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Korean J Parasitol > Volume 33(4):1995 > Article

Original Article
Korean J Parasitol. 1995 Dec;33(4):297-303. English.
Published online Dec 20, 1995.  http://dx.doi.org/10.3347/kjp.1995.33.4.297
Copyright © 1995 by The Korean Society for Parasitology
Effects of gamma-irradiation on the survival and development of Metagonimus yokogawai metacercariae in rats
Jong-Yil Chai,*1Sang-Joon Kim,2Jina Kook,1 and Soon-Hyung Lee1
1Department of Parasitology and Institute of Endemic Diseases, Seoul National University College of Medicine, Seoul 110-799, Korea.
2Department of Radiology, Dankook University College of Medicine, Chonan 330-714, Korea.
Received September 14, 1995; Accepted November 15, 1995.


To evaluate the feasibility of irradiation as a control measure for metagonimiasis, the metacercariae of Metagonimus yokogawai were irradiated with gamma ray, either after isolation from the sweetfish (Plecoglossus altivelis) or in situ of the fish, and their survival and development in rats were observed at 7 days post-infection. The radiation dose varied from 5 to 100 Gy for the metacercaria-irradiation group and from 5 to 500 Gy for fish-irradiation group. The results showed that the worm recovery rate from the irradiation groups decreased as the radiation dose was increased. Higher doses of radiation were required for the fish-irradiation group to obtain the same results as the metacercaria-irradiation group. The LD50 of the metacercaria-irradiation group was 4.5 Gy, whereas that of the fish- irradiation group 6.2 Gy. A few number of worms which survived until 7 days in rats were severely retarded especially in the growth of their reproductive organs, i.e., complete or partial failure in the development of testes and formation of uterine eggs. The present study revealed that irradiation of sweetfish by 200 Gy is effective to control infectivity as well as development of M. yokogawai metacercaria in rats.


Figs. 1-4
Fig. 1. A 7-day old adult worm of M. yokogawai recovered from a rat of non-irradiated control group showing its normal body contour, many intrauterine eggs, well-developed ovary, seminal vesicle, seminal receptacle, vitelline follicles, and two testes. Acetocarmine stained. Fig. 2. An age-matched specimen recovered from a rat infected with 100 Gy-irradiated metacercariae (metacercaria-irradiation group) showing no uterine eggs, no vitelline follicles, pooly developed ovary, and only one testis. Acetocarmine stained. Fig. 3. Another age-matched specimen recovered from a rat infected with 200 Gy-irradiated metacercariae (fish-irradiation group) which shows no uterine eggs, no ovary, no vitelline follicles, and two poorly developed testes. The excretory bladder slightly expanded. Acetocarmine stained. Fig. 4. Another specimen recovered from 200 Gy fish-irradiation group showing no eggs and no reproductive organs. The bladder is distended severely. Acetocarmine stained.

*Bar represents 100 micrometers.


Table 1
Recovery rate of M. yokogawai from the rats of metacercaria-irradiation group

Table 2
Recovery rate of M. yokogawai from the rats of fish-irradiation group

Table 3
Morphological features of M. yokogawai recovered from the rats infected with normal (non-irradiated control group) or irradiated metacercariae (metacercaria-irradiation group or fish-irradiation group)

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