从广西蚕区分离的家蚕质型多角体病毒生物学特征研究

Biological characteristics of Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) isolated from the sericultural region of Guangxi

摘要:

【背景】家蚕中肠型脓病是一种传染性强、危害大的病毒病，其病原为家蚕质型多角体病毒（Bombyx mori cytoplasmic polyhedrosis virus，BmCPV），该病原抗逆性强、宿主域广，防控难度大。【目的】调查广西蚕区家蚕中肠型脓病发生情况，并研究家蚕质型多角体病毒的感染性、形态特征和分子鉴定，为养蚕生产中有效防控该病提供参考依据。【方法】通过外观和解剖观察病症与显微镜检验相结合，调查养蚕生产家蚕中肠型脓病的发生率；采用生物试验方法测定多角体病毒对家蚕的半数感染浓度（IC₅₀）；利用光学显微镜和扫描电镜观察多角体病毒的外部形态，利用透射电子显微镜观察多角体病毒的内部结构；采用PCR扩增和测序进行分子鉴定。【结果】广西蚕区家蚕中肠型脓病普遍存在，金城江蚕区和东兰蚕区的家蚕中肠型脓病平均发生率分别为6.06%和13.02%，最高发生率达到30.41%；分离获得2株BmCPV病原（暂命名为BmCPV-J和BmCPV-D），它们的半数感染浓度（IC₅₀）分别为4.88×10³ PIBs/mL和1.63×10⁴ PIBs/mL，都具有很强的致病性；2株BmCPV的形态均为六角形多角体，大小有差异，多角体直径为1.0-3.4 μm；从2株BmCPV内部结构观察到球形病毒粒子，直径为30-50 nm，有刺状突起；可以扩增出BmCPV-J和BmCPV-D的RNA复制酶基因目的片段，BmCPV-J的目的片段序列与BmCPV参考株一致，而BmCPV-D的目的片段序列与参考株有2个碱基的差异。【结论】广西蚕区家蚕中肠型脓病危害严重，该病病原感染力强、分布广，多角体病毒具有典型的质型多角体病毒特征，属于家蚕质型多角体病毒。研究结果为养蚕生产中有效防控家蚕中肠型脓病提供重要依据。

Abstract:

[Background] Silkworm (Bombyx mori) midgut polyhedrosis is a highly infectious and harmful viral disease caused by B. mori cytoplasmic polyhedrosis virus (BmCPV). Which virus has strong resistance, a wide host range, and is difficult to control and prevent. [Objective] To investigate the occurrence of silkworm midgut polyhedrosis in the sericultural region of Guangxi and study the pathogenicity, morphological characteristics, and molecular information of BmCPV, so as to provide a basis for the effective control of silkworm midgut polyhedrosis. [Methods] The anatomical and microscopic examinations of the diseased silkworm were combined to reveal the incidence of silkworm midgut polyhedrosis, and the median infectious concentration (IC₅₀) of BmCPV on silkworm was investigated via biological tests. The external morphology of BmCPVwas observed by optical microscopy and scanning electron microscopy, and the internal structure by transmission electron microscopy. PCR amplification and sequencing were employed to identify the BmCPV. [Results] Silkworm midgut polyhedrosis was prevalent in the sericultural region of Guangxi, with the incidence rate of 6.06% and 13.02% in Jinchengjiang and Donglan, respectively, and the highest incidence of 30.41%. Two BmCPV strains, BmCPV-J and BmCPV-D, were isolated from the diseased silkworm in the two sericultural regions, with the IC₅₀ of 4.88×10³ PIBs/mL and 1.63×10⁴ PIBs/mL, respectively, which indicated strong pathogenicity. BmCPV-J and BmCPV-D were hexagonal polyhedra with the diameters of 1.0-3.4 μm, differences in size between polyhedra, the spherical virion diameters of 30-50 nm, and spiny protuberances. PCR was conducted with the primers designed based on the RNA replicase gene of BmCPV. The fragment of BmCPV-J was identical with that of BmCPV reference strain, while that of BmCPV-D had two base differences. [Conclusion] Silkworm midgut polyhedrosis is a serious disease in the sericultural region of Guangxi, and its pathogen has strong infectivity and wide distribution. BmCPV-J and BmCPV-D with typical characteristics of CPV which belong to BmCPV. The results provide an important basis for the effective control of silkworm midgut polyhedrosis.