Effect Of Chinese Sacbrood Virus (CSBV) And Migratory Beekeeping On Honeybee Health

Honeybees are important pollinators for global agricultural production and economic development.However,in recent years,a decline in bee populations has been observed.This phenomenon has brought great losses to agricultural production.The problems of bee health have gradually attracted widespread attention.Therefore,this article mainly studied the effect of Chinese sacbrood virus(CSBV)and migratory beekeeping on honeybee(Apis mellifera and Apis cerana)health.The principle results are as follows:(1)A survey of honey bee viruses and co-infection of Apis cerana cerana in different areasSamples collected in 5 provinces were tested for presence of six common honey bee viruses.The results showed that all the six viruses were detected.However,the infection rate of different viruses was different.Except for the ABPV,the infection rate of other viruses in diseased bees was higher than healthy bees.Analysis of co-infection of virus showed that the infection rates of virus in diseased bee was higher than healthy bee.(2)Transmission routes of CSBV in hostsCSBV was detected in different stages of worker samples,the ovary and spermatheca of queens,the penis and sperm of drones,the feces of queens,brood food,honey and royal jelly from nine colonies that exhibited obvious sacbrood symptoms.This indicates a horizontal transmission route of CSBV in the colonies studied.From the infection status of CSBV in some colonies,We concluded that if ovaries or spermatheca contain virus,the eggs were also could be detected.These results indicate that CSBV is also transmitted from the queen to offspring by vertical transmission.In addition,CSBV was found in Galleria mellonella from one colony,This provides evidence that supports the fact that Galleria mellonella can act as a carrier of bee viruses,promoting the spread of the virus within the colony.(3)Effects of CSBV on Transcriptome of larva(Apis cerana cerana)By high throughput RNA sequencing technology of infected larvae and healthy larvae,Compared with GO,there was a significant difference in 5815 gene between the infected group and the healthy group.According to the data of the healthy group,6471 genes were up-regulated and 4983 genes were down-regulated in the infected group.A total of 2185 different genes between infected larvae and healthy larvae can be enriched in 273 metabolic pathways,of which 32 signaling pathways are significantly enriched,including immune-related signaling pathways.(4)The dynamic variation of immune related gene expression in Apis cerana cerana with Chinese sacbrood Virus infectionUsing quantitative PCR,we examined expression levels of honeybee worker immune genes at different developmental stages(egg,1st,3rd and 5th instar larvae,pupae of five stages,newly emerged bees and forager bees).Expression levels of these immune genes were compared between virus-infected and uninfected honeybees.The results showed that the mRNA of four immune genes were detected in all development stages and their dynamic changes were similar.The expression levels of genes in egg and larvae of early and medium period(1st and 3th instar larvae)were very low,in larvae later period(5th instar larvae)significantly higher than those in early development stages.The genes expression gradually decreased when honey bees entered into pupal stage,and then stabilized in whole pupal period and newly emerged stage.In Forager stages,the expression level was significantly highest among all development stages.Four Antimicrobial peptides had a significant difference or extreme significant difference between unhealthy bees and healthy bees.For four genes expression changes in different growth stages,the immune gene expression levels in infection bees were higher than healthy bees,and the two groups had the biggest differences at 5th instar larvae stages.From the results presented in this study,we confirm that Chinese sacbrood virus infection induces host immunopotentiation.(5)The variation of Pathogens,Parasites and symbionts in Migratory honeybees(Apis mellifera ligustica)The results showed that IAPV,BQCV,DWV and microsporidia are prevalent in the migratory colonies.The infection rate of bee pathogens and the quantity of symbiotic bacteria are significantly different among different geographical areas;there are negative correlations between the incidence of some pathogens and the quantity of some symbiotic bacteria;Indicating that the migratory beekeeping,as well as seasonal,climate,nectar plant changes has negative impacts on worker longevity and colony health.