| Coccidiosis is recognized as a major parasitic disease of poultry and caused by the apicomplexamprotozoan Eirneria. The annual economic losses of poultry industry in the world is estimated at aboutUS$ 3 billion because of higher morbidity (50～70%) and mortality (20～30%, sometime up to even 80%)of this disease. Currently, chemotherapy is extensively used and the disease has largely been controlledthrough the use of anti-coccidial drugs added directly into feed. However, coupled with another factorthat the question of drug residue in poultry products is increasingly concerned, rapid appearance ofresistant Eimeria strains and very, few new drugs developed have stimulated studies on alternativecontrol methods, one of which is prophylaxis with a live vaccine. Therefore, the present studies werecarried out to develop new live vaccines against coccidiosis, and the results were as the followings.(1) Six species (E. tenella, E,. necatrix, E. maxima, E. acervulina, E. brunette, E. mitis and E.praecox) were isolated successfully from chickens in Lanzhou, Gansu province, by single oocysttechnique with plastic paper. The complete gene of 18S rRNA of E. acervulina (Ea18S rDNA) wascloned and sequenced, and then the phylogenetic relationship of E. acervulina with other Eimeriaspecies was also discussed.(2) The pathogenicity of six Eimeria species obtained in this study was investigated, showing thatthey were virulent. When infected with 6×10~4 oocysts each chicken, chicken's growth was inhibitedsignificantly, and half of chickens died when infected with 9×10~5 or 1.2×10~6 oocysts each chicken.Moreover, the whole fatality dose was 1.8×10~6 oocysts each chicken.(3) Three different live vaccines including LCV (tetragenous), LCV-1 and LCV-2 (hexavalen) weredeveloped, and their security and immuno-efficacy were investigated, according to the internationallyaccepted parameters, such as average relative ratio of weight up, OPG, intestinal lesion score, morbidityand mortality. The results showd that the chickens immunized with these vaccines performedsignificantly better than the control group, supporting that these vaccines are equal to previouslyreported ones in protection.(4) The efficacy of live vaccine LCV-2 was evaluated against coccidiosis in cage-reared andfloor-reared chickens demonstrating that the efficacy of LCV-2 was high in all birds under differentrearing conditions, and that its security was assured.(5) The effects of two differentβ-glucans derived from Lentinus edodes (Lentinan, L) andSaccharomyces cerevisiae (Zymosan, Z) were evaluated as an immunoenhancer. Body weight of thevaccine group (Ⅴ) was significantly higher than that of the challenge, L and Z groups at 7 dpi (day postinfection) and 14 dpi, respectively. However, Body weight of the L+V and the Z+V groups wassignificantly, higher than that of the V group at 7 dpi and 14 dpi, too. Moreover. the body weight of L+Vgroup was higher than that of the Z+V group at 14dpi. The similar trends in terms of oocyst output and immune organ index, especially thymus index and splenocyte proliferation were observed. As a result,both Lentinan and Zymosin used as immunopotentiator of coccidial vaccine enhanced immune response,and Lentinan was better than Zymosin.
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