A technique for in vivo labelling of Fasciola hepatica miracidia with radioselenium.

Radioactivity is incorporated in Fasciola hepatica and its eggs when 75Semethionine is administered intraperitoneally in chronically infected mice. Maximum egg-bound radioactivity is achieved 2-3 days after the administration of the labelled aminoacid. Seventy-three per cent of the radioactivity of the egg is recovered in the free-swimming miracidium. There appears to be no altered motility or infectivity to snails of miracidia made radioactive at a level corresponding to 6 pCi per larva. Suggestions are made for the application of labelled larvae in studies on various aspects of the parasite-snail contact.