Intestinal parasitic infections in an institution for the mentally retarded.

Of 550 mentally retarded patients in an Italian institution, 125 (23%) were found to be infected with intestinal parasites. The infections were most frequent in young men, those with severe mental retardation, the chronically institutionalized and those living in older wards. Ninety-four (75.2%) of the parasitised subjects were infected only with protozoa, 25 (20%) only with helminths, and six (4.8%) with protozoa and helminths. Entamoeba histolytica and E. dispar infections were detected, but at low prevalences; in-vitro culture in Robinson's medium and isoenzyme electrophoresis of the cloned amoebic isolates indicated one infection with E. histolytica (zymodeme XII) and two infections with E. dispar (zymodemes I and III). All three Entamoeba-positive subjects were asymptomatic cyst-passers. Antibodies to E. histolytica were detected in seven (1%) of the sera from the 550 patients examined; only one of these was a carrier of an E. dispar strain at the time of investigation. The low prevalences of all the parasitic infections and of the amoebic infections in particular (compared with those observed previously in institutions for the mentally retarded) reflect relatively good facilities and sanitary conditions, an adequate number of well trained staff and good control of the more susceptible subjects.