日本血吸虫低感染度动物粪便排卵观察

Observation on fecal eggs from animals with low infection intensity of Schistosoma japonicum

目的观察低数量日本血吸虫尾蚴感染实验动物后在其体内存活和粪便排卵状况,为了解低水平流行态势下血吸虫低感染度动物传播能力奠定基础。方法取新鲜逸出的尾蚴2、4、6、8条,分别感染小鼠和家兔,饲养至感染后42d收集小鼠和家兔粪便,连续收集3d,利用浓集法镜检计数每克小鼠粪便虫卵数量(EPG),尼龙袋集卵孵化法观察家兔粪便毛蚴孵化率,以判定粪便中血吸虫卵排出情况。解剖全部实验小鼠与家兔,灌注法收集成虫,计算小鼠和家兔的感染率、体内合抱成虫检获率及虫负荷水平;同时观察小鼠和家兔肝脏表面虫卵结节,并收集家兔血清进行血吸虫抗体检测。结果小鼠感染尾蚴数量为2条时,其感染率、体内合抱成虫检获率、肝脏虫卵结节率和粪便排卵率分别为66.67%、58.33%、58.33%和58.33%,随感染尾蚴数量的增加四者趋于100%,但差异均无统计学意义(χ^(2)值分别为2.455,3.135,3.135和3.135,均P>0.05);小鼠体内平均虫荷和粪便平均EPG随感染尾蚴数量增加而增加(r值分别为0.588和0.533,均P<0.01)。家兔尾蚴感染数量为2条时,其感染率、体内合抱成虫检获率、肝脏虫卵结节率、血检阳性率和粪便孵化阳性率均为40%,除粪便孵化阳性率外(χ^(2)=0.003,P>0.05),其他指标均随感染尾蚴数量的增加趋于100%,差异均有统计学意义(χ^(2)值分别为4.473,4.473,4.473和6.758,P<0.05或P<0.01);随着感染尾蚴数量的增加,家兔体内虫荷增加(r=0.421,P<0.01)。结论感染一对日本血吸虫的小鼠和家兔即可检测到粪便排卵,提示小型适宜哺乳动物宿主传病能力强,应加强监测与控制,消除潜在的传染源隐患。

Objective To observe the survival of Schistosoma japonicum and fecal eggs excreted from experimental animals infected with low quantity of cercariae,so as to lay a foundation for understanding the transmission ability of animals with low infection intensity.Methods The mice and rabbits were infected with 2,4,6and 8fresh cercariae,respectively.After 42days of infection,the feces of mice and rabbits were collected for 3consecutive days.The number of eggs per gram of mice feces(EPG)was counted by microscopy,and the hatching rate of miracidia in rabbit feces was observed to determine the excretion of schistosome eggs in feces.Finally,all the mice and rabbits were dissected under euthanasia and the adult worms were collected.The infection rate,the rate of animals parasitized with paring worms and the worm burden were calculated.Meanwhile,the egg nodules on the liver surface of mice and rabbits were observed,and the serum of rabbits was collected for detection of antibodies against schistosome.Results When the quantity of cercariae for infecting mice was as low as 2,the infection rate,the rate of mice parasitized with paring worms,the rate of liver egg nodules and fecal eggs excretion were 66.67%,58.33%,58.33%and 58.33%respectively.With the increase of quantity of cercariae for infecting mice,the four indexes tended to be 100%,but there were no statistical significance(χ^(2)=2.455,P=0.117;χ^(2)=3.135,P=0.077;χ^(2)=3.135,P=0.077;χ^(2)=3.135,P=0.077).The average worm burden and EPG of mice increased with the quantity of cercariae(r=0.588,P=0;r=0.533,P=0.007).When the quantity of cercariae for infecting rabbits was 2,the infection rate,the rate of rabbits parasitized with paring worms,the rate of liver egg nodules,the positive rate of blood test and hatching rate of miracidia in rabbit feces were all 40%.Except the positive hatching rate(χ^(2)=0.003,P=0.956),other indexes tended to be 100%with the increase of the quantity of cercariae,and had statistical significance(χ^(2)=4.473,P=0.034;χ^(2)=4.473,P=0.034;χ^(2)=4.473,P=0.034;χ^(2)=6.758,P=0.009).With the increase of quantity of cercariae,the worm burden in rabbits increased(r=0.421,P=0.007).Conclusion Mice and rabbits infected with a couple of cercariae of Schistosoma japonicumcan lead to excretion of fecal eggs,suggesting that small suitable mammalian hosts have strong transmission ability.Therefore,surveillance and control measures should be strengthened to eliminate potential sources of infection.