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Cross Infectivity Study of Four Subspecies of Oncomelania hupensis in Four Geographical Strains of Schistosoma Japonicum

Published: | Vol 16, Issue 2 (1983)

Authors

Abstract

. Four subspecies of Oncomelania hupensis, namely O.h.lindoensis, O.h.hupensis, O.h.nosophora and O.h.quadrasi were exposed to miracidia of four different geographical strains of Schistosoma japonicum, i.e.: the Chinese, Japanese, Philippine and lndonesian strains. Result of this experiments showed that O.h.lindoensis from Indonesia and O.h.hupensis from China found to be the most susceptible for all geographical strains of S.japonicum while O.h.quarasi from the Philippines was the most refractory and could only be infected with the Philippine strain. Sari. Empat subspecies Oncomelania hupensis: O.h. lindoensis, O.h. hupensis, O.h. nosophora, dan O.h. quadrasi telah dicoba diinfeksikan di dalam laboratorium dengan miracidia dan berbagai strain Schistosoma japonicum. Strain S. japonicum yang dipakai untuk menginfeksi keempat subspecies O. hupensis tersebut adalah strain Cina, Jepang, Filipina dan Indonesia sendiri. Hasil percobaan ini menunjukkan bahwa O.h. lindoensis dari Indonesia dan O.h. hupensis dari Cina ternyata paling tidak rentan dan hanya dapat diinfeksi oleh S. japonicum dari strain Filipina sendiri.

SARI

Empat subspecies Oncomelania hupensis: O.h. lindoensis, O.h. hupensis, O.h. nosophora, dan O.h. quadrasi telah dicoba diinfeksikan di dalam laboratorium dengan miracidia dari berbagai strain Schistosoma japonicum.

Strain S. japonicum yang dipakai untuk menginfeksi keempat subspecies O.hupensis tersebut adalah strain Cina, Jepang, Filipina dan Indonesia sendiri.

Hasil percobaan ini menunjukkan bahwa O.h. lindoensis dari Indonesia dan O.h. hupensis dari Cina tempata paling rentan terhadap infeksi keempat strain S. japonicum, sedangkan O.h. quadrasi paling tidak rentan dan hanya dapat diinfeksi oleh S. japonicum dari strain Filipina sendiri.

1. INTRODUCTION

The intermediate host of Schistosoma japonicum in the Lindu Valley, Central Sulawesi, Indonesia, was discovered in 1971 (Carney et.al. 1973) and described as a new subspecies of Oncomelania, namely Ohupensis lindoensis by Davis and Carney (1973). Subsequent epidemiological surveys deleniated more than 70 snail foci in the lowlands surrounding Lake Lindu (Sudomo and Carney, 1974; Sudomo et.al., 1978) and the natural infection rates of S. japonicum in a variety of oncomelanid habitats throughout the valley (Sudomo et.al., 1978). Transmission of Oriental schistosomiasis was only found in two limited areas of

*) Part of Dessertation at LFB, Promotor Prof Dr. D.A. Tismamidjaja, co-Promotor Dr. H.P. Striebel and Dr. S. Sastrodihardio.

**) National Institute of Health Research and Development, Jl. Percetakan Negara 1, P.O. Box 226, Jakarta, Indonesia.

Central Sulawesi, the Lindu and Napu valleys (Sudomo and Carney, 1974; Carney et.al., 1977). The evolution and zoogeography of both snails and schistosomes in those isolated areas of Central Sulawesi is discussed in detail elsewhere (Davis 1979; 1980). Several distinct geographical strains of S. japonicum and different subspecies of O.hupensis occur throughout Asia and information on the degree of genetic relationship between strains and between subspecies can be obtained from cross infection studies. Although there have been several reports of heterologous and homologous experimental infection of S. japonicum and O. hupensis subspecies (De Witt, 1954; Hunter, Richi and Otori, 1952; Pesigan et. al., 1958; Moose and Williams, 1963, 1964; Hsu Hsu, 1960; Chiu, 1967; Chi et. al., 1971; Davis and Ruff, 1973 and Rachford, 1977), experimental infection utilizing the Indonesian strain so far was done only by Cross (1976).

The purpose of this present cross infection studies of each of the four subspecies of Oncomelania snails namely: O.h. lindoensis, O.h. hupensis, O.h. nosophora and O.h. quadrasi to miracidia of four different geographical strains of S. japonicum i.e. the Chinese, Japanese, Philippine and Indonesian were to find out the degrees of susceptibility of these snails subspecies in relation to the various strains of schistosome.

2. MATERIAL AND METHODS

The snails used in these experiments were obtained from laboratory colonies, except for O.h lindoensis, which were collected from Lake Lindu area, Indonesia. Field collected O.h. lindoensis were checked for cercariae several times at two weeks interval by a shedding technique (Vogel, 1948) and were found negative. Other subspecies of O.h. hupensis used in this study: O.h. hupensis which had been isolated by Vogel in the province of Chekiang in 1935 (Vogel, 1948), was maintained in breeding colonies kept in the laboratories of Ciba Geigy (Trop. Med. Parasitology Laboratory); O.h. quadrasi was obtained from the field (Leyte, the Philippines) by Santos and was set up as a laboratory colony by Striebel in 1963; O.h. nosophora isolated by Okabe in 1972 and maintained as a laboratory colony in Sandoz laboratory in Wien.

The Indonesian strain of S. japonicum was isolated during this study from infected snails collected in Lindu valley. The Philippine and Japanese strains were obtained from experimentally infected mice from the NAMRU-2 laboratory in Taipei, Taiwan, and the Chinese strain was obtained from the Ciba Geigy laboratory in Basel.

Miracidia of the Philippine and Japanese strains of S. japonicum were obtained by a hatching technique (Striebel, pers. comm. 1976), using eggs recovered from the stool, liver and intestines of mice; the Chinese strain was obtained from the liver and intestines of hamsters; and the Indonesian strain from the stool of a beagle dog.

The snails were exposed singly to 3 to 4 newly hatched miracidia for one hour in a vial of \(1.5 \times 7\) cm. The exposed snails were then kept in an aquaria under controlled laboratory conditions at constant temperature (\(25^{\circ} \pm 1^{\circ}\)C), Rh 75% under "cold" fluorescence light (GRO-Lux 40 watts) during the day. After an interval of five weeks, the snails were checked for infection once weekly for five consecutive weeks by the shedding technique according to Vogel (1948). All snails which were negative after 5 successive shedding were crushed.

3. RESULTS AND DISCUSSION

The cross infection results (Table 1) showed that all the four strains of S. japonicum developed in O.h. lindoensis with relatively high positive rates. Although O.h. hupensis was shown to be susceptible to all four strains of S. japonicum, infection rates with the Philippine and Japanese strains of S. japonicum were much lower than with the Indonesian and Chinese ones. Oncomelania h.nosophora was susceptible to the Philippine and Japanese strains of S. japonicum but infection rate with the homologous strains of S. japonicum was much lower than with the Philippine strain. O.h. quadrasi was only susceptible to its homologous strain of S. japonicum.

It has long been established that the survival of geographic strains of schistosome depends on their success to penetrate and develop in snail hosts of very specific genotypes within the species (Basch, 1976; Davis, 1979, 1980; Moose and Williams, 1963; Chiu, 1967 and De Witt, 1954). As an example the Japanese strain of S. japonicum will develop in O.h. nosophora, in O.h. hupensis from Mainland China, and in O.h. chiui from Tajwan, but not in O.h. formosana from Southern Taiwan nor in the Philippine snail O.h. quadrasi (Davis and Ruff, 1973). In the present study, the four strains of S. japonicum develop in the Indonesian and Chinese snails (Table 1). The low infection rates of O.h. hupensis with the Philippine and Japanese schistosome were in agreement with those of Chi et.al. (1971), De Witt (1954) and Hsu Hsu (1960) but with the homologous Chinese schistosome, the present study showed a much higher rate than that of Chi et. al. (1971) and De Witt (1954). Cross (1976) exposed O.h. quadrasi to the Indonesian schistosome and found it is to be refractory. Chi et. al. (1971) showed this snail could be infected by its own parasite, but not with the schistosomes of the Chinese and Japanese strains.

The results of this study (Table 1) and those of Chi et. al. (1971), Cross (1976) and De Witt (1954) confirmed that O.h. quadrasi is very parasite-specific and could only be rnt'ected by the homologous strain of S. japonicum which naturally infect humans.

Trblc l. Cross infection between four different geographical strains of Schistosona jdpotrt.zm in four subspecies ofOncttmebnio hupensis.

0tcomelub
hupensis		Straln of
S. Japonicum		No. of snafl
exposed		Survftd ten
weeks after
exposure (%)		Infection of
survivals (%)
Indonesian26672.228.6
IindoensisPhdippine5 784.260.4
(lndonesia)Chinese19617.341.0
Japanese4245.231.6
llupe"td
(China)		Indonesiant6284.067.0
Philippine8062.s4.0
Chinese32093.450.0
Japanese1 593.33.0
qudrasi
(Philippine s)		lndonesianlsl7 6.80
Philippine8093.846.'7
Chinese5682.10
Japanese6382.50
nosophoraPhilippine2588.036.3
(Japan)Japanese4580.02.7

However, tlte O.h.qtadrasi was weakly susceptiblc to thc zoopliilic Formosan strain of S. japonicum (6.4%) (De Witt, 1954). O.h. nosophora, when exposed to the Philippine and Japanese schistosomes. was susceptible to both these strains but the infection rate with hornologous strain of S. japonicunl was very low (2.7%) when compared to the Pliilippine strain (36.3%). O.h. nosophora was not exposed to ttre other two strains of schistosome in the present study, but Chi €t. dl. (197 | ) and De witt ( I 954) in their studies found O.l,. nosophora refractory to the Chinese strain, but susceptible to S. japonicutn of the Philippine and Japanese strains (Moose and Willtams. 1963; De Witt 1954; Hunter, Ritchi and Otori, 1952; Davis and Ruff, 1973 and Chi et.d/., l97l). Moose and Williams (1963) demonstrated that O-h. fonnosana from three different areas of Taiwan when exposed to S. japonicum had infection rates rangin{from 0ol, to 957o. The different degrees of infection rates in O.lz. nosophora with its own parasite of 2.1% in the present findings as compared to 33.3o/" obtained by Chi et. al. (197ll could probably be attributed to the observations made by Moose and Williams (1963), or by the small number of O.h. nctsophora exposed with the narasite

The survival rates of the various subspecies of oncomelanids exposed to geographical strains of S japonicum were usually more than 60%, however, when O.h. lindoensis was exposed to the Chinese strain of S japonicum the mortality was relatively high (82.7%). Similarly high survival rates in cross infection experiments was reported by Cross et al (1976) and Chi et al. (1971).

SUMMARY

Studies on cross infection between four geographical strains of S. japonicum in four subspecies of O.h. hupensis had been carried out. Results showed that the Indonesian strain, O.h. lindoensis, and the Chinese strain, O.h. hupensis, were the most susceptible subspecies to the four strains of S. japonicum, i.e. the Chinese, Japanese, Philippine and Indonesian. The Philippine strain, O.h. quadrasi, was the most refractory and could only be infected with the homologous strain of S. japonicum. While the Japanese subspecies, O.h. nosophora, exposed to the Philippine and Japanese only, was found to be susceptible to both strains of S. Japonium.

ACKNOWLEDGEMENTS

The author wishes to thank Dr. W. P. Carney from NAMRU-2 for providing the Philippine and Japanese strains of S. japonicum and to Dr. H. P. Striebel, Head, Trop. Med. Parasitology Laboratory, Ciba Geigy, Basel, Switzerland for his support and access to material and equipment for this study.

References

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