Some Experiments and Observations on the Longevity of Diphyllobothrium Infections

Abstract

In an article on “The Longevity of Diphyllobothrium latum” published in 1935 in the “Recueil des Travaux dédié au 25-me Anniversaire Scientifique du Professeur Eugène Paviosky 1909−1934”, it is suggested that present day conceptions regarding the longevity of this parasite are erroneous and that multiple successive infections are frequently attributed to a single long-lived specimen. Ward gives a detailed review and analysis of the evidence hitherto published both in general works and special monographs and cites as specially important the history of the occurrence of this species on the North American continent. He points out that the age of the parasite is regularly based on the statement that the host had not been in an infected region for the period indicated. To this statement, Ward puts forward the objections that the distribution of the parasite and the natural occurrence of plerocercoid carrying fish are far more extensive than was formerly suspected and, further, that infected fish are distributed commercially as food to regions far outside their natural area of distribution. He also refers to certain records which seem to indicate that there is a “period of inactivity” during the adult life of the parasite and suggests that its alleged occurrence throws doubt upon the supposed longevity of the parasite. In support of this contention, he cites, as a typical instance, a case of human infection with Diphyllobothrium latum reported by me (Leiper, 1928) as a “cryptic infection”; regarding which he erroneously states that I believed was “latent” for 5 years.