Observations on the life cycle of Davainea proglottina in Britain.

Abstract

1. The life-cycle of the fowl tapeworm Davainea proglottina and its various intermediate hosts are described briefly.2. Studies on the different species of slugs in Great Britain under natural conditions were carried out and a short, simple method of differentiating the species has been presented.3. A satisfactory method of keeping and breeding these slugs under laboratory conditions is described.4. Feeding experiments of the different slugs on freshly collected gravid proglottides confirm that the intermediate hosts, as published by Grassi and Rovelli are as follows: Agriolimax agrestis, Limax cinereus, Limax flavus; by Wetzel, Arion empericorum (A. ater), Arion hortensis, Arion circumscriptus and Arion intermedius. In addition to these known intermediate hosts, the writer succeeded in infecting the following species: Agriolimax reticulatus, Agriolimax carvanae, Milax gracilis and Milax sowerbyi which may accordingly serve under natural conditions as intermediate hosts for D. proglottina.5. The common field or grey slug (Agr. reticulatus) and the garden slug (Arion hortensis) seem to be the most important intermediate hosts for D. proglottina. in Great Britain. Slugs of nearly every age of these two species were experimentally exposed to infection with almost 100% positive results. Both these slugs are the most prevalent and widely distributed species in this country. This fact and the wet climatic conditions which obtain in this country are thus very favourable factors in the propagation of the tapeworm.6. Slugs of different ages were experimentally infected and it was found that younger ones were more susceptible, but Agriolimax reticulatus of almost all ages became infected.7. From the last experiment it may be concluded that slugs will feed on the droppings of fowl despite the presence of a sufficient normal diet, in this case clean lettuce.