Precocious Strain Selection And Characteristics Study Of Eimeria Tenella In Yangling District Of Shaanxi Province

Avian coccidiosis is a parasitic protozoan belonging to the Phylum Apicomplexa. The pathogens invade the gut epithelium and result in coccidiosis in poultry throughout the world. This debilitating disease is characterized by poor weight gain and inefficient feed conversion. The annual worldwide cost is estimated to be about $2 billion. Eimeria tenella is the most pathogenic species of Eimeria. Currently, the disease is controlled by anticoccidial feed additives and it has played a major role in the growth of poultry industry, but some degree of resistance to all anticoccidial drugs has development and the reports of drug-residue in food have heightened the consumer's concerns. Live vaccine, consisting of either virulent coccidial strains or live attenuated parasites of several species, is proved to be effective in preventing coccidial infection. We have selected the precocious strain and studied the characteristics of E. tenella in Yangling District of Shaanxi province. Extraction the genomic DNA from E. tenella provided the basic material for further research in molecular biological study. This paper contains mainly two parts. ①Selecting the precocious strain and studying the bio-characteristics. A precocious strain of E. tenella was selected by repeated passages of oocysts that were early collected from faeces of previously infected chickens. We have studied on the pathogenicity,prepatent period,immunogenicity　and so on compared with the parental strain. The precocious strain had the following characteristics:the prepatent period of oocysts was 24 hours earlier than that of parental strain;The precocious strain was smaller in size, but it was similar to the parental in morphology;The pathogenicity and the reproductive capacity of precocious strain were all decreased in comparison with the parental strain. The immunogenicity was better than that of parental strain. After two times immunity the immunological protection of both strains was both high, and the ratio of occyst productive inhibition was all above 91%.　②Extracting the genomic DNA from E. tenella sporulated oocyst. In order to looking for a suitable method for extracting high quality genomic DNA from E. tenella sporulated oocysts, the Benzyl Chloride method was used in comparison with the usual method. Benzyl Chloride can efficiently break sporulated oocyst wall at 65℃. The results indicated that, the two methods were all good for extracting genomic DNA. The quantity and quality of the DNA extracted by two methods was all high. But the Benzyl Chloride method was not only simple and fast, but also not expensive. Therefore, the Benzyl Chloride method is a suitable method for large-scale preparation of genomic DNA from E. tenella sporulated oocysts .