To understand the prevalence, coinfection with other viruses, underlying genetic evolution, recombination, and molecular biological characteristics of goose circovirus (GoCV) in Guangdong, China, from December 2019 to August 2020, 310 tissue samples of geese showing stunted growth and feather disorder syndrome were collected from this region and analyzed. GoCV, Tembusu virus, waterfowl paramyxovirus, avian influenza virus, fowl adenovirus type 4, and duck plague virus were detected with PCR or real-time PCR. Thirty-one complete GoCV viral genomes were obtained from 164 PCRverified GoCV nucleotide-positive samples and subjected to phylogenetic analysis, gene recombination analysis, and genome secondary structure prediction. The results showed that more than half of the samples were GoCV positive, and 31.1% of the GoCV- positive samples were from coinfections with at least one of the other viruses. The phylogenetic analysis showed that the GoCVs could be divided into three genome types. The genes of most main epidemic strains now circulating in Guangdong belonged to the Ia subtype, and some strains gradually formed a new Ib subtype. The secondary structure of the viral genome was similar to that of other known circoviruses. Furthermore, B cell linear epitope prediction and protein structure homology modeling of the viral capsid protein were performed based on the viral amino acid sequences. The results showed that the spatial structure of the capsid protein of the 31 sequenced strains was similar to that of duck circovirus and consisted of two b-sandwich conformations. A total of five B cell linear epitopes were predicted, and four of them were mapped on the predicted model of the capsid protein of GoCVs. This report provides a reference for the epidemiology of GoCV in Guangdong, understanding the elemental composition of the virus genes and proteins, selecting representative vaccine strains, constructing targeted immune preparations for GoCV, and strengthening prevention and control of the disease.

2019～2020年从广东肇庆地区的部份鹅场中收集到12份疑似小鹅瘟病例,对疑似小鹅瘟病例进行病原核酸鉴定,对阳性病例进行病毒分离和VP1基因的序列扩增和遗传进化分析.结果表明,12份疑似小鹅瘟病例中,共检测到7份阳性样品,阳性检测率为58.3％.从阳性病例样本中分离获得7株小鹅瘟病毒毒株,其中1株与Ⅰa亚群毒株核苷酸序列相似性高达99.1％～99.3％,另6株则聚类形成此前未报道过的新亚群,本文将其命名为Ⅰf亚群.本研究结果进一步完善了我国广东地区小鹅瘟的流行病学信息,为本地区小鹅瘟病毒的流行病学调查及该病的综合防控奠定理论基础.

为了解鸭疫里默氏杆菌在广东佛山地区养殖水禽群中的流行、耐药和对雏鸭的致病力等情况,本研究从该地区6个鹅场、9个鸭场共采集130份有疑似传染性浆膜炎临床症状的肝、脑样品,经分离、纯化和鉴定获得15株鸭疫里默氏杆菌.对新分离株的16S rRNA进行测序及遗传进化分析,并进一步检测新分离株的耐药性和对雏鸭的致病性.结果表明:所有分离株16S rRNA遗传进化上均与鸭疫里默氏杆菌血清Ⅰ型参考株TRa1处于同一进化分支;15株分离菌对阿莫西林、青霉素、链霉素等8种常用抗生素表现多重耐药,而对头孢唑啉、大观霉素和氟苯尼考敏感.选取一株鸭源菌株(Y15)进行雏鸭致病性试验,感染组雏鸭死亡率为60％,病死鸭表现典型鸭疫里默氏杆菌病临床症状.本研究结果为进一步了解鸭疫里默氏杆菌在广东地区水禽群中的流行、耐药性以及致病力情况提供参考依据.

随着南方进入梅雨季节,许多肉鹅养殖场由于对饲料霉变的不重视,而导致的饲料发霉,霉变情况越来越严重,随之而来的是鹅病的多发,尤其与免疫抑制类疾病相辅相成,最终使用药成本的增加和养殖效益的降低.因此生产管理者应该在管理上杜绝饲料或者原料霉变的发生,重视对防霉脱毒的处理,从而避免或者降低饲料霉菌毒素而引起的中毒.

肉用种鸡场在华南地区盛夏季节鸡群死淘率居高不下,日死淘率达到0.1～0.5％,月累计死淘率达到3～15％,其主要原因包括以下四方面:选育不良导致的脱肛,环境温度控制不良导致的中暑,夏季季节性疾病的频发和继续性疾病的伴随.本文简述了造成华南地区肉用种鸡场盛夏季节死淘率增高的原因、发病特点、诊断要点与防控的基本建议,为有效控制华南地区种鸡场盛夏季节鸡群死淘提供一定的帮助.