Study On Latent Infection Of Mouse With Babesia Microti And Its Influence On Co-infection With Other Protozoa

Babesia microti is the primary causative agent for the human and rodent babesiosis, an intraerythrocytic protozoa of the genus Babesia and belongs to the babesiidae, piroplasmida in phylum Apicomplexa. It is mainly transmitted to hosts through the biting of Ixodes scapularis tick, transfusion of blood or using the blood products, and causes severe clinical symptom and even death in human or animals.However, the latent infection always happened and became the infection resorce. The babesiosis is mainly popular in America, and the incidence of cases surged in recent years, meanwhile, it was found in some parts of in Europe and Asia, And in China,the infection of Babesia microti in human has also been reported. This emerging zoonotic infectious disease has brought a great threat to health of livestock and human.B.microti always causes a latent infection in hosts. Up to date, the proliferation of B.microti in host, the host immune response, and its influence to the co-infection of other pathogens have not been widely studied. In the present study, the proliferation of B.microti, its distribution in tissues of host, as well as the immune response of host and the influence of B.microti infection on the co-infection of other parasite have been investigated throughan artificial B.microti infection model.At the different time points post infection, B.microti was monitored by fluorescence quantitative PCR, and the results showed that B.microti could persist in the host for a long time and maintain a high titer in the late stage of infection. At the same time, it was ubiquitously distributed in the major organs and tissues of the host.B.microti could shorten the blood coagulation time by influencing the endogenous blood coagulation system, which tends to cause some thrombotic diseases.The antibody kept a higher level throughout the whole process of B.microti infection. At the different stages of B.microti infection,the differentiation of T lymphocyte subsets and the production of cytokines were anylzed by flow cytometry,and the results indicated that CD4+T cells played a crucial role in the protection of host from B.microti infection. The cellular immunity mediated by Th1 immune cells played a major role in the early stage of infection, while the humoral immunity played a major role in the later stage of infection.A comparative study on the parasite proliferation trend, blood physiological indices and the production of serum cytokine between normal mouse and spleen-deficient mouseinfected with B.microti have been investigated. As a result,B.microti caused more severe infection, more serious damage to the immune system and the coagulation system of host. The co-infection of Babesia microti with Toxoplasma goondii or Trypanosoma evansi respectively has been studied through building an artificial infection model. the results indicated that B.microti infection significantly aggravated T.gondii co-infection, while it had no obvious effect on T.evansi co-infection.The present study provied new thought for the study on its infeciton,spread and pathogenic mechanism, and thus a basis for the prevention and control of thisemerging infectious disease.