KILLING EFFECT OF GAMMA-IRRADIATION ON ANGIOSTRONGYLUS-CANTONENSIS INSNAILS

Cobalt-60 gamma irradiation was used to kill the larvae of Angiostrong ylus cantonensis in four groups of snails that were irradiated at a ra te of 15.4 Gy/min for 16.23 min (0.25 kGy), 32.47 min (0.50 kGy), 48.7 0 min (0.75 kGy), and 64.94 min (1.00 kGy), respectively. Third-stage (infected stage) larvae were isolated from these snails and 50 were ad ministered to each experimental animal via an esophageal tube. At a do sage of 0.25 kGy, the mean +/- SD number of worms recovered from 30 ra ts and 30 mice was 15.6 +/- 6.5 and 11.3 +/- 6.2, respectively. These were significantly different from the number of worms recovered from t he nonirradiated (control) groups, which were 28.9 +/- 9.6 (P < 0.05) and 16.6 +/- 10.3 (P < 0.05) for rats and mice respectively. Worms and cellular infiltrations in lung tissue of rats were histopathologicall y identified in the 0.25-kGy-irradiated group as well as in the contro l group. Worms and eosinophilic meningitis were also noted in the brai n tissue of mice in control groups. No worms or pathologic findings we re observed in the heart, lung, or brain tissue of rats or mice infect ed with larvae irradiated at or exceeding 0.50 kGy. It is therefore co ncluded that a dosage of 0.50 kGy is sufficient to prevent successful infection in mice and rats.