The infection of laboratory hosts with cercariae of <i>Schistosoma mansoni</i> and the recovery of the adult worms

At present many laboratories throughout the world are studying the chemotherapy and immunology of Schistosoma mansoni in laboratory hosts. Many workers judge the success or failure of their attempts to cure or immunize these hosts from the ratio of the number of living adult worms recovered to the number of infecting cercariae. This ratio is affected, however, not only by the efficacy of any treatment, but also by the methods used to infect the animals and to recover the worms. If these methods result in widely varying worm recoveries amongst the animals in any experimental group, then small but significant effects of treatment might well be missed. Alternatively, such large experimental groups must be used that the work becomes tedious to perform and depends upon the availability of a great deal of technical assistance. This paper describes techniques which are rapid and do not require great skill in their performance. More important, in our hands they have given very consistent results. In this respect, particularly, we believe that these techniques have advantages over others which are currently practised. The techniques described here are those which were used in other investigations reported in this journal (Smithers &amp; Terry, 1965 a, b ). The strain of S. mansoni used throughout this work was isolated in Puerto Rico and was obtained through the courtesy of Dr W. B. DeWitt of the National Institutes of Health. The parasite is maintained in an albino strain of Australorbis glabratus (Newton, 1955). Snails are exposed individually to ten miracidia overnight at 27 °C.