Parasitological surveys in Cali, Departamento del Valle, Colombia VI. Strongyloidiasis in Barrio Siloé, Cali, Colombia

Abstract 1. 1) In connexion with a continuing parasitological survey of a representative sampling of the population in ward Siloe, Cali, Colombia, conducted as part of an epidemiological study of this economically poor community, a special segment of the programme has been concerned with Strongyloides stercoralis infection. This investigation included 92 families comprising 982 persons. Freshly-passed faecal specimens were examined macroscopically and microscopically for intestinal parasites, employing unstained and iodine-stained direct faecal films supplemented by zinc sulphate concentration preparations. 2. 2) A total of 2974 stools were examined from November, 1956, through April, 1959. One hundred and thirty-seven (14 per cent.) of the 982 individuals were found positive for Strongyloides . One hundred and six were first diagnosed from the first specimen submitted, 20 were first diagnosed from the second specimen, seven from the third sample, and four from the fourth. Subsequent samples provided no additional first positives. 3. 3) The zinc sulphate centrifugal floation technique proved to be 50 per cent. more efficient than the double cover-glass direct films in discovering Strongyloides larvae. 4. 4) One or more persons in each of 62 of the 92 families were found to be infected, by the techniques employed. The number of positive persons per family varied from one to nine. 5. 5) Appreciable infection (4.8 per cent.) occurred before 5 years of age, after which time the incidence rate rose rapidly during the next quinquennium, maintained this level for three decades, rose again in the fourth decade, remained high in the males and rapidly declined in the females. The incidence per cent. was consistently higher in the males than in the females after the first 5-year period. 6. 6) Environmental conditions and low-grade personal hygiene are conducive to exposure to infective-stage Strongyloides on the moist dirt floors of the houses of the community. Autoinfection may play a significant role in maintaining the infection once it has become established. 7. 7) There is no evidence that strongyloidiasis in ward Siloe is a severe debilitating disease; rather it appears to be a chronic parasitosis which is fairly well tolerated.