鹅球虫Eimeria nocens的生活史及致病性研究

Studies on Life Cycle and Pathogenicity of Eimeria nocens in Domestic Goslings

16只10日龄小鹅分别接种1．0×10^5～1．0×10^6个Eimeria nocens孢子化卵囊，在接种后30～336h期间内分期剖杀，对E.nocens的生活史和致病性进行了动态性观察。在内生性发育过程中，E.nocens至少有3个世代的裂殖生殖阶段。有两种类型的裂殖体存在，一种在接种后54～78h发育成熟，为第1代裂殖体，每个含10个左右的裂殖子；另一种在接种后102～240h发育成熟，为第2代或第3代裂殖体，每个含25个左右的裂殖子。接种后198h左右虫体开始进入配子生殖阶段。从接种后第10天开始有卵囊排出，显露期为4d。25℃下卵囊孢子化时间为60～72h。E.nocens寄生于空肠后部、回肠、盲肠、直肠和泄殖腔的绒毛和肠腺上皮细胞及固有膜中。在裂殖生殖后期、配子生殖和卵囊排出期间组织病变比较明显，主要包括肠粘膜上皮坏死和脱落、肠壁水肿、出血和炎性细胞浸润以及肠绒毛萎缩等，尤以回肠及其邻近部位最为严重。感染鹅腹泻、食欲下降、消瘦乃至死亡。

Sixteen 10-day-old artificially-reared coccidia-free goslings were inoculated orally with 1.0×105-1.0×106 sporulated oocysts of Eimeria nocens,respectively, and killed at intervals from 30 h to 336 h after inoculations. The life cycle and pathogenicity of E. nocens were observed chronologically. The results showed that at least 3 generations of meronts developed in the endogenous stage of the life cycle of E. nocens. Two types of meronts were found. The first completed maturation at 54 to 78 h after inoculation. These meronts were the first generation meronts, each forming about 10 merozoites. The second completed maturation at 102 to 240 h after inoculation. These meronts were the second or third generation meronts, each forming about 25 merozoites. Development of gametes began at about 198 h after infection. The prepatent period was 9 d and discharge of oocysts continued for 4 d. Sporulation of oocysts occurred in 60-72 h at 25℃. E. nocens invaded posterior jejunum, ileum, ceca, rectum and cloaca. Developmental stages were localized within the epithelial cells of villi and crypts and in lamina propria. Marked histopathological changes including desquamation and necrosis of intestinal epithelium, submucosal edema, hemorrhages, infiltration of inflammatory cells and villous atrophy presented during the periods of late merogony, gamogony and oocyst shedding, but most pronounced in the ileum and the regions adjacent to it. The infected goslings showed severe diarrhoea with necrotic epithelium and blood in the feces, anorexia, emaciation and even deaths, suggesting that E. nocens is highly pathogenic for goslings.