Study On Bombys Mori Blood Type Of Purulence Disease And Biological Medicament Preventing The Disease In Guangxi

Bombyx mori blood type of purulence disease, caused by the pathogen of B. mori nucleopolyhedrovirus (BmNPV), is also known as the silkworm nuclear polyhedrosis disease with the characteristics of strong infectivity and urgent high incidence. It is this disease that greatly obstructs the development of sericulture in Guangxi province at present.The silkworms species used in the research was Liangguang No.2 which was commonly raised in summer and autumn in the province. The research was carried out by doing a series of experiments in laboratory and production investigation. The research aspects included the molecular morphological structure of the polyhedra inclusion body (PIB) and virus particle of BmNPV, the pathogenicity of BmNPV and the nucleotide sequences of three primary structure protein genes which were related to its pathogenicity, the preparation of chicken immune egg yolk antibody, the preventing effects of immune egg yolk antibody or Nalidixic acid against BmNPV respectively and the united preventing effects of complex medicament which comprised of chicken immune egg yolk antibody, Nalidixic acid and BmNPV bacterin eactivated with formaldehyde. The main results of this research were summarized as follows:1. Bombyx mori nucleopolyhedrovirus was propagated in silkworms alive and purified by using different reagents. The photographs of the polyhedron and the virus particle were obtained by using optical microscope and scanning electronic microscope.2. Three main structural protein genes such as gp64, polyhedrin and p10 gene were cloned and sequenced respectively in order to compare them with the gene sequences from other baculovirues of the same family individually. According to the results, it showed a great homology between Guangxi strain and Guangzhou strain in p10 gene of BmNPV which was high conserved, while it also showed there were some differences between BmNPV and other NPV in polyhedrin gene sequence. The preliminary research results on the molecular epidemiology will lay a theoretical foundation for the effective prevention and treatment on the disease.3. The half lethal concentration (LC₅₀) of BmNPV from Guangxi and its correlation with the instar period of the larva was identified. It showed that the younger of larves were more susceptible with the virus. And investigation on the characteristic of the virus spreading in the rearing bed made clear that there was a significant correlation between the rear density, the different proportion of diseased silkworms mingled into the healthy ones and the ratio of infection. 4. The immune yolk which contained the antibody against the antigen was obtained from the hens immunized with the antigen of BmNPV. There were some good effects on preventing the larva against beening attacked by the virus when using the immune complex biological medicament, comprised of immune yolk antibody solution only or combined with nalidixic acid and BmNPV bacterin eactivated with formaldehyde.