The Changes Of Micro-ecological Of Diseased Yangtze Finless And Research On Its Protection Under Ex-situ

The Yangtze finless porpoise are the freshwater species that live in Yangtze River,Poyang Lake,Dongting Lake and other large lakes along the river.In recent years,due to the rapid industrial and agricultural development,Yangtze River ecosystem is deteriorating continuously which is resulting in a rapid decline of Yangtze finless porpoise's population.According to the reports,population has dropped from 2700 to2014 during the period of 1990s-2017.So,a better strategy e.g.Ex-situ conservation is needed on immediate basis for these species.Ex-situ conservation is one of the important measure which plays an important role in the conservation and scientific research of finless porpoise.However,diseases and poor feeding management in ex-situ conservation area may seriously affect the growth and breeding of Yangtze finless porpoise's population.In recent years,the Yangtze finless porpoise has been suffering from frequent diseases and improper feeding management which may imminent to high mortality and low reproductive efficiency.Therefore,it is necessary to carry out systematic research on the infectious diseases(bacterial or viral)and the feeding management of the Yangtze finless porpoise in the ex-situ conservation area.For this purpose preliminarily understanding of pathogen's epidemiology,their biological characteristics,and establishment of techniques for feeding management in ex-situ conservation areas are important.In this study,we carried out the pathogenic investigation of bacterial and viral diseases of the Yangtze finless porpoise;based on the high-throughput sequencing technology.We also studied the molecular biology of six harmful bacteria of the Yangtze finless porpoise,and some feeding management in the ex-situ reserve.The results are as follows:1.Epidemiological investigation of bacterial diseases in the Yangtze finless porpoiseThrough isolation,staining,chemical,and PCR identification,462 tissue samples of the Yangtze finless porpoise were identified.Samples were taken from respiratory pores,feces,blood,visceral tissue,skin lesions,ascites,pleural effusion,etc.The bacterial macro genomic method were also used to study the intestinal microflora of healthy andsick Yangtze finless porpoise.From the total samples,655 bacteria were isolated and identified e.g.Aeromonas sobria,Staphylococcus epidermidis,Bacillus megaterium,Micrococcus,Bacillus Firemus,Bacillus pumilus,Proteus,Klebsiella pneumoniae,Stenotrophlomonas maltophilia,Escherichia coli,Clostridium Perfringens,Lactobacillus,Streptococcus,Pseudomonas aeruginosa,Staphylococcus aureus,Aeromonas hydrophila,Nocardia,Vibrio,Acinetobacter,Morganella Morganii,Enterococcus,Helicobacter pylori,Campylobacter,Flavobacterium,Bacillus cereus,Enterococcus faecalis,Plesiomonas shigeloides,Aeromonas Veronii,Aeromonas salmonicida,Edwardsiella Ictaluri and Erysipelothrix.Among them,11 kinds of bacteria,such as Clostridium perfringens,Vibrio and Edwardia,were first found in the Yangtze finless porpoise.In the study of bacterial macro genome,340 species of bacteria were detected,15 of which were common pathogenic bacteria e.g.Escherichia,Lactobacillus,Streptococcus,Pseudomonas,Pseudomonas,Flavobacterium,Aeromonas,Nocardia,Vibrio,Pasteurella,Morganella,Staphylococcus,Enterococcus,Helicobacter pylori and Campylobacter.2.Research on the biological characteristics of the main pathogens of the Yangtze finless porpoiseThe biological characteristics of six major pathogens(Aeromonas hydrophila,Aeromonas veronii,Aeromonas salmonicida,Morganella morganii,Staphylococcus aureus and Escherichia coli)were studied by microbiology,molecular biology,veterinary pharmacology and veterinary pathology.The results of present study indicated that the isolated strains could grow well according to the conventional culture method with no significant difference with other animal origin bacteria.Biochemical studies and 16 s r RNA sequence analysis suggested that all kinds of bacteria had the same phenotype.Study of bacterial drug resistance showed six kinds of bacteria with a certain degree of drug resistance,of which E.coli was the most resistant,S.aureus was the weakest one,while the Aeromonas had some difference among bacteria.The experiment of BALB/c confirmed that six kinds of bacteria have pathogenicity to mice.A.veronii and A.salmonioides were the most pathogenic while S.aureus was the weakest one.A little difference in pathological changes was noticed in infected mice,in which pulmonarycongestion,hemorrhage and liver congestion,degeneration,and necrosis were the main pathological changes.3.Study on the viral diseases of the Yangtze finless porpoiseThrough the viral metagenomics,the virus community of(heart liver,spleen,kidney,skin etc.)collected samples from Yangtze finless porpoise(who died during 2017-2019)were studied.From the analysis of samples 10600 contigs were obtained in which 65 viruses were detected.Among them,25 viruses were identified based on reference sequences and 42 viruses were identified based on Denovo sequences.At the family level,the dominant viruses were Myoviridae,Herpesviridae,Retroviridae,Sipoviridae,Nimaviridae,Ackermanniviridae,Poxviridae,Inoviridae,Podoviridae,Arenaviridae and Caudovirales unclassified.In addition Herpesvirus,Phage virus,Retrovirus,Filovirus,Poxvirus and Arenavirus were first first time found in Yangtze finless porpoise.4.Feeding management and disease control of Yangtze finless porpoise in ex-situ conservation area.Based on clinical practices and data analysis about the feeding and disease control management in the ex-situ conservation(enclosed net environment;convalescent pool)were studied.Technical specifications for feeding management in different growing environments were formulated.Through the study of nearly 100 blood samples,physiological and biochemical indicators,the normal threshold and reference range of blood routine and biochemistry of healthy Yangtze finless porpoise were statistically summarized.The diagnosis of the disease was carried out through the correlation between physiological and biochemical indexes.In conclusion,this study clarified the epidemic characteristics of bacterial and viral pathogens(in which six are common)of the Yangtze finless porpoise.It reveals their biological characteristics and provide reference information for the development of different drugs and vaccines.It also helps in the establishing of feeding management in the ex-situ conservation area of the Yangtze finless porpoise.As,feeding management and disease control are two important aspects in such controlled environment.So,continuesimprovement in the feeding and disease control management are main key points in each growth stage.Such protocols can effectively solve the current situation of Yangtze River finless porpoise in ex-situ conservation and may provide a strong theoretical support for the protection of cetaceans(Yangtze finless porpoise;Sousa chinensis).