The tissues samples of 343 spontaneous diseased ducks from 36 duck flocks were collected in Shandong,Jiangsu,Sichuan,Fujian and Guangdong,and the DNA was extracted to detect duck circovirus(DuCV) by hybridization and PCR.The results showed that the samples of the 5 provinces existed DuCV,and the individual positive ratio of DuCV was 81.63%(280/343) and the flock positive ratio of DuCV was 94.44%(34/36),indicating that the infection of DuCV exists wide-ranging in duck flocks of China.

Twenty strains of Riemerella anatipestifer(RA) were isolated and identified based on biochemical tests from suspected sick ducks with infectious serositis in Guangdong province and the results of animal experiment showed that the pathogenicity of the isolated RA strains was very high.The result of drug sensitivity test showed twenty RA strains had widely drug-resistance.According to two pairs of published primers and using whole bacteria cells as the template,the duplex PCR was established.The results showed that two fragments were amplified from all detected RA strains,while Escherichia coli,Pasteurella multocida,Salmonella and Staphylococcus aureus strains isolated from duck were negative results.Thus,the duplex PCR assay can be used to rapid identification and diagnosis of RA(infection).

The isolate GN52 of Riemerrella anatipestifer was passaged on the Martin Medium successively according to the optimum condition. The experiments included Gram staining, biochemical test, drug sensitivity test and animal experiments were carried out on the bacteria of 3rd, 11th, 21st, 31st, 41st, 51st and 61st generations. It indicated that the bacterial morphs, biochemical character, drug resistance of the strain had no obvious change, but the virulence showed a trend of reduction.

The duck circovirus (DuCV) infection in sick ducks from Fujian Province was investigated. The liver samples of 43 sick Muscovy ducks with infectious serositis were collected from 12 duck farms in Fujian Province. Based on the published sequences of DuCV, two primers were designed for the detection of DuCV and four pairs of primers were designed to amplify four overlapping fragments that cover the complete genome of DuCV. The specific PCR products were amplified from positive samples. The fragments were then cloned into pMD18-T vector and sequenced, and the full length genomic sequence of the FJ0601 isolate of DuCV was obtained. PCR analysis showed that the proportion of ducks which were positive for circovirus was 79% and 10 out of the 12 farms were positive. Sequence analysis showed that the complete genome of DuCV-FJ0601 was 1988 bp and possessed features common to the family Circoviridae which included a stem-loop structure and the Rep protein motifs. Homology analysis showed that FJ0601 isolate of DuCV had 97.3%∼97.5% nucleotide sequence identity to all the four Taiwan isolates (TC1/2002, TC2/2002, TC3/2002, TC4/2002), 82.9% identity to the America (33753-52) isolate and 82.3% identity to the Germany isolate. Phylogenetic analysis with Clustal W, however, showed that FJ0601 isolate of DuCV was on a common branch with Taiwan isolates, and Germany and America isolates belonged to the other branch.

In order to analyze sequences of OmpA of Chinese strains of Riemerella anatipestifer(RA),according to outer membrane protein A(OmpA) gene sequences from R.anatipestifer strains in the GenBank,a pair of specific primers was designed.Eight R.anatipestifer strains from Fujian,Guangdong and Shandong were amplified in the whole open reading frame(ORF) by PCR and then cloned and sequenced.The comparative analysis of the sequences with twenty-six R.anatipestifer strains in GenBank indicated all OmpA gene had a long complete ORF composed of 1164 nucleotides which encoded a protein of 387 amino acids,and all initiation codon were ATG and end codon were TAA.The sequence of OmpA were relatively conservative which identity was 88.2%～100% and the identity of the amino acids was 88.95%~100%.The results showed that the sequence of OmpA relatively conservative and the identity of the nucleotide and amino acid had no positive relation with the isolate serotype,the time and location of isolation.

<正>鸭传染性浆膜炎是由鸭疫里默氏杆菌(Riemerella anatipestifer,RA)引起的家鸭的一种慢性或急性败血性接触传染性疾病,又称新鸭病(New duck syndrome),鸭败血症(Duck septicemia),鸭疫综合症(Anatipestifer syndrome),鸭疫败血症(Anatipestifer septicemia)。主要侵害2~7周龄雏鸭,也可侵害雏鹅、雏火鸡以及野鸡等多种雏禽,以纤维素性心包炎、肝周炎、气囊炎、干酪性输卵管炎和脑膜炎等为病变特征,广泛分布于世界上各养鸭国家和地区,是目前造成养鸭业经济损失的主要传染病之一。