THE INTESTINAL PROTOZOA OF THE GUINEA-PIG

Resumen

1. The present study was carried out in connection with an investigation of experimental amebiasis in the domestic guinea-pig, in which Endamoeba histolytica of human origin was used as inoculum.
2. The domestic guinea-pig (Cavia cobaya) is generally considered to have been derived from C. porcella of Brazil. It has been under domestication in Europe since the early part of the sixteenth century and is almost universally bred as a household pet and for laboratory experimentation. Closely related extant species are the wild guinea-pig or preá (C. aperea), of Brazil, and the domesticated C. cutleri, of Peru.
3. A considerable number of protozoa and several species of helminths have been described as natural parasites of the genus Cavia. In an examination of the intestinal feces of the animals in an experimental amebiasis series a number of protozoa have been encountered and studied. This lead to a survey of the literature to correlate the present observations with those of previous investigators. A review has been prepared which includes all of the species of protozoa described from the intestinal tract of the several species of Cavia.
4. The list of natural protozoan parasites of the intestinal tract of the guinea-pig includes the following:
RHIZOPODA. - Endamoeba cobayae, Endolimax caviae.
MASTIGOPHORA. - Chilomastix intestinalis, Trichomonas caviae, T. flagelliphora, Eutrichomastix caviae, Enteromonas caviae, Embadomonas intestinalis, Oikomonas termo, Sphaeromonas communis, Spiromonas angusta (reported for the first time from the guinea-pig), Globomonas parasitica, Chilomitus caviae, Monocercomonas caviae, Selenomonas ruminantium, Giardia caviae.
CILIA TA. - Balantidium caviae, Cyathodinium vesiculosum, C. conicum, C. piriforme, Enterophrya elongata, E. piriforme, Cunhaia curvata.
SPOROZOA. - Eimeria caviae.
5. Several of the described protozoa are native to C. porcella and C. aperea in Brazil, even though some of them were first reported from C. caviae in other parts of the world. A few are also parasitic in the intestine of other rodents closely related to the guinea-pig, as the agouti, capybara, mara and paca. Some of these protozoa have previously been reported from ruminants, which are probably their natural hosts. A number of the protomonad flagellates are coprophilic in their biology and are only fortuitously facultative inhabitants of the intestinal tract of the guinea-pig or any other animal.
6. Except for Eimeria caviae, which is described from the wall of the large bowel of the guinea-pig, and Balantidium caviae, which is capable of invading the cecal mucosa but apparently produces no appreciable inflammatory reaction, none of the species of protozoa described from the intestine of the guinea-pig are tissue
invaders and none are of pathologic importance.
7. The guinea-pig has been found to be highly susceptible to infection with Endamoeba histolytica of human origin. In 33 of 35 inoculated animals typical amebic lesions were demonstrated in the cecal wall, in most instances with colonies of amebae in the lesions. In one of the other two animals amebae were found in the lumen feces but not in the tissues, while in the remaining animal, which died a few hours before it was to be sacrificed and was not studied in histologic section, a large number of active E. histolytica were found in the contents of the cecum and ascending colon.