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Korean J Parasitol > Volume 27(3):1989 > Article

Original Article
Korean J Parasitol. 1989 Sep;27(3):187-195. English.
Published online Mar 20, 1994.  http://dx.doi.org/10.3347/kjp.1989.27.3.187
Copyright © 1989 by The Korean Society for Parasitology
The effects of gamma irradiation on the survival and development of Clonorchis sinensis metacercariae
S H Lee,Y H Park,W M Sohn,*S T Hong and J Y Chai
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Seoul 110-460, Korea.
Department of Parasitology*, College of Medicine, Inje University, Pusan 614-112, Korea.

The effects of gamma irradiation on the survival and development of C. sinensis metacercariae were studied to evaluate the feasibility of irradiation as a control measure for clonorchiasis. Pseudorasbora parva were collected at an endemic river of clonorchiasis and were used for irradiation of the fluke in three schemes. The first (Scheme 1) was irradiation of the isolated metacercariae from the fish followed by infection to experimental rats. The second (Scheme 2) was irradiation of the fish, and then the metacercariae were isolated and infected to rats. The third (Scheme 3) was irradiation on the rat livers after infection with normal metacercariae. Irradiation doses varied from 5 to 100 Gy for Schemes 1 and 2, and 10 to 25 Gy for Scheme 3. The rats were sacrificed 2 to 6 weeks after infection. In Scheme 1, the metacercariae irradiated at 50 Gy failed to survive in the rats after 2 or 6 weeks. However, 1 to 44% of the metacercariae irradiated at 5-30 Gy survived. The estimated LD50 of Scheme 1 was 16.5 Gy. The flukes irradiated in Scheme 2 survived better than those in Scheme 1. The average worm recovery rate in 50 Gy was 28%(7-39% individually). Increasing the dose up to 100 Gy brought a remarkably low survival rate of an average 1%(0-3% individually). The LD50 of Scheme 2 was 47.5 Gy. Worm recovery rates in the 10 Gy group of Scheme 3 were 21-39%, and those in the 25 Gy group were 2% and 34%. Although the metacercariae were irradiated, all of the recovered worms were morphologically normal.(ABSTRACT TRUNCATED AT 250 WORDS)


Fig. 1
Recovery rate(%) of C. sinensis irradiated on metacercariae or fish, 2 or 6 weeks after infection by gamma-ray dose.

Fig. 2
Survival rate(%) of C. sinensis in logarithmic scale by gamma-irradiation does; irradiation on the metacercariae(mc) or on the fish(fish), arrow heads denote the LD50.

Figs. 1-6
Fig. 1.C. sinensis of the control group, 6 weeks old, ×18.

Fig. 2.C. sinensis from Scheme 3, 10 Gy irradiated on the 9th day after infection, ×18.

Fig. 3. Magnified posterior part of the worm of Fig. 2. The ovary looks well-developed but the testes are poorly-developed and the seminal receptacle is empty, ×40.

Fig. 4.C. sinensis of 30 Gy group irradiated on the metacercariae, ×18. It is morphologically normal.

Fig. 5.C. sinensis, irradiated with 25 Gy on the 9th day after infection, ×18. the ovary, uterus, vitellaria and others are morphologically normal except for the testes and seminal receptacle.

Fig. 6. Magnified posterior end of Fig. 5, with underdeveloped testes and empty seminal receptacle. (Abbreviations; O-ovary, S-seminal receptacle, T-testes, U-uterus filled with eggs)


Table 1
Recovery of C. sinensis from rats infected with irradiated metacercariae (Scheme 1)

Table 2
Recovery of C. sinensis from rats 6 weeks after infection with the metacercariae irradiated in the fish (scheme 2)

Table 3
Recovery of C. sinensis from rats 6 weeks after infection from rats which were irradiated in early stages of infection (Scheme 3)

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