Exposing Oncomelania snails to Schistosoma japonicum miracidia

 

Author Yung-san Liang

 

Introduction

S. japonicum miracidia penetrate readily into the tissues of Oncomelania snails, as do S. mansoni and S. haematobium miracidia into their respective snail hosts.

 

Equipment

Dissecting microscope

 

Materials and reagents

Aged tap water

Petri dish (preferably 60 mm in diameter)

Fine-tip (drawn) pasteur pipette

Algae and diatoms

 

Procedure

·         For best results, all 4 subspecies of Oncomelania discussed here should be exposed to miracidia once they have reached about ½ the length of their eventual size. O.h.quadrasi should be exposed at no less than 3 mm in length, whereas O. h. nosophora, O.h.hupensis, and O.h. formosana should be exposed at no less than 4 mm in length. 

·         Place the snails in a 60 mm petri dish with a minimal volume of aged tap water

·         Using a dissecting microscope and a drawn pasteur pipette, aspirate a pre-determined number of free-swimming miracidia and add to the snails in the dish.

·         Snails should be exposed to an average of 10 miracidia per snail for at least two hours. Mass or individual exposures of Oncomelania (as in the S. mansoni/B. glabrata system) can be used.

·         After exposure, snails should be placed into a tray with algae and diatoms, and the tray changed once a week. Fifty-to-100 snails can be maintained per tray.

 

Follow-up comments/recommendations

The percentage of snails developing a patent infection (with its corresponding geographic strain of parasite) with the above procedure is about 50%. The exception to this is O.h.hupensis, 70% of which can develop patent infections.

 

References

Liang, Y-S., Bruce, J.I., and Boyd, D.A. 1987. Laboratory cultivation of schistosome vector snails and maintenance of schistosome life cycles. Proceedings of the First Sino-American Symposium 1: 34-48.