不同发育期福寿螺对广州管圆线虫易感性的实验研究

Studies on Susceptibility of Pomacea canaliculata of Different Developmental Stages to Infection with Angiostrongylus cantonensis

目的探讨和了解广州管圆线虫幼虫对不同发育期福寿螺感染的差异。方法将实验室饲养的子1代福寿螺按体重分为4个等级,分别为螺苗级、仔苗级、中螺级和成螺级。应用福建同一来源并经实验室传代的广州管圆线虫I期幼虫分别感染4级螺,观察比较其感染率、感染死亡率、感染度、III期幼虫(感染期幼虫)大小和幼虫在螺体的发育速度及分布情况。结果4级螺均能被广州管圆线虫感染,其感染率在76%和100%之间,差异无显著性(P>0.05)。螺级越小感染死亡率越高。中螺级的感染度较高,体内超过100条幼虫的螺数也较多。螺级间螺体幼虫发育状态基本相似。各级螺中的III期幼虫大小及III期幼虫出现前期和盛期均无明显差异(P>0.05)。幼虫广泛分布于螺体各脏器与肌肉等处,但以肺与肌肉中居多。各级螺内III期幼虫均能成功感染大白鼠。结论不同发育期福寿螺对广州管圆线虫均易感而相容,螺级间螺体幼虫发育状态基本相似。螺苗级和仔苗级福寿螺在传播广州管圆线虫病中的潜在危害应予进一步认识。

Objective To study the susceptibility of Pomacea canaliculata of different developmental stages to Angiostrongylus cantonensis infection. Methods P. canaliculata snails breeding at laboratory were divided into four rank （ Ⅰ-Ⅳ） according to the weight, and infected with the first stage larvae of A. cantonensis from Fujian Province. Their mortality, infection rate, worm burden, and the size, development and distribution of larvae in snails were examined. Results Snails at different developmental stages were readily infected with A. cantonensis. The infection rate was between 76% and 100%, with no significant difference among the groups （P〉0.05）. Snails at earlier developmental stage showed higher mortality. The heaviest worm burden and the largest number of snails harboring more than 100 larvae were found in snails of rank Ⅲ. In general the larvae in snails showed a synchronous development in the groups. Sizes of the third stage larvae in snails of various ranks were homogeneous. The period before the third stage larva emergence and the time for a peak percentage of the larvae exhibited no significant difference among the four ranks. The larvae widely distributed in various parts of snails, with more in the lung and foot, and larvae from snails of different ranks could all infect rats successfully. Conclusion P. canaliculata of the four ranks can all be infected by the first stage larvae of A. cantonensis. Rank Ⅲ snails may be better for studying the relationship between P. candiculata and A. cantonensis. The potential role of young snails in angiostrongyliasis transmission should be recognized.