| Summary: | 博士 === 國立宜蘭大學 === 生物技術與動物科學系動物科學碩士班 === 107 === Nosema ceranae is a fungal disease commonly found in honey bees and it is origined from A. cerana then transferred its host to A. mellifera. The sacbrood disease happens to be the opposite. It is found in A. mellifera but its damage to the A. cerana colonies is more serious. This study is based on these two most common pathogens, N. ceranae and the most serious destruction in A. cerana colonies since 2016 in Taiwan, Apis cerana sacbrood virus (AcSBV), to confirm their pathogenicity and their prevalence in Taiwan.
In the study, the prevalence rate of N. ceranae from September 2013 to August 2014 was found the peaks of N. ceranae spore inteneity appeared in February and March in A. mellifera colony but no existence in A. cerana. The real-time polymerase chain reaction (RT-PCR) was used to detect the Nosema sr22 gene expression in the honey bees, and the average prevalence rate was above 40%. The survival rate was no significant decrease in A. mellifera larvae infected with N. ceranae but the emergence rate of adult bees decreased from 88.5% to 69.4% and the average survival days decreased from 20.9 to 19.3 days. Further examination of spore intensity changes in midgut revealed that the peaks of mature spores were between the 11th and 15th day post infection, when the peak of sr22 gene expression at the 15th day post infection. In addition, the 10th dpi of N. ceranae, the average proboscis extension reflex rate decreased from 80.83% to 58.33%, and the homing rates were decreased significantly at the 3rd, 7th, 10th and 14th dpi.
This study also used the gene fragment of AcSBV located on VP1 section to investigate the prevalence of AcSBV in northern Taiwan, providing a survey record from January 2017 to April 2019. Investigated 28 plots, including A. cerana, A. mellifera apiaries as well as a few wilderness groups. The results showed that the prevalence of AcSBV increased in 2017, but showed a downward trend in 2018 and 2019. There were two cross-infection period in May-July and August-September of 2017 happened between A. cerana and A. mellifera colonies, and after August 2018, the virus had formed a synchronization between the two bee species. Secondly, it can be found that the prevalences of AcSBV were satble in which A. cerana single-cultured apiaries, indicating that AcSBV had stably developed in A. cerana colonies. According to the phylogenetic analysis, the AcSBVs detected in this study were all grouped together, and the closest isolate belonged to the isolates from Fuzhou, China. There was also one specific-primer(SP-primer) set designed in this study, which could distinguish AcSBV and Apis mellifera scbrood virus(AmSBV) by RT-PCR. At the same time, the samples of 2019 were tested and the results showed that SP-primer had 20% more sensitive detection rate than the previously used CSBV-VP1 gene.
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