Study On Flea-associated Bacterial Communities In Inner Mongolia Autonomous Region By 16S RRNA Gene Sequencing Technology

BackgroundFleas belong to the Arthropoda,Insecta,and Siphonaptera.Fleas are small,wingless,and good at jumping,and are mainly parasitic on warm-blooded mammals and birds.Fleas are storage hosts and vector for a variety of pathogens,such as Yersinia pestis,Myxomavirus,Hymenolepis diminuta,Taenia canis,Rickettsia,Bartonella,etc.At the same time,fleas can transmit plague,hemorrhagic fever with renal syndrome,endemic typhus and other infectious diseases.The occurrence of flea-borne diseases will cause serious harm to human health.The number of fleas and the composition and distribution of flea are influenced by factors such as environment and host.Changes in any these factors will cause ecological imbalance and affect the occurrence and prevalence of flea-borne diseases.Plague epidemic occurred many times in Inner Mongolia Autonomous Region.Therefore,it is of great public health significance to analyze the bacterial community composition and diversity in fleas in the eastern Inner Mongolia,and to explore the factors affecting the bacterial community composition for the control of flea-borne diseases.Objectives1.To describe the bacterial community composition and diversity in flea,and characteristics of bacterial community between different flea in eastern grasslands of Inner Mongolia;2.To discuss the influencing factors of bacterial community composition of fleas in the eastern grasslands of Inner Mongolia;3.To study the infection and phylogenetic analysis of Bartonella infection by fleas of wild rodents in the eastern grasslands of Inner Mongolia.MethodsIn May,July,and September 2021,Rodents were collected at 6 sites in the Inner Mongolia Autonomous Region,wild.We used animal surface collection to collect fleas from the body surface of wild rodents.All of them were identified by morphological and molecular methods.The metagenomic 16S rRNA gene V4 profiling of bacteria were sequenced by Illumina Miseq PE250 sequencing platform to describe the bacterial community in flea,to evaluate bacterial diversity and to identify the predominant microorganisms and distribution of pathogens.We used beta diversity metrics to assess the effects of flea species,flea sex,host species,collection site and date,elevation,average monthly precipitation,and average monthly temperature on bacterial community structure.Results1.A total of 9 332 936 Tags and 4 766 OTUs were used to describe the characteristics of bacterial communities of 74 fleas from 3 flea species.The predominated phyla in the fleas wer e Proteobacteria,Bacteroidetes,Firmicutes,and Actinobacteria sequentially.Alphaproteobac teria class showed the highest relative abundance.At the genus level,the top four are Bartone lla,Wolbachia,Candidatus-Lariskella,and Candidatus-Cardinium.2.At the phylum level,Proteobacteria accounted for a higher proportion in Frontopsylla luculent and Citellophilus tesquorum,while Bacteroides and Firmicutes accounted for a higher proportion in Nosopsyllus laeviceps.At the genus level,Bartonella and Wolbachia accounted for a relatively high proportion in Frontopsylla luculent,Candidatus-Cardinium and spiroplasma accounted for a relatively high proportion in Nosopsyllus laeviceps,and Bartonella and Candidatus-Lariskella accounted for a relatively high proportion in Citellophilus tesquorum.3.The flea species,site,rodent host,collection date,and elevation had a significantly with community composition when all samples were analyzed simultaneously.Elevation,average monthly precipitation,and average monthly temperature significantly covaried with bacterial community composition across all samples.4.Bartonella carried by fleas were identified as B.clarridgeiae,B.heixiasiensis,B.grahamii,B.krasnovii,and B.washoensis,respectively.Frontopsylla luculent carried B clarridgeiae、B.heixiaziensis、B.grahamii,Nosopsyllus laeviceps carried B.Krasnovii,and Citellophilus tesquorum carried B.washoensis、B.clarridgeiae、B.krasnovii.Conclusions1.The predominated phyla in the flea in the eastern grasslands of Inner Mongolia were Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes sequentially.2.Flea species,site,sex,altitude,monthly mean precipitation and monthly mean temperature had a significantly with community composition.3.Bartonella carried by fleas were identified as B.clarridgeiae,B.heixiasiensis,B.grahamii,B.krasnovii,and B.washoensis.4.The species of Bartonella carried by different fleas were slightly different,and the same species of Bartonella can infect a variety of fleas.In conclusion,the parasitic fleas in the eastern Inner Mongolia naturally carried a wide variety of pathogenic bacteria.Flea itself and environmental factors had a certain influence on the carrying of flea pathogens.Therefore,the density of fleas and their own pathogen should be tested regularly,and the prevention and control of fleas should be strengthened to effectively control the occurrence and prevalence of flea-borne diseases.