the molecular mechanism underlying this finding still remains unknown. One kind of important antimicrobial peptides, anti-lipopolysaccharide factors (ALF), exhibit broad-spectrum antimicrobial activities. Here, we reported a newly identified ALF from the shrimp Litopenaeus vannamei and compared the immune function with its counterpart in the shrimp Fenneropenaeus chinensis. The ALF, designated as LvALF8, was specifically expressed in the lymphoid organ of L. vannamei. The expression level of LvALF8 was apparently changed after white spot syndrome virus (WSSV) or Vibrio parahaemolyticus challenges. The synthetic LBD peptide of LvALF8 (LvALF8-LBD) showed strong antibacterial activities against most tested Gram-negative and Gram-positive bacteria. LvALF8-LBD could also inhibit the in vivo propagation of WSSV similar as FcALF8-LBD, the LBD of LvALF8 counterpart in F. chinensis. However, LvALF8-LBD and FcALF8-LBD exhibited apparently different antibacterial activity against V. parahaemolyticus, the main pathogen causing acute hepatopancreatic necrosis disease (AHPND) of affected shrimp. A structural analysis showed that the positive net charge and amphipathicity characteristics of LvALF8-LBD peptide were speculated as two important components for its enhanced antimicrobial activity compared to those of FcALF8-LBD. These new findings may not only provide some evidence to explain the distinct disease resistance among different shrimp species, but also lay out new research ground for the testing and development of LBD-originated antimicrobial peptides to control of shrimp diseases.