Comparative morphology of eggs of heterophyids and Clonorchis sinensis causing human infections in Korea

Abstract

In order to provide some clues for differential diagnosis of trematode infections in fecal examination, the comparative morphology of eggs of 5 kinds of heterophyid flues (Metagonimus yokogawai, Heterophyes heterophyes nocens, Heterophyopsis continua, Stellantchasmus falcatus and Pygidiopsis summa) and Clonorchis sinensis was studied. The eggs were obtained from distal portion of uteri of worms which were recovered from men after treatment. The characteristic shape and appearance of each kind of eggs were observed in detail under light microscope, and their length and width measured and compared one another. The results are as follows: Eggs of C. sinensis are elongated ovoidal in shape with attenuated anterior end, 25.3~33.2 (28.3 in average) μm long and 14.2~17.4 (15.9) μm wide with length/width ratio of 1.60~2.00 (1.78). They differ from all heterophyid eggs in that they have prominent wrinkling (muskmelon pattern) at their shell surface. P. summa eggs are ovoid to pyriform in shape and characterized by the smallest size of all kinds examined, 19.8~22.9 (21.6) μm long and 11.1~13.4 (12.1) μm wide and the ratio 1.63±1.99 (1.78). Eggs of S. falcatus are elongated ovoidal and most slender form, 25.3~29.2 (27.2) μm long and 11.1~13.4 (12.5) μm wide with the ratio of 2.00~2.57 (2.17). Eggs of M. yokogawai are ellipsoid to elliptical in shape with round both ends, 26.9~31.6 (28.5) μm long and 14.2~18,2 (16.8) μm wide with the ratio of 1.48~2.11 (1.70). H. continua eggs are oval in shape, sometimes similar to M. yokogawai or H. h. nocens eggs, however, the relative breadth is broadest among all kinds, with maximum width at posterior half portion. They are 23.7~27.7 (25.0) μm long, 15.8~18.9 (16.4) μm wide with the ratio of 1.33~1.75 (1.53). Eggs of H. h. nocens are ellipsoid to ovoid in shape but sometimes more slender than M. yokogawai and have slightly pointed both ends. They are 23.7~29.2 (25.7) μm long, 14.2~15.8 (15.4) μm wide, and the ratio 1.50~2.06 (1.67). From the results, it is concluded that eggs of 5 kinds of heterophyids and C. sinensis can be morphologically differentiated one another, however, careful observation and measurement on sufficient number of eggs are needed.