Studies on intestinal trematodes in Korea XIV. Infection status of loaches with metacercariae of Echinostoma cinetorchis and their development in albino rats
Byong-Seol Seo,Yang-Hee Park,Jong-Yil Chai,Sung-Jong Hong and Soon-Hyung Lee
Department of Parasitology and Institute of Endemic Diseases, College of Medicine, Seoul National University, Seoul 110, Korea.
The metacercariae of Echinostoma cinetorchis (Trematoda: Echinostomatidae) were found infected in the loaches (Misgurnus anguillicaudatus) purchased from two local markets in Korea. Identification of the metacercariae was done after obtaining adult worms from experimentally infected albino rats. Brief course of worm development in rats was also observed up to 28th post-infection day. The results are as follows: The metacercariae of E. cinetorchis were detected from 5 (10.9 percent) out of 46 loaches examined and the average metacercarial burden per infected loach was 34.4. They were always found from the posterior abdominal wall. The worm recovery rate from 8 rats was 24.6 percent in average. It was observed that the rate decreased according to age of infection; from 40.7 percent after 6 days to 15.0 percent after 28 days. The adult worms were morphologically characterized by the presence of head crown with dorsally uninterrupted collar spines, 37-38 in number, and the tendency of migration or disappearance of testes. So that they were identified as Echinostoma cinetorchis Ando et Ozaki, 1923. The development of worm was very rapid during 6-10 days after infection and became much slower thereafter. During the rapid worm growth the development of genital organs was more prominent than that of non-genital organs. From the results it is concluded that the loach is involved in the life cycle of E. cinetorchis in this country and may take a role for infection source to animals and man. It is also confirmed that migration or loss of testes is the distinct specific character of this echinostomatid fluke.
Figs. 1-4 Fig. 1. Metacercariae (arrow) of E. conetorchis in posterior abdominal wall of the loach, Misgurnus anguillicaudatus. ×40.
Fig. 2. Higher magnification of Fig. 1. ×100.
Fig. 3. Isolated metacercaria of E. conetorchis which shows well developed oral sucker (OS), ventral sucker (VS), refractile excretory granules (Ex) and end group spines (S). ×400.
Fig. 4. 6-day old juvenile worm of E. conetorchis showing ovary (O), Mehlis' gland (MG) and coiled uterus (U) which does not contain eggs.
** Scale unit in Fig. 4 is millimeter.
Figs. 5-8 Fig. 5. 10-day old adult worn. The rosette form uterus with numerous eggs and the witelline follicles have developed well.
Fig. 6. An adult worm recovered on 16th day after infection showing two testes (T), one of which noved to the postero-lateral portion of ventral sucker.
Fig. 7. 21-day old adult worn.
Fig. 8. 28-day old worn. Note that the number of intra-uterine eggs narkedly decreased and testes disappeared.
** Scale unit in Fig. 5-8 is millimeter.
Fig. 9 Growth curves of body length and width according to age of worms.
Fig. 10 Growth curves of non-genital organs according to age of worms.
Fig. 11 Growth curves of genital organs according to age of worms.
Table 1 Infection status of the loach, Misgurnus anguillicaudatus with the metacercariae of E. conetorchis
Table 2 Recovery rate of E. conetorchis form albino rate after experimental infection
Table 3 Measurement of E. conetorchis recovered from the experimentally infected albino rats
Table 4 Number and location of testes according to infection age of E. conetorchis in rats
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