Abstract: 　Objective] To find out the cause and transmission factors of an outbreak of eosinophilic meningoradiculitis in Wenzhou City during October to November in 1997. [Methods] In addition to a retrospective cohort study on 182 persons who had dined at a same restaurant of the city, etiological and immunoserological investigations were conducted. [Results] Among 105 cases who had eaten the undercooked Ampullaria gigas in that restaurant,47 cases were infected,the incidence rate was 44.8%;whereas none of the persons who did not eat the under cooked Ampullaria gigas in that restaurant got the infection, the difference between the two groups being significant( P <0.001).The incidence rate of the cases who had eaten 4 and more pieces of the undercooked Ampullaria gigas was 86.2%(25/29),while that of those who had eaten less than 4 pieces was 28.9%(22/76), the difference between the two being very significant(χ 2=27.83, P <0.001,RR=2.98).The third stage larvae of the Angiostrongylus cantonensis were found out from Ampullaria gigas living in the same locality,and the adult worms of Angiostrongylus contonensis were found out from the rats living in the locality else.The positive rate of serum anti Angiostrongylus cantonensis antibody in the patients was 84.0%. [Conclusion] On the basis of the clinical,epidemiological,immunoserological and etiological investigations, an outbreak of the angiostrongyliasis cantonensis caused by eating undercooked Ampullaria gigas was confirmed.

Key words: Angiostrongyliasis cantonensis, fulminating epidemic, Ampullairia gigas, eosinophilic meningoradiculitis, epidemiological study.