T. intestinalis, R. Leuckart, appears to be capable of settling in all parts of the human intestine in which the contents have an alkaline reaction. Trichomonads have been cited as occurring in the oral cavity by Steinberg, Zunker, Rappin and Prowazek; in the œsophagus by Cohnheim, and in the stomach by Strube, Cohnheim, Zabel, Hensen and Rosenfeld. The normal situation seems to be the small intestine. The parasites then appear in the dejecta, especially in various intestinal diseases the course of which is connected with an increased peristalsis. They are also found in healthy persons, from whom they are obtained after the administration of laxatives. They have been regarded by some workers as commensals, which, however, have the power of accelerating the onset of intestinal complaints, or at least of adding to them. They have been found in cases of carcinoma of the stomach, and in other diseases of that organ in which the acid reaction ceased.
Naturally, whether all the reports relate to the same species of Trichomonas must remain undecided. Certain authors (Steinberg, Cohnheim, van Emden) accept several species. Prowazek speaks of a variety of T. intestinalis inhabiting the oral cavity. This was distinguished by a posterior process exceeding the length of the body fourfold, and by a somewhat unusual course of the undulating membrane. The food of this form, which was found in the whitish deposit present, especially in the cavities of carious teeth, consisted almost exclusively of micrococci. Schmidt and St. Artault named the Trichomonads found in pathological products (e.g., gangrene, putrid bronchitis, phthisis) of the lungs of man, as Trichomonas pulmonalis. Trichomonads have also been found by Wieting in lobular pneumonia in the lungs of pigs.
It is still uncertain in what way the infection takes place. Experiments in the transmission of free trichomonads to mammals (per os), in which the same or allied species occur (guinea-pigs, rats, apes), have been without result. Probably encystment is necessary. Such conditions are mentioned by May, Künstler, Roos, Schurmayer, van Emden, Prowazek, Galli-Valerio and Schaudinn. According to Prowazek, intestinal trichomonads of rats become encysted for conjugation. In the cyst an accumulation of reserve food material occurs, causing distension. The nuclei of the conjugants each give off a reduction body and, after fusion, produce the nuclei for the daughter individuals. According to Schaudinn the intestinal trichomonads lose their flagella before conjugation, become amœboid and encyst in twos, the formation of a large agglomeration of reserve substance accompanying this. Galli-Valerio found double-contoured cysts in the fæces of trichomonad-infected guinea-pigs, after the fæces had been kept for a month in a damp chamber. When exposed to heat small flagellates escaped from them. Administration of such material containing cysts resulted in severe infection with trichomonads, and death of the experimental guinea-pigs followed. The cyst wall is clearly a protection against the deleterious acid reaction of the stomach contents. Alexeieff (1911) and Brumpt (1912) think that the trichomonad cysts of man are really fungi, while other workers also doubt encystment among trichomonads. Wenyon (1907) states that T. intestinalis in mice produces spherical contracted forms which escape from the body in the fæces.
Air, water, and under certain circumstances even food may be regarded as vectors for the trichomonads. The occurrence of the organisms in the oral cavity, and still more so in the lungs, is in favour of the air being the transmitting agent. An observation made by Epstein supports the idea of water transmission. Multiplication of the trichomonads, once they have gained access to the body, is effected by longitudinal division commencing at the anterior end (Künstler). “Cercomonads” with several flagella and an undulating membrane, as well as trichomonads, have been observed by Ross in some cases of cutaneous ulcers.
Mello-Leitao (1913)41 has described flagellate dysentery in children in Rio de Janeiro. He states that it is due to T. intestinalis and Lamblia intestinalis either separately or together. Flagellate dysentery, he thinks, is benign and is the most frequent form of dysentery in infants. The flagellates are pathogenic to infants under three years of age. Escomel (1913)42 found 152 cases of dysentery in Peru due solely to Trichomonas. Such cases are probably widespread.
Genus. Tetramitus, Perty, 1852.
Tetramitus mesnili, Wenyon, 1910.
Syn.: Macrostoma mesnili, Chilomastix mesnili, Fanapapea intestinalis.
The genus Tetramitus differs from Trichomonas in possessing an undulating membrane inserted in a deep groove or cytostome. There are three anterior flagella. The pear-shaped organism measures 14 µ by 7 µ, but smaller examples occur. T. mesnili occurs in the human intestine, having been described by Wenyon43 (1910) from a man from the Bahamas in the Seamen’s Hospital, London. Its occurrence is widespread. Alexeieff considers that Macrostoma and Tetramitus are synonymous. The parasite is the same as Fanapapea intestinalis, Prowazek, 1911, from Samoa. Brumpt (1912) found T. mesnili to be the causal agent of colitis in a Frenchwoman. Nattan-Larrier (1912) considers it of little pathological importance.
Gäbel44 (1914) described an interesting case of seasonal diarrhœa acquired in Tunis, in which a new Tetramitid was the causal agent. The organism was pear-shaped, without an undulating membrane, and measured 6·5 µ to 8 µ by 5 µ to 6 µ. The cytostome was large, and there was no skeletal support. Encystment occurred. Gäbel named the organism Difämus tunensis and considered that it was pathogenic.
Genus. Lamblia, R. Blanchard, 1888.
Syn., Dimorphus, Grassi, 1879, nec Haller, 1878; Megastoma, Grassi, 1881, nec de Blainville.
The body is pear-shaped, with a hollow on the under surface anteriorly. It has four pairs of flagella directed backwards, of which three pairs lie on the borders of the hollow disc, and the fourth arises from the pointed posterior extremity.
Lamblia intestinalis, Lambl, 1859.
Syn.: Cercomonas intestinalis, Lambl, 1859 (nec 1875); Hexamitus duodenalis, Davaine, 1875; Dimorphus muris, Grassi, 1879; Megastoma entericum, Grassi, 1881; Megastoma intestinale, R. Blanch., 1886; Lamblia duodenalis, Stiles, 1902.
The organism is pear-shaped and bilaterally symmetrical. It is from 10 µ to 21 µ long and 5 µ to 12 µ broad and possesses a thin cuticle. Anteriorly an oblique depression is present, which functions as a sucking disc (fig. 19, s). Its edges are raised above the general surface and are contractile. It corresponds to a peristome and acts as an adhesive organ (fig. 20, b, c). No true cytostome is present. A double longitudinal ridge, representing axostyles, extends from the sucking disc to the tapering posterior extremity, which is prolonged as two flagella from 9 µ to 14 µ long.
Lamblia intestinalis possesses eight flagella (fig. 19). The first pair of flagella, which cross one another, arise in a groove formed by the anterior edge of the sucking disc. Two pairs of flagella (lateral and median) are inserted on the posterior edge of the disc, while the posterior flagella occur at the tapering posterior extremity of the body. Basal granules are found at the bases of the flagella. The median flagella are most active in movement, the anterior and lateral flagella being less motile, as they are partially united to the body for part of their length.
The nuclear apparatus is situated in the thin, anterior, hollowed part of the body. It is at first dumb-bell shaped, the “handle” of the dumb-bell being formed by a very slight connecting strand, which eventually separates, so that the flagellate becomes binucleate, and thus completes