| Toxoplasma gondii is a protozoon infecting both human beings and animals all over the world.1/5 global population have infected toxoplasmosis. It is a lethal threat for immunodepressed and organ transplant patients, while it could result in abortion, teras and stillbirth to the gravidas. Pigs could also infect Toxoplasma gondii and show abortion or collective symptoms. The pork containing Toxoplasma gondii cysts is the maior risk for human infection. There is no effective vaccine to prevent the infection. Thus the prevention and control of Toxoplasma gondii is most dependent on the drugs. However, drug resistance strains of Toxoplasma gondii were engendered due to the nonstandard use for a long time. Drug resistance increases the difficulty in preventing and controlling this parasites in the large scale pig farms. Owing to the complex life cycle of Toxoplasma gondii, ELISA coated by single Toxoplasma gondii antigen could just acquire low sensibility in different infection stages.In the present study, multiepitope antigenic gene (MAG), splicing antigenic epitopes of SAG1,GRA1,ROP2. GRA4 and MIC3 selected as the advantage antigens, showed good antigenicity by DNAstar. Recombinant plasmid pGEX-KG-MAG was constructed and expressed stably in E.coli BL21-CodonPlus. MAG showed the immunogenicity by Western-blot following optimizing the expression condition. MAG-ELISA using MAG as the detection antigen was developed and used to detect positive serum for five common pig diseases, the result showed negative; coefficient of variation less than 10% during the repeatability test in different batch. The material of ELISA can be stored at least 6 months at 4℃; 797 clinical pig serum were detected using MAG-ELISA, the results showed the 3.0% higher detection rate than AG-ELISA, that means the method we used is sensibility and specificity, and also has long shelf life.Toxoplasma gondii positive samples were collected from different areas and then amplified DHPS, DHFR and Cytb gene and performed sequencing in order to verify the existence of drug resistance Toxoplasma gondii strains. But there was no resistance mutation among 20 samples. Drug resistance strains of Toxoplasma gondii were not generally prevalence in domestic.Epidemiological surveys were carried out in 15 large scal pig farms in Hubei and Henan provices from June 2008 to August 2009. The positive rate was 24.5%. The farms were divied into three groups based on the positive rate of Toxoplasma gondii:high prevalence(positive rate>30%), moderate prevalence(15%< positive rate<30%), slightly prevalence(positive rate<15%). Prevention and control measures were conducted corresponding the different groups. The positive rates of the three groups decreased from 33.1%,23.3%and 12.6%to 23.8%,13.0%and 9.7%, respectively, after one year the measures conducted. The preventive and control effect was significant. Meanwhile, the antibody test was carried out to detect the developing tendency of Swine fever. The positive rate of anti-Toxoplasma gondii antibody decreased from 36.9%to 23.1%, while the positive rate of anti-Swine fever antibody increased from 65.9%to 77.6%. These results demonstrated that the prevention and control measures on Toxoplasma gondii in pig farms could promot the immune effect on the other diseases.By MAG-ELISA we constructed in this study, the problem on low sensibility of anti-Toxoplasma gondii antibody detection through single antigen were solved. There was no drug resistance strains of Toxoplasma gondii prevalence in domestic. The feasibility of of prevention and control measures on Toxoplasma gondii was proved according good effect on the study in large scal pig farms. |
PDF Full Text Request