Date of Award:


Document Type:


Degree Name:

Master of Science (MS)



Department name when degree awarded

Arts and Science

Committee Chair(s)

D. M. Hammond


D. M. Hammond


Parasitic protozoa of the intestinal tract of man were first observed by Anthony van Leeuwenhoek (1632-1723), a Dutch microscopist. In the year 1681, while observing his own excrement, Leeuwenhoek discovered and described certain forms of life which he called "animalcules" and which were verified later by workers in protozoology as Giardia lamblia, a protozoan parasite of the intestinal tract. During the period preceding the later part of the 19th century many observations of the parasitic intestinal protozoa of men and lower animals were made and many species were classified. It wasn't, however, until the year 1875 that a protozoan of the human intestine was observed to be pathogenic. Loesch, in this same year discovered the protozoan Endameba histolytica in the feces of a Russian peasant who was suffering from dysentery; and although he did not regard the organism as the cause of the symptoms, it was supposed by many authorities that the cause of dysentery was directly due to this organism. In the year 1913 all doubt as to the pathogenicity of this amoeba was erased when two American protozoologists, Walder and Sellards, demonstrated by experiments upon human volunteers the Endemeba histolytica was the cause of amoebic dysentery. The work of these two men confirmed results of workers such as Ostler, Kartulis, Councilman and LaFleur. It was also in 1913 that Walder and Sellards proved, through experiments on human patients, that a closely related form, Endameba coli, was a harmless commensal of the intestinal tract. The cyst forms of these organisms were discovered in 1893 by Quinke and Roos, while Huber in 1903 made accurate descriptions of this stage in the life cycle of these organisms. It has only been within the last 20 years that intestinal protozoa have been cultured successfully outside of the human body. This has added greatly to the understanding of the life cycles, growth, and reproduction of these organisms; and it has consequently increased the knowledge of treatment of intestinal protozoa infestation.