In many instances the existence of a tapeworm may not cause any inconvenience to its host, and its presence may be only made.
Of cases the entire tapeworm is expelled.
For twelve hours previously to its administration no food should be given, in order that the intestinal tract should be empty so as to expose the tapeworm to the full action of the drug.
Whether this view is soundly based is discussed below; the fact remains, however, that a tapeworm is, with few and rare exceptions, not directly comparable at all points with a liver-fluke or indeed with any other organism.
The occurrence of the broad tapeworm in man is often associated with anaemia of a most severe type.
- For practical purposes we have only three varieties of tapeworms to deal with as inhabitants of the human alimentary canal: Taenia saginata, the beef tapeworm; Taenia solium, the pork tapeworm; and Dibothriocephalus latus, the fish tapeworm.
The first of these is prevalent in countries where much and imperfectly cooked beef is eaten, and where cattle in their turn are exposed to the infection of the tapeworm ova.
In North Germany the mature tapeworm was found on post-mortem examination once in every 200 bodies examined, while its embryo, the Cysticercus cellulosae, was found in in every 76 bodies.
Unlike the tapeworm no intermediate host is required for the development of this worm.
This fact gave rise in ancient times to the false idea that the tapeworm originated from the union of these segments; and in modern times it has led to the view that the tapeworm is not a segmented organism (the monozoic view), but is a colony composed of the scolex which arises from the embryo and of the proglottides, which are asexually produced buds that, upon or before attaining their full size and maturity, become separated, grow, and, in some cases, live freely for a time, just as the segments of a strobilating jelly-fish grow, separate and become sexual individuals (the polyzoic view).
The tapeworm, Taenia saginata, throws off eleven proglottides a day during its mature stage, and if this rate of increase were maintained for a year the total weight of its progeny would be about 550 grammes.
The tapeworm most frequently found in man in Western Europe is the Taenia solium, which is constant wherever pork is consumed, and is more common in parts where raw or imperfectly cooked pork is eaten.
Mention is made under Tapeworm of the worms of that species inhabiting the human body as parasites, and it will be convenient here to mention other parasitic varieties.