Shrimp And Crab Spiroplasma Disease Immunohistochemistry And Pathology Comparative Study

Spiroplasma eriocheiris is a new pathogenic microorganism in aquatic crustaceans in recent years. The pathogen can cause tremor disease of Chinese mitten crabs, also lead to large-scale mortality of Procambarus clarkii, Penaeus vannamei and Macrobrachium rosenbergii, which caused a great threat to economic aquatic crustaceans in china.Spiroplasma is smallest of prokaryotic cell organism, can pass through the membrane with 220nm pore size. It has a special tip structure which assists for its adherence to the surface of host cells, which is related to infection and pathogenesis. The infection of the pathogen in host body showed two forms:dispersed and collective (the number of spiroplasmas multiply and aggregate in host cell and form inclusions). Spiroplasmas are small, not to be able identified under the light microscope, and so it is difficult to define the pathological features of spiroplasma infection by normal hematoxylin-eosin (HE) staining.The presented paper carried out the pathological studies on different tissues of Chinese mitten crabs E. sinensis and crayfish Procambarus clarkia which infected by S. eriocheiris with immunohistochemistry. All the tissues, including heart, liver pancreas, intestine, gill, and muscle showed positive reaction. A large number of spiroplasmas were found in the connective tissue and aggregated to form inclusion bodies, showed brown granular, the single dispersed spiroplasma showed yellow.By preliminary experiment that Macrobrachium rosenbergii were infected with different strains of spiroplasma and twenty days of observation statistics, showed the individual death of M. rosenbergii a few days after inoculation, either the experimental group or control group, the reason is most likely that inoculation caused mechanical damage and stress responses for individual death. The mortality of the infection with spiroplasma strain BY08-1(from E. sinensis) was higher than the control group, but was not very high (33.3%). Along with the time, the mortality rates of M. rosenbergii that infected with the strain MR10 which was isolated from M. rosenbergii increased significantly, and to 95%. There is significant difference in pathogenicity to M. rosenbergii with different strains isolated from differenct original hosts (E. sinensis or M. rosenbergii, although the two strains were both isolated from aquatic crustaceans. Polyclonal antibody of S. eriocheiris and MR10 reacted with tissues of M. rosenbergii which infected by spiroplasma in naturewith immunohistochemistry method, respectively, the result showed that the response intensity of polyclonal antibody of MR 10 was more than that of S. eriocheiris, which also confirmed that there was difference of infection of spiroplasmas with different strains isolated from different aquatic hosts.Based on the above results, there were infective differences among the different hosts with different spiroplasma stains isolated from different hosts. The ultra-pathological observations that infected with different strains of spiroplasmas were compared. The studies suggested that spiroplasmas parasited mainly in the cytoplasm with the form of inclusion bodies in the various tissues of crabs that suffered from S. eriocheiris, with dispersed form in various tissues of M. rosenbergii that suffered from MR10.There were different virulence and infectivity of aquatic spiroplasma strains which from different hosts, and the polyclonal antibodies were also different, that may caused by variation among different hosts and host selection pressures.