Kozen Yoshino's experimental infections with Taenia solium tapeworms: An experiment never to be repeated

In the 1930's Kozen Yoshino published 6 papers on Taenia solium. One of these papers is particularly important because it describes the outcomes of experimental infections with T. solium tapeworms in four volunteers, Yoshino being one of them. The paper was written in an old form of the Japanese language, making it almost inaccessible to most researchers around the world. Here we provide a non-literal translation of this work and some brief comments by the translators. Each of the four volunteers swallowed three or five cysticerci recovered from an experimentally infected pig. Each person was found to have harbored 2 - 5 tapeworms when the infections were terminated by drug treatment between 120 and 451 days after infection. The pre-patent period recorded by Yoshino's volunteers was between 62 and 72 days based on the first appearance of gravid proglottids (GPs) in the feces. In one subject, the number of GPs appearing in each bowel movement was tracked daily for 371 days following the first appearance of GPs in the feces, together with the number of bowel movements each day. GPs were observed on 275 of the 284 days on which the subject defecated during which observations were made. There was a decline in the number of GPs over the observation period; proglottids were observed on 97% of all days on which defecation occurred, they were present on 87% of days in the last month of infection. The cumulative number of GPs for a month in the 1st, 6th and 12th months of patent infection was 334, 174 and 126, respectively.