RESUMO
Animal models have been utilized to study experimentally produced intestinal amebiasis. The guinea pig has been the animal of choice to study the mechanisms by which trophozoites of E. histolytica produce colonic lesions. The purpose of this study was to produce lesions in the colon of newborn guinea pigs by the injection of E. histolytica, HM-1 IMSS, strain grown axenically, and to characterize the early changes with the light and electron microscopes. A total of 35 guinea pigs, one to two days old, were inoculated into the cecum with one and a half million of trophozoites of E. histolytica. Thirteen surviving animals were sacrificed. In four there were clear cut amebic lesions. Sections were taken from neighbouring transitional zones. The most important changes were the migrations of trophozoites to the bottom of colonic glands with many parasites located within the crypts. There was passage of ameabae to the lamina propia with practically no inflammatory reaction. It is thought that the parasite, in contact with epithelial crypt cell, produce direct lysis of these elements leading to migration of amebae into the lamina propia.