[Studies on the growth-development and infectivity of Angiostrongylus cantonensis in dormant Pomacea canaliculata].

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 degrees C, 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 degrees C. 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.