Study On The Relationship Between The Gut Microbes Of Hippocampus Erectus And Their Diseases

The lined seahorse,Hippocampus erectus,native to the Atlantic Ocean,mainly inhabits shallow seas and coral reefs,which is a kind of highly valued species in both medicinal and aquarium.The aquaculture of the seahorses,Hippocampus is growing rapidly in China because of the increasing demand.The demand for the seahorses is mainly reflected in the high value of Chinese traditional medicine,according to the Chinese medicine theory.In the last decade,the population of wild seahorses has dropped sharply due to the overexploitation of the wild and the destruction of the habitat.All seahorse species have been listed on the Appendix II of CITES and IUCN Red List since 2004.Aquaculture of seahorses has been considered as an ideal way to solve the imbalance between market demand and wildlife conservation.Therefore,the development of the Hippocampus spp.aquaculture is essential.However,the threat of various diseases has seriously affected the healthy development of the aquaculture industry.In the breeding process of the H.erectus in northern China,disease has frequently occurred,the morbidity is rapid and the death is serious.The threat of various diseases has seriously affected the healthy development of the aquaculture industry.Although most fish diseases can be treated with antibiotics,the overuse of antibiotics may produce many potential threats,which are not conducive to the sustainable and healthy development of the aquaculture industry.Therefore,it is essential to further study the pathogens of various fish diseases and then we can develop biological control on this basis.Specific vaccines can be developed from isolated pathogenic bacteria,which provide effective way for disease treatment.Aiming at the disease of H.erectus,this paper mainly focuses on the following points:?1?In this study,dominant strains were isolated from the lesion tissue and intestine of the H.erectus with epidermis ulcer syndrome.The artificial infection results suggested that strain HDM-2 was the pathogen causing epidermis ulcer syndrome,and the LD₅₀0 of strain HDM-2 was about 2.89�10⁸ CFU/mL.Strain HDM-2 was identified as Vibrio harveyi with physiological and biochemical identification and molecular biological identification methods.Strain HDM-2 was about 2.2�4.75?m,with peritrichous flagella and capsule under transmission electron microscope.Antibiotic sensitivity test showed that strain HDM-2 was highly sensitive to florfenicol.The histopathological observation results suggested that skin,liver and gills were severely damaged by HDM-2.To study the pathogenic mechanism of strain HDM-2,specific primers were used to detect the presence of virulence genes.Result showed that strain HDM-2 was positive for toxR,LuxR,VhhA,RecA,VhhB and vah1.?2?In this study,dominant strain CY2-1 was isolated from the intestine of the H.erectus with enteritis.Artificial infection results suggested that strain CY2-1 was responsible for enteritis of H.erectus.Strain CY2-1 was identified as V.parahaemolyticus with physiological and biochemical identification and molecular biological identification methods.Antibiotic sensitivity test showed that strain CY2-1 was highly sensitive to florfenicol.Massive infiltration of inflammatory cells and more goblet cells were observed in the H.erectus infected by CY2-1 in the histopathological observation.In order to explore the relationship between the enteritis and intestinal microorganisms as well as the overall changes of microorganisms in living water environment,the composition and changes of intestinal microorganisms in healthy and diseased H.erectus were determined by high-throughput sequencing technology.The results showed that the enteritis was closely related with intestinal microorganisms and the overall changes of microorganisms in living water environment.?3?In this study,the liver and kidney of H.erectus with epidermal ulcer syndrome were selected at 0,24,48 and 72 hours after infection,and the contents of SOD,C3,LZM and ACP were measured by commercial kits.We studied the composition and proportion of lymphocyte in the healthy and infected H.erectus,results showed that compared with the control group,the number of granulocytes in the H.erectus decreased significantly and the number of lymphocyte increased significantly.In addition,the phagocytic activity of macrophages in healthy and diseased H.erectus was measured.Results showed that the phagocytic activity of macrophages in healthy and diseased H.erectus was 44.09%and52.8%respectively,indicating that the phagocytic activity of macrophages in diseased H.erectus was increased.These results preliminarily revealed the host's immune response mechanisms against the pathogen invasion.In this study,inactivated vaccines were prepared on the basis of the two pathogens isolated from the H.erectus.The results of application showed that the relative percent survival?RPS?of the two pathogens were 42%and 28%respectively.