多种实验动物对藐小棘隙吸虫易感性的实验研究

SUSCEPTIBILITY OF VARIOUS ANIMALS TO EXPERIMENTAL INFECTION WITH ECHINOCHASMUS LILIPUTANUS

为观察不同实验动物对藐小棘隙吸虫的易感性 ,以定量囊蚴感染幼犬 2只、幼猫 2只、新西兰兔 3只、昆明小鼠 10只、猪 2头、鸡鸭各 10只 ,并观察犬体内藐小棘隙吸虫成虫寿命、日产虫卵量以及排卵动态。结果所有感染犬、兔、猫均检获成虫 ,10只小鼠有 7只感染成功 ,其他实验动物均为阴性 ;犬、兔、猫和鼠的获虫率分别为 5 6 .15 %、5 1.45 %、2 9.82 %和 11.93%。实验犬和兔的获虫率、所获虫体大小以及虫体子宫含卵数均明显高于或大于实验猫和小鼠。上述结果表明 ,犬和兔是藐小棘隙吸虫适宜终宿主 (其中兔为终宿主新记录 ) ,猫次之 ,小鼠的易感性较低。实验犬感染藐小棘隙吸虫后第 13d开始从粪便中排卵 ,此后排卵量迅速增加 ,感染后 3个月达到高峰 ,感染后 6个月时明显下降 ,10个月时排卵量处于很低水平 ,此后 10个月仍维持同一水平 ,未见明显升降或停止排卵现象。犬体内 13～ 2 5日龄藐小棘隙吸虫成虫日产卵量为 ( 48± 2 7)个。成虫在犬体内的寿命超过 2 0个月。另外 ,3只兔感染日本血吸虫 ( 2 0 0 0尾蚴 /只 ) 2 8d后再用藐小棘隙吸虫囊蚴攻击感染 ,结果对藐小棘隙吸虫产生了明显的抗性 ,与无血吸虫感染的实验兔相比其减虫率达到 86 .78%～ 10 0 % (平均为 92 .0 9% )。藐小棘隙吸虫

A study on susceptibility of various animals to Echinochasmus liliputanus was carried out. 2 dogs, 3 rabbits, 2 cats, 10 mice, 2 pigs, 10 chicks and 10 ducks were experimentally infected with metacercariae. All dogs, rabbits and cats, and 7/10 mice were successfully infected with worm recoveries 56.15%, 51.45%, 29.82% and 11.93% respectively. None of pigs, chicks or ducks was infected. The worm recovery and number of eggs per worm from dogs and rabbits were significantly higher and the worm sizes significantly larger than those from cats and mice. It is strongly suggested that dogs and rabbits are more susceptible as permissive definitive hosts than are cats and mice for E. liliputanus. The fecal egg output of dogs was observed. The eggs firstly appeared in dogs feces the 13th day postinfection (p.i.). The daily egg output of 13 to 25 days old worms of E. liliputanus was 48±27 per worm. Then the egg output increased rapidly and reached to the peak 3 months after infection. Six months p.i., the egg output decreased significantly and reached to a very low level 10 months p.i. This low level remained similar during a further 10 months. These results suggested that E. liliputanus in dogs intestines was able to survive for at least 20 months. In another experiment, 3 rabbits with a primary 24dayold Schistosoma japonicum infection were challenged with E. liliputanus metacercariae. The results showed that S. japonicum infection induced 86.78%-100% resistance to a heterologous challenge with E. liliputanus. The E. liliputanusrabbit model appeared to be of value in studies on the mechanism of heterologous resistance and hostparasite relationships.