A parasitologic survey was made of 990 persons in the city of Cali, Colombia, from whom 1,178 fecal specimens were collected. Stools were examined macroscopically, by direct double cover-glass and by zinc sulfate flotation technics, and in many cases following fixation in MIF medium, on the day they were passed. Attention was focused on E. histolytica, whose prevalence and morphologic character are here reported.
The incidence of infection was 35.5 per cent in 651 inhabitants of one of the wards of the city; 40.3 per cent in 144 patients of a mental hospital; 11.1 per cent in 72 patients in the hospital of the University of Valle; 6.4 per cent in 93 private clinic patients; and 3.3 per cent of 30 fecal specimens from autopsy material.
The incidence tended to be familial since it was significantly higher in 13 selected families than in 99 others, while no positives were found in 21 families. The few trophozoites compared with the number of cysts in the stools suggests a clinically mild infection, due possibly to the large amount of undigested starch in the average stool of the group, which might tend to keep E. histolytica in the large intestine; however, clinical and necropsy evidence indicates that deep and extensive invasion of the tissues may occur, resulting at times in death.
Both a large and a small race of E. histolytica were found in the numerous strains studied. The former averaged 11.8 µ in diameter and contained 1–4 large sausage-shaped chromatoidal bodies; the latter measured most frequently between 6.8 and 7.7 µ and contained several rice-grain chromatoidals. The large race was found four times as often as the small race. The races could also be differentiated by structural characters of the nucleus as well as by cell contents, but there was no evidence that they were separate sepcies, or that the large race was more apt to invade tissues than the small one, under the prevailing conditions.
International Cooperation Administration, Mutual Security Program of the United States Operations Mission to Colombia.