福寿螺休眠期体内广州管圆线虫生长发育及其感染性的观察研究

Studies on the Growth-Development and Infectivity of Angiostrongylus cantonensis in Dormant Pomacea canaliculata

目的了解福寿螺处于休眠期对其体内感染的广州管圆线虫幼虫生长发育及其感染性的影响。方法来自实验室的广州管圆线虫L1幼虫感染福寿螺,感染后第1天螺置于25.0～25.5℃恒温室中休眠,观察体内幼虫生长发育情况,第13天起解剖观察幼虫生长发育情况。感染后第20天福寿螺置冬季室内自然变温条件下休眠2个月,每隔10d观察螺体内幼虫活力。检获的L3幼虫经口或腹腔注射感染SD大鼠,观察其感染性。同时观察螺的生存与体重变化情况,并以水族缸饲养螺作平行对照。结果25.0～25.5℃恒温条件下螺休眠不影响体内幼虫发育,且其幼虫发育历期为(16.3±0.6)d,显著快于水族缸饲养螺(17.6±0.96)d(t=5.72,P<0.01)。冬季室内自然变温条件下的休眠螺,生存率高于水族缸饲养螺(P<0.05),体重下降率为(33.5±4.3)%,也高于水族缸饲养螺[(9.0±2.3)%,t=10.68,P<0.01]。但随着休眠期的延长其死亡率增高(!2=18.31,P<0.01)。从存活螺体内检获的不同活力的L3幼虫均可感染SD大鼠。结论25.0～25.5℃恒温条件下螺休眠不影响体内幼虫发育,冬季室内自然变温条件下螺休眠或水族缸饲养,其体内幼虫均具有感染性。感染的福寿螺越冬方式,休眠明显优于水族缸饲养。

Objective To study the impact of dormancy of Pomacea canaliculata on the growth-development and infectivity of Angiostrongylus cantonensis. Methods The intermediate host snails （P. canaliculata） were infected with the first stage larvae of A. cantonensis from the laboratory. One day after infection the snails were kept dormant under 25.0-25.5℃ , and a sample of the snails was selected and dissected to examine the larval growth-development at various interval. Twenty days after infection, they were placed in room with natural winter conditions. Every 10 days a sample of the snails was dissected for larval activity. The third-stage larval infectivity from each group was identified by infecting SD rats. Meanwhile the survival and weight change of snails in the two groups were recorded, and were compared with those snails cultured in water under the corresponding temperature conditions mentioned above. Results The time for first-stage larvae of A. cantonensis in dormant snails to develop to third stage was shorter than that in the snails in aquarium. All the third stage larvae at various degree of activity recovered from snails in winter room conditions, including dormant snails and active snails in water, infected rats successfully. The dormant snails in winter room conditions stopped growing with decreased weight, but the survival rate was significantly lower than that of the snails in aquarium with the same condition along with an extending time of dormancy. Conclusion The development of A. cantonensis larvae has not been affected when snails are kept dormant under 25.0-25.5 ℃. The third stage larvae from snails at natural winter room temperature or in aquarium were all infective. As of the overwintering ways, it is better to keep the infected snails dormant than in the aquarium.