Viral agents associated with poult enteritis and mortality syndrome: the role of a small round virus and a turkey coronavirus

Intestinal samples from turkey poults affected with poult enteritis and mortality syndrome (PEMS) were examined for viruses by immune electron microscopy and double-stranded RNA virus genome electropherotyping. Turkey coronavirus (TCV), avian rotaviruses, reovirus, and a yet undefined small round virus (SRV) were detected. The SRV and TCV were isolated and propagated in turkey embryos. Challenge of specific-pathogen-free turkey poults with SRV, TCV, or both resulted in mortality and clinical responses similar to those of natural PEMS. Our experiments indicate that SRV and TCV are possibly important agents in the etiology of PEMS and the combination of these infections might result in outbreaks with high mortality. The severity of clinical signs and mortality of PEMS are postulated to be partly related to the virus agents involved in individual outbreaks.     

Performance of a foot-and-mouth disease virus reverse transcription-polymerase chain reaction with amplification controls between three real-time instruments.

The foot-and-mouth disease virus (FMDV) is a member of the picornavirus family, possessing an 8-kb single-stranded RNA genome of positive polarity. It is highly contagious among several livestock species and can lead to severe economic consequences, as evidenced by the UK outbreak in 2001. The usage of real-time polymerase chain reaction has facilitated rapid detection of FMDV. Several real-time PCR instruments are available with various capabilities, such as portability and high sample volume analysis. Primers and a dual-labeled TaqMan probe were optimized to detect a single, highly conserved 88-bp segment of the FMDV 3D (RNA polymerase) gene. To increase the confidence of the RT-PCR result, a positive amplification control was synthesized to detect potential false-positive results due to contamination if a wild-type virus is used as positive control. In addition, a preventative measure against false-negative results was developed in which endogenous beta actin mRNA is coamplified by RT-PCR. Assay performance was compared on the LightCycler1.2 (Roche), the SmartCyclerII (Cepheid), and the SDS 7900HT (ABI). These assays successfully identified the FMDV genome and beta actin mRNA from several sources of infected nasal and oral swabs, as well as probang samples.     

检测CSFV、JEV、PRRSV三种RNA病毒多重RT-PCR方法的建立

猪瘟病毒(CSFV)、流行性乙型脑炎病毒(JEV)和猪繁殖与呼吸综合征病毒(PRRSV)是引起严重的种猪繁殖障碍的病原,而且经常混合感染,及时准确诊断是防治的前提。根据GenBank发表序列选取3对引物建立检测CSFV、JEV和PRRSV病毒的多重RT-PCR方法,扩增产物分别为508 bp、380 bp、263 bp。经与IDEXX商品化的检测CSW抗原试剂盒比较,二者的符合率为96.7%;扩增JEV和PRRSV PCR产物分别经EcoR V和Sau3A I酶切得到预期的片段。建立的多重RT-PCR检测JEV、PRRSV和CSFV敏感度分别为12.5个TCID_(50)、10个TCID_(50)和10~(-3)ng总RNA。结果表明该多重RT-PCR方法具有很好的特异性和敏感性,可用于临床三种病毒核酸的检测。